The Effect of Diethylstilbestrol and Methyltestosterone on
the Growth, Carcass Characteristics, and Nitrogen
Retention of Growing Swine
ERNEST W. LUCAS
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
I wish to extend thanks to my major professor, Dr. H. D.
Wallace, for guidance and advice during the course of the investi-
gation, as well as to Dr. Herb Brown of Eli Lilly and Company for
supplying the hormone material and participating in the taste
panel. The assistance of Drs. William Mendenhall and John Cornell
in statistical analysis is also gratefully acknowledged. wish
also to thank Dr. A. Z. Palmer and Roger West for their assistance
in obtaining carcass data, and Bill Stradtmann for help with the
laboratory analyses. The assistance of Mike Demaree and Jim
Standish, fellow graduate students, was indispensable during the
field work and collection of data.
Special and deepest appreciation is extended to my wife, Barbara,
for her encouragement and for typing the manuscript and drawing the
TABLE OF CONTENTS
ACKNOWLEDGEMENTS.......................... .................... 11
LIST OF TABLES................................................. v
LIST OF FIGURES...............................................** VI
ABSTRACT .......................... ............................ x
INTRODUCTION .................................................. 1
REVIEW OF LITERATURE ........................................... 3
The Effects of Sex on the Growth and Carcass
Quality of Swine. ............................ .............. 3
Sex Odor in Pork............................................ 6
The Effects of Estrogens on the Growth and
Carcass Quality of Swine..................................... 12
The Effects of Androgens on the Growth and
Carcass Quality of Swine ................................... 19
The Effects of Combinations of Androgens and
Estrogens on the Performance and Carcass
Quality of Swine........................................... 24
The Effects of Androgens on Protein Anabolism
in Animals.................................................. 28
The Effects of Diethylstilbestrol on Protein
Anabolism in Animals........................................ 30
The Mechanisms of Anabolic Action of Androgens
and Diethylstilbestrol..................................... 32
General Objectives ......................................... 35
General Experimental Methods................................. 35
Analytical Methods......................................... 40
TABLE OF CONTENTS (continued)
Statistical Methods........................................ 45
Experiment 178-A........................................... 46
Experiment 178-B............................................ 49
Experiment 178-C........................................... 53
Experiment 178-D........................................... 55
Experiments 178-E and F.................................... 58
GENERAL DISCUSSION ............................................ 61
The Effects of Hormone, Protein, and Sex on the
Feedlot Performance of Growing-Finishing Swine.............. 61
The Effects of Hormone, Protein, and Sex on the
Carcass Characteristics of Swine........................... 64
The Effects of DES + MT on the Nitrogen Retention
of Growing-Finishing Swine.................................. 70
The Effects oF DES + MT on the Excretion of Urinary
17-ketosteroids in Swine.................................... 72
General Comments............................................. 73
SUMMARY AND CONCLUSIONS........................................ 77
APPENDIX I: Tables............................................ 80
APPENDIX II: Figures.......................................... 110
LITERATURE CITED............................................... 149
BIOGRAPHICAL SKETCH ........................................... .157
LIST OF TABLES
Table No. Page
SWINE EXPERIMENT 178
1 Composition of diets................... 81
2 Calculated analysis of diets........... 81
3 Trace mineral premix................... 82
4 Vitamin premix......................... 82
5 Dry matter and protein % of diets...... 82
6 Code for marbling score, 1. dorsi...... 83
7 Code for color score, 1. dorsi ......... 83
8 Code for firmness score, 1. dorsi...... 84
9 Code for boar odor and flavor.......... 84
10 Experimental design.................... 85
11 Feedlot performance summary............ 85
12 Feedlot performance t test............. 86
13 Summary of responses ................... 87
14 Analysis of variance................... 88
15 Analysis of variance................... 89
16 Analysis of variance ..............".... 90
LIST OF TABLES (continued)
Table No. Page
17 Experimental design, growing phase..... 91
18 Experimental design, finishing phase... 91
19 Feedlot performance means, growing
20 Analysis of variance................... 92
21 Summary of responses................... 93
22 Analysis of variance................... 94
23 Analysis of variance................... 95
24 Analysis of variance................... 96
25 Experimental design.................... 97
26 Summary of responses................... 97
27 Analysis of variance................... 98
28 Analysis of variance................... 98
29 Analysis of variance................... 99
30 Analysis of variance.................... 99
31 Analysis of variance................... 100
32 Experimental design.................... 100
33 Summary of responses................... 101
34 Analysis of variance................... 102
35 Analysis of variance................... 103
36 Analysis of variance................... 104
37 Analysis of variance................... 105
LIST OF TABLES (continued)
EXPERIMENTS 178-E & F
Experimental design.................... 106
Suimary of responses ................... 106
Analysis of variance................... 107
Analysis of variance................... 107
Analysis of variance................... 108
Analysis of variance................... 108
Significant effects in 4 trials........ 109
LIST OF FIGURES
Figure No. Page
1 PxHxS interaction: dressing %.......... I11
2 PxHxS interaction: % lean cuts......... 112
3 Sex effect: % ham....... ........... 113
4 HxS interaction: % loin................ 114
5 Protein effect: % picnic............... 115
6 Hormone effect: % picnic............... 116
7 Hormone effect: % butt................. 117
8 PxS interaction: % butt................ 118
9 Protein effect: backfat thickness...... 119
10 Hormone effect: backfat thickness...... 120
11 Protein effect: loin eye marbling..... 121
12 Hormone effect: loin roast aroma and
13 Sex effect: daily gain................ 123
14 HxS interaction: daily feed........... 124
15 Hormone effect: feed/gain.............. 125
16 PxS interaction: dressing % .......... 126
17 HxS interaction: % lean cuts.......... 127
18 HxS interaction: % loin............... 128
19 PxH and HxS interaction: backfat
LIST OF FIGURES (continued)
Figure No. Page
20 PxHxS interaction: carcass length..... 130
21 Sex effect: loin eye firmness......... 131
22 *roae Cff 1- --Cz- -
23 HxS interaction: daily gain............ 133
24 Sex effect: daily feed................ 134
25 Hormone effect: daily feed............ 135
26 Hormone effect: feed/gain............. 136
27 Hormone effect: % lean cuts........... 137
28 HxS interaction: % ham................ 138
29 Hormone effect: % picnic.............. 139
30 Hormone effect: % butt............... 140
31 Hormone effect: backfat thickness..... 141
32 Sex effect: loin tenderness........... 142
33 Hormone effect: pork chop aroma and
34 Hormone effect: loin roast aroma and
35 Sex effect: 1. dorsi % dry matter..... 145
36 Hormone effect: 1. dorsi % protein.... 146
37 Sex effect: 1. dorsi % fat............ 147
38 Hormone effect: 1. dorsi % fat........ 148
Abstract of Dissertation Presented to the
Graduate Council of the University of Florida in Partial Fulfillment
of the Requirements for the Degree of Doctor of Philosophy
THE EFFECT OF DIETHYLSTILBESTROL AND METHYLTESTOSTERCNE
ON TH"E Gr CAR, CrASS C ilARACT-R-ISTICS, AND Nf;,iGEN RETENTGi N
OF GROWING SWINE
Ernest W. Lucas
Chairman: H. D. Wallace
Major Department: Animal Science
Experiments were conducted to determine the effects of a combi-
nation of 2.2 mg each of diethylstilbestrol and methyltestosterone
(DES + MT) per kg of feed on the feedlot performance, carcass charac-
teristics, and nitrogen retention of growing-finishing swine. The
interrelationships between hormone supplementation and dietary protein
level and sex were also investigated. A total of 6 trials, involving
205 crossbred pigs, were conducted. Of these, 4 were feeding and car-
cass experiments and 2 were metabolism trials. Practical corn-soybean
meal rations with 12, 14, or 16 percent protein were fed with and
without DES + MT to growing-finishing barrows and gilts.
Hormone supplementation caused a decrease in average daily gain
and average daily feed consumption, but improved feed conversion effi-
ciency. Protein level did not significantly affect feed intake, feed
efficiency, or rate of gain. Barrows ate more feed and gained faster
Carcass leanness was markedly improved by hormone supplementation.
Evidence of this was seen in an increased percentage of lean cuts,
both individually and as the 4 lean primal cuts, in pigs fed DES + MT.
There was also a decreased backfat thickness and increased carcass
length due to hormone supplementation. In addition, pigs fed higher
protein lpvelq were leaner than those fed Ic.waer protein levels. Gilts
were leaner than barrows.
Carcass subjective measurements were not affected by any treat-
ment. There was a significantly increased incidence of boar odor and
flavor in the meat of pigs fed DES + MT. This boar odor markedly
decreased the eating quality of meat of treated pigs in some cases.
Chemical composition of meat was significantly but not consistently
affected in 2 trials by DES + MT.
Nitrogen retention was not enhanced by feeding DES + MT in 2 ex-
Excretion of 17-ketosteroids in urine was significantly but not
consistently affected by hormone supplementation.
Interactions of hormone supplementation with both sex and protein
level were observed; these obscured some main effects. Interactions
affecting average daily gain, average daily feed intake, dressing
percentage, yield of lean cuts, average backfat thickness, average
loin eye area, and carcass length were observed.
The mode of action of DES + MT in improving carcass leanness was
not clear. The effects of hormone supplementation were not consistently
manifested in all trials, although there was in general a trend toward
decreased feed intake and rate of gain, increased feed efficiency, and
improved carcass leanness due to DES + MT. Although DES + MT can be
of significant benefit in improving feed conversion efficiency and car-
cass leanness, these benefits may be partially offset by the presence
of boar odor and flavor in the meat of some treated pigs.
The use of feed additives and chemotherapeutics in animal rations
for the purpose of improving performance and production is a topic of
continuing interest in the nutrition field. Experiments have been
conducted with all species of domestic livestock for the purpose of
developing, testing, and evaluating various chemotherapeutics for use
in livestock rations. Many of these compounds are in general use
Recent trends in consumer preference have focused attention on
the need for animals which will gain efficiently and produce lean,
meaty carcasses without excess fat trim.
About 20 years ago it was discovered that the addition of cer-
tain estrogenic substances to the rations of beef cattle in the feed-
lot produced beneficial responses in these cattle. Among the effects
were improved feed efficiency and gains, heavier muscling, increased
nitrogen retention and decreased fat deposition. It has become
standard practice to feed or implant this material, diethylstilbestrol,
to finishing cattle nearly everywhere in the U.S.
The advent of diethylstilbestrol feeding in cattle has sparked a
whole field of research involving hormone feeding, using most species
of domestic animals. Although the merits of diethylstilbestrol are
proven in the case of ruminants, the responses in monogastric species
have been somewhat varied. Several other estrogenic substances have
been investigated as potential feed additives, as well as numerous
androgenic compounds. Recently, work using combinations of estrogen
and androgen has been done.
Research with hormones as chemotherapeutics for swine has been
conducted since the early 1950's, with varying results. Evidence pro
and con has been collected for several different hormones, including
diethylstilbestrol and methyltestosterone, the most widely used estro-
gen and androgen, respectively. Recent work indicates that a combina-
tion of these two compounds fed to growing-finishing swine is more
effective in stimulating efficiency, carcass quality, and leanness
than either one alone.
The purpose of this study was to investigate the effects of a di-
etary combination of diethylstilbestrol (DES) and methyltestosterone
(I)T), fed at 2.2 my each per kg of feed, on the growth, carcass charac-
teristics, and nitrogen retention of growing-finishing pigs.
REVIEW OF LITERATURE
The Effects of Sex on the
Growth and Carcass Quality of Swine
Sex has been recognized for many years as a factor which affects
the performance of meat animals. Differences in growth, efficiency,
and carcass characteristics between the genders are common in most
species. Swine are prone to show sex differences in performance and
Blair and English (1965) reported on an experiment designed to
measure sex differences in growth and carcass quality in growing-
finishing pigs. These workers fed boars, gilts, and barrows on a
similar ration from weaning to market weight and measured carcass
parameters and feedlot performance. They reported significant differ-
ences among sexes in the various standard carcass parameters. Boars
had significantly less backfat than either barrows or gilts. In addi-
tion, boars and gilts showed a significantly larger loin eye area than
Wallace (1965) reviewed the effects of sex influences (barrows vs.
gilts) on finishing swine and concluded that gilts gained more slowly
but more efficiently than barrows, and that gilts were superior to
barrows in all aspects relating to carcass leanness.
Kolaczyk and Kotik (1966) compared muscle properties of barrows
and gilts. The meat of gilts had a significantly higher percentage of
moisture than that of barrows. Barrows exhibited significantly more
fat in the meat than gilts. No significant difference was observed
between barrows and gilts for nitrogen content of lean meat. Gilts,
however, had a significantly higher myoglobin level in the muscle
than barrows; as a result, the meat of gilts was significantly darker
than that of barr.ws.
Hale and Southweli (1967) measured differences in swine perfor-
mance and carcass characteristics due to dietary protein, sex, and
breed. They fed 60 weanling pigs in a 3 x 2 x 2 factorial experiment
to study effects of level of protein sequence (18 15%; 16 13%;
and 14 11%), sex (barrow and gilt), and breed (Duroc and Hampshire),
on performance and carcass traits of growing-finishing swine. Sex
differences were noted by these authors. They reported that barrows
gained significantly faster than gilts, but that gilts had a signifi-
cantly higher dressing percentage than barrows. In addition, the car-
casses of gilts were significantly longer, had less backfat, larger
loin eye area, and a higher percentage of lean primal cuts than those
Hale, Johnson, and Warren (1968) studied the effect of season,
sex, and energy level on performance and carcass traits of pigs. They
used 80 weanling Duroc barrows and gilts, and reported that barrows
consumed significantly more feed per day and needed more feed per unit
of gain than gilts. Gilts, however, yielded carcasses that were sig-
nificantly longer, leaner, had a larger loin eye area, and had a higher
percentage of lean primal cuts than barrow carcasses.
Swierstra and Rahnfeld (1968) studied growth, carcass measure-
ments, and sexual development of partially or completely castrated pigs.
They reported no differences-in rate of gain, age at slaughter, dress-
ing percentage, ham weight, loin eye area, average backfat thickness,
or carcass length between pigs partially castrated by Baiburtcjan's
method and pigs completely castrated.
Wong, Boylon, and Stothers (1968) performed an experiment to
study differences in performance and carcass traits of swine due to
sex and dietary protein level. One group of pigs containing equal num-
bers of boars, barrows, and gilts with an initial average weight of
22.5 kg was given a growing ration (17% protein) until slaughter at
an average weight of 88.6 kg. A similar group of pigs received the
growing ration to a body weight of 50 kg and then a finishing ration
(13% protein) until slaughter. No differences due to protein were
observed, but significant differences between sexes were found for
average daily gain and feed per unit of gain. Boars exceeded barrows
by 7 percent and gilts by 5 percent in average daily gain. Boars re-
quired 16 percent less feed per unit of gain than barrows. Gilts
exceeded boars and barrows in loin eye area. Both boars and gilts were
superior to barrows in percent lean in the ham face.
On the basis of the previously cited experiments, it seems reason-
able to conclude that there is a real sex difference in performance and
carcass quality in swine. When only performance and carcass objective
measurements are considered, boars rank superior to gilts, and gilts
rank superior to barrows. In light of the differences observed between
the sexes in performance and carcass traits, it seems logical to assume
that the cause of these differences might be due to the presence or
absence of the natural sex hormones produced'in the gonads.
Sex Odor in Pork
Castration of male farm animals is a practice which is nearly as
old as the domestication of animals. Benefits originally sought were-
those of greater tractability in work animals. Physiological changes
and ensuing material developmental changes occur in animals following
castration. The effect of castration on growth, feed efficiency, car-
cass traits, and meat quality rust be weighed against the inherent
advantages in growing uncastrated males. Literature previously cited
shows that there might be an economic advantage, in addition to
breeding and selection advantages, in feeding intact boars.
In swine, however, the phenomenon known as "sex odor," "boar
odor," or "taint" occurs to some degree in the fat and meat of intact
males. Martin (1969), in a review of the sex odor problem in pork,
documents cases of sex odor in boars as far back as 1936. This odor
or flavor has caused a discrimination by packers and consumers against
the meat of intact male swine. In spite of the advantages in perfor-
mance and carcass traits which boars exhibit, it is not economically
feasible to feed boars.
In his review, Martin (1969) notes that comprehensive studies
of carcasses of pigs of all sexes, conducted at commercial slaughter-
houses, showed that 17 percent of all hogs, regardless of sex, exhibit-
ed medium to strong sex odor. The problem is not confined to boars.
This observation is corroborated by Wil liams, Pearson, and Webb (1963),
who studied the incidence of sex odor in boars, sows, barrows, and
gilts. Incidence of sex odor was studied using fat samples from the
flank area or ham facing of 79 boars, 78 sows, 86 barrows, and 96 gilts.
Results indicated that the occurrence of sex odor was largely, but not
exclusively, dependent on the sex of the animal. Boars were found to
have 64 percent incidence of sex odor, significantly higher than any
other group tested. No significant differences could be found between
the percent incidence of sex odor in sows, barrows, and gilts, which
were found to have 1 percent, 5 percent, and 5 percent incidence,
Blair and English (1965) reported significantly more boar odor in
boar meat and fat than in barrow or gilt meat and fat, but were unable
to demonstrate any differences in flavor.
Charette (1961) indicated little or no undesirable odor in boar
Martin, Freden, and Stothart (1968) evaluated the quality of
cooked pork from 144 pigs consisting of an equal number of barrows,
boars, gilts, and ridglings which ranged from 87 to 93 kg live weight
at time of slaughter. Ham steaks, prepared and cooked by a standard
procedure, were evaluated for cooking aroma, tenderness, juiciness,
texture, flavor, and overall preference by a panel of 6 trained judges.
Samples were scored on a 1 to 10 hedonic scale with 10 representing the
most favorable score. For tenderness and texture, the samples from
boars ranked highest, followed by gilts, barrows, and ridglings. All
sex differences were significant for these two characteristics. Rank-
ing for overall score and overall preference by judges was in this same
order. Samples from barrows and ridglings scored higher for cooking
aroma than samples from boars and gilts, although only 3 boars and 1
gilt were judged unacceptable. However, the authors noted that aroma
was not highly correlated with flavor, and samples which scored low on
aroma were often quite acceptable for flavor.
Craig and Pearson (1959), in a preliminary study on sex odor in
pork, reported that sex odor was strongest in the parotid gland, fat,
testicles, penis, and preputial diverticulum. The study was conducted
on the tissues of an 18 month old boar. They noted that fat or lean
with intramuscular fat produced boar odor when heated to the boiling
point in water. A barrow control failed to produce boar odor upon
heating. Ether extraction of the freeze-dried lean tissue produced an
extract which appeared to contain the odor component, which the extrac-
ted lean did not. Ether or carbon tetrachloride extracted fat did not
give off sex odor when heated. This led the authors to conclude that
sex odor in pork is found only in the fatty tissues and that the odor-
contributing elements may be separated from the fat by a selective
In another study, Craig (1960) was unable to detect sex odor in
any aqueous distillation condensates of boar fat, although a strong
sex odor was evident in the rat prior to distillation. This further
demonstrated the lipophilic nature of the sex odor component. Fat
from boars did not differ significantly from that of barrows with re-
gard to nitrogen content.
Craig (1961), in a dissertation abstract, reported that the
odor component of boar fat was not readily voldtilized below 100" C.
lie was unable to isolate the component from any solvent fraction by
Craig, Pearson, and Webb (1962) reported the findings of a series
of experiments to fractionate the components responsible for sex odor
in pork. They noted that sex odor was produced when fat, lean with
fat in it, and most organs from a boar were heated in a skillet or in
hot water. Odor volatilized most greatly at 100 to 1080 C, but was
not entirely absent at body temperature. The sex odor component was
found to be water insoluble, ether soluble and definitely associated
with the fatty tissues of boars. The odor was absent in reconstituted
moisture-free, fat-free lean tissue. Distillation methods were
regarded as unsuccessful in collecting sex odor components in any
recognizable form. No differences in distillates of boar and barrow
fat were detected by heat tests or gas chromatography. Cold saponi-
fication of boar fat yielded a small amount of unsaponifiable matter
which produced a concentrated, permeating sex odor on heating. The
authors concluded that the agents responsible for sex odor are located
in the unsaponifiable fraction of boar fat. Cholesterol and squalene
were found in this fraction of both boar and barrow fat, but sex odor
was not produced when either of these compounds was heated.
Patterson (1566) isolated large amounts of para-cresol, a metabo-
lite of tyrosine, from the phenolic fraction of boar preputial fluid.
It was not concluded that para-cresol was directly responsible for the
characteristic sex odor of heated boar fat, although it does contribute
significantly to the odor of the live boar and its immediate environ-
In a second paper, Patterson (1968a) identified a derivative of
the male sex hormone as the odor component in boar fat. This substance,
5-a-androst-16-ene-3-one, is a lipophilic ketone, and is found in the
fat of mature boars. This compound was found to have the empirical
formula C19H280, differing from the male hormone testosterone only by
a single oxygen atom and from androsterone by the elements of a mole-
cule of water. The author concluded that the source of the odor com-
ponent was a metabolite of the male sex hormones.
Patterson (1986b) later shed more light on the pathway of forma-
tion of the boar odor component. A musk odor compound, 3-a-hydroxy-5-
a-androst-16-ene, was isolated from the submaxillary salivary glands
of all boars tested, but not from the glands of barrows or gilts.
This secondary alcohol is a musk odor compound distinctly different
from the ketone previously isolated from boar fat. The alcohol was
successfully oxidized in vitro to the ketone, and the odor changed
from a musk to a boar taint. Since male sex hormones, the musk odor
alcohol, and the boar odor ketone all are so similar in structure, the
author concluded that both odor compounds were under testicular con-
trol. A pathway by which testosterone could be transformed to 3-0-
hydroxy-5-a-androst-16-ene was suggested. The B epimer also possesses
musk odor activity, but the a epirnr is much stronger. It may be that
epir-erization of the B compound to the a epimer occurs, since salivary
glands of boars contained almost exclusively the a substance.
Patterson (1968b) suggested an interesting hypothesis as to the
means of incorporation of boar odor into the fat of boars. He observed
that it was possible to detect the presence of the musk odor alcohol
in the submaxillary glands of young boars before the boar odor ketone
appeared in the gland or fat, and that the detection of the ketone,
as well as the alcohol, in the salivary glands of older boars shows
that the ketone is formed by the oxidation of the alcohol at a later
stage of maturity. He noted that the concentration of androstenol was
relatively high in the salivary gland of mature boars compared to the
androstenone concentration, but that in depot fat the opposite was
true. This observation led him to suggest that the submaxillary sali-
vary gland is either the site of formation of the androstenol, or that
it acts as a reservoir for the substance, presumably extracting it
from the bloodstream. He also noted that musk odors are known sex
attractants and that either androstenol or androstenone in the saliva
may act in this capacity. The sexual behavior of boars and sows
suggests an attractant of some kind present in the head of the boar.
Since the saliva was found to possess the odor of 5-a-androst-16-ene-
3-one, ingestion of the ketone in the saliva will result in its incor-
poration into the body as a result of the normal digestive process.
Because of its ketone structure, deposition in adipose tissue will
occur preferentially to other tissues. The hydrophilic alcohol, on
the other hand, will be eliminated from the body in:its normal water-
soluble state. This would explain the presence of the androstenone
but absence of androstenol in the depot fat of mature boars.
Weir et al. (1962) reported on a study of the composition and
organoleptic properties of pork chops as affected by cooking procedures.
They noted an increased percentage of fat on a dry weight basis for
the lean of cooked chops over the lean of raw chops. This was due to
migration of external fat into the meat during cooking. The authors
suggested that the phenomenon may be of some significance in the odor,
flavor, and texture of cooked meat.
From the evidence presented in the papers previously cited several
conclusions regarding sex odor may be drawn.
Research has shown that boar odor appears to be sex-limited and
associated with the presence of a ketone derivative of testosterone,
found in the fatty tissues of tainted carcasses.
All factors affecting the incidence of boar odor are not yet known,
but stage of maturity is very important. Incidence of boar odor is
high in mature boars and very low or nil in boars slaughtered at 70 kg
live weight or in boars which reach conventional slaughter (90 kg) at
a young age.
The assumption that all boar carcasses contain taint is invalid,
as well as the assumption that all barrow and gilt carcasses do not
The Effects of Estrogens on the
Growth and Carcass Quality of Swine
Diethylstilbestrol (DES), a synthetic estrogen, came into vogue
as a feed additive for cattle in the late 1940's and early 1950's.
During this period a number of workers began feeding or implanting
estrogens and other humoral substances in several species of domes-
tic livestock in an attempt to realize benefits similar to those ob-
tained in cattle supplemented with DES.
Woehling et al. (1951) were among the first workers to study
the effects of DES on swine. These workers fed 42 growing-finishing
pigs on a standard ration. Treatment was applied by subcutaneously
implanting 2 lots of 7 pigs each with 12 rg of DES at the start of
the experiment and again at 12 weeks. Pigs averaged 19.5 kg at the
start of the experiment and were slaughtered as they reached 95 kg.
Average daily gain, average daily feed intake, feed required for each
unit of gain, dressing percentage, carcass length, weight of ham,
loin eye area, and backfat thickness were among the characteristics
studied. These workers reported no significant differences due to
DES in any of these parameters.
Oinusson, Klosterman, and Buchanan (1951) implanted 12 or 25 mg
of DES in barrows and gilts. Average initial weight was 20 or 45 kg.
These workers did not observe any response in rate of gain or carcass
parameters due to DES. They did report, however, that DES implanted
hogs required 5 to 14 percent less feed per unit of gain than control
Pearson et al. (1952) conducted 3 experiments to determine the
effects of DES implants on average daily gain, feed efficiency, and
carcass characteristics of growing-finishing swine of different sexes.
Barrows, gilts, and boars weighing 16 or 42 kg initially were sub-
cutaneously implanted with DES. Level of dosage used was 25 mg
initially, 25 mg again at I month, and 50 mg at 2 months. These
workers reported no significant difference in rate of gain of barrows
or gilts caused by implanting DES, but there was a growth depression
in young implanted boars. No effect on feed efficiency due to DES was
observed. No differences in backfat thickness, carcass grade, or ten-
derness were apparent. DES had little or no influence on acceptability
ratings of pork loin roasts and did not appear to increase the eating
qualities of boar meat.
Beeson et al. (1955) conducted an investigation with barrows and
gilts weighing 20 kg initially, and fed a practical ration containing
DES in a quantity to supply 2 mg per animal per day. The treatment
did not improve growth rate or feed efficiency. There was a trend
toward leaner carcasses in the pigs fed DES, but no significant dif-
ferences were observed.
Taylor et al. (1955) studied the effects of orally administered
sciibescroi at levels of 0, 22, 44, 88, i76, 352, 704, 1408, or 28i6
pu of DES per kg of feed on the growth, carcass traits, and organ
development of growing-finishing pigs. A total of 120 pigs averaging
15 kg initially was finished to a terminal weight of 91 kg. No
differences in average daily gain or feed conversion were observed due
to feeding DES. Carcass differences were not significant. Stimulation
of female secondary sexual characteristics was observed in the devel-
opment of certain organs in both barrows and gilts.
Heitman and Clegg (1957) used 136 barrows and gilts in 4 experi-
ments and compared untreated pigs with pigs implanted with 30 or 60
mg of DES. Implanted pigs showed reduced gains, improved feed effi-
ciency, less backfat, and a greater percentage of lean primal cuts
than untreated pigs. The authors postulated that a possible protein
anabolic effect due to stilbestrol implantation could be causing the
increased carcass leanness.
Sewell, Warren, and O'Mary (1957) fed barrows and gilts averaging
18 kg initially to determine the effects of DES supplied orally at
levels 0, 1.1, 4.4, or 5.5 mg per kg of feed. They reported that gains
were not affected consistently in 3 different trials by DES supplemen-
Cahill et al. (1959) studied the influence of implanting stil-
bestrol on the carcass composition of boars, barrows, and gilts at
3 stages of maturity. They reported that stilbestrol implants of
1.5, 3.0, or 6.0 mg at 68 kg body weight had little effect on growth
rate or feed conversion ratio. They noted that a positive correlation
existed between level of DES implanted and both size of loin eye and
percentage of lean primal cuts.
Day et al. (1960) conducted a trial to determine the effects of
diethylstilbestrol and a combination of progesterone and estradiol on
growing-finishing swine. Poland China barrows were fed to market
weight on a practical diet. Treatments were administered by implant-
ing 6 mg of DES,.166.7 mg of progesterone plus 3.3 mg of estradiol
benzoate, or 500 mg of progesterone plus 10 mg of estradiol benzoate.
Differences in rate and efficiency of gain among the 4 treatment
groups were not statistically significant. Backfat thickness was
generally reduced by the hormone treatments, with both levels of the
progesterone-estradiol combination showing a significant effect.
Backfat probes for the 4 treatments averaged 3.91, 3.76, 3.56, and
3.45 cm respectively for the control, DES, low level progesterone-
estradiol, and high level progesterone-estradiol treatments. Carcasses
of pigs administered the high level of progesterone-estrogen treat-
ment had the lowest percentage of fat and highest yield of lean, evi-
denced by a significantly higher percentage of lean primal cuts,
larger loin eye area, and lower backfat thickness than other treatment
Beacom (1963) studied the effect of stilbestrol and estradiol-
testosterone implants on performance and carcass traits of market
swine fed different finishing diets. He reported no differences in
growth rate between control pigs and implanted pigs, but hormone
implants significantly decreased average daily feed intake. Carcass
parameters exhibited no significant differences bct;ccn control and
Gorrill, Bell, and Williams (1964) reported on an experiment
designed to measure the effects of DES implantation on the performance
of pigs on a restricted feeding regimen. Pigs weighing 50 kg ini-
tially were implanted with 12 mg of DES and finished to 91 kg. Im-
plantation with DES reduced barrow average daily gain from 0.69 kg
to 0.62 kg, but had no effect on gilt average daily gain. Feed intake
of barrows was reduced from 2.72 kg to 2.41 by DES, but gilt feed
intake was affected in the reverse manner, going from 2.27 kg to
2.45 kg. Implanted gilts digested protein better than did control
gilts, but the opposite was true for barrows. Loin eye area and back-
fat thickness were only slightly affected by DES, although the trend
was favorable in both cases.
Teague et al. (1964) conducted 7 trials to determine the effec-
tiveness of implanting boars with DES as a method for overcoming or
delaying the development of the odor or flavor commonly associated
with boar meat, and for retaining or further improving the favorable
performance and muscling characteristics of the boar. The feedlot
performance and carcass traits of market barrows, boars, and boars
implanted with 48 mg of DES at 70 kg or 96 mg of DES at 65, 70, or
75 kg were compared. Boars implanted with 96 mg of DES at 70 kg had
a significantly faster rate of gain than other groups. Feed conver-
sion was also favorably affected in this same group. The authors
found that carcasses of barrows were significantly shorter and fatter
than those of either boars or implanted boars. Sex odor and flavor
in the 10th rib chops were significantly reduced by implantation with
DES. In addition, no carcasses of boars implanted with DES were con-
demned for odor or flavor.
Plimpton (1966) implanted boars with 96 mg of DES at 70 kg and
fed them to 136 kg to determine the effects of the drug during extend-
ed growth on carcass composition, muscle quality, and palatability
of meat. Average daily gain and percentage of lean primal cuts were
significantly increased in implanted boars. Sex odor in meat of im-
planted boars was significantly reduced. No differences were observed
in marbling or color of the loin eye. Chemical evaluation of the loin
eye muscle showed no difference due to DES except percentage of mois-
ture and fat. Implanted pigs had significantly more moisture and
less fat in the lean of the longissimus dorsi muscle.
Plimpton et al. (1967) studied the performance, carcass traits,
and carcass composition of barrows, boars, and boars implanted with
96 mg of DES measured from live weight of 70.4 kg to 136.1 kg. Car-
cass measurements were related to treatment, age, time of slaughter,
and carcass weight. Implantation of boars with 96 mg of DES at 70.4
kg increased rate of gain and rate of lean primal cut deposition.
The rate of deposition of lean cuts was increased in implanted boars,
compared to control boars, for 10 of the 12 weeks following
implantation. This period also coincided with the time during which
DES significantly repressed sex odor in treated boars. All boars,
regardless of treatment, had carcasses significantly longer, leaner,
and with a higher yield of lean primal cuts than the carcasses of lit-
termate barrows of the same weight. A trend toward increased loin
eye area due to DES was observed. The yield of edible portion of
ham from boars was significantly more than that from barrows, and
the percentage of fat in the ham was also significantly lower for
boars. -Measures of growth such as loin eye area, carcass length, and
percentage of lean primal cuts were observed to increase in a linear
fashion with increasing age and weight. Differences in carcass com-
position were related to changes in weight.
Echternkamp et a]. (1969) studied the relationship between in-
tensity of boar odor and flavor and glandular development in normal
and DES implanted boars. They reported that implanting 96 mg of DES
at 70.3 kg significantly reduced the incidence of boar odor and flavor
to a live weight of 127 kg. In addition, DES significantly increased
average daily gain up to 104 kg and decreased the weight of accessory
sex glands. These authors also reported that there was a high corre-
lation between odor and flavor scores. They concluded that DES pre-
vented or delayed the development of boar odor and flavor.
Hale and Johnson (1970) fed ih4 weanling Duroc barrows individ-
ually to study the effects of season (summer vs. winter), energy con-
centration (high vs. low), and orally administered hormones (none,
diethylstilbestrol, or methyltestosterone), on performance in the
feedlot and on carcass characteristics of the pigs. The only
significant effect of feeding 2 mg of DES per day was a 2 percent
increase in the weight of the lean primal cuts.
The papers previously cited provide a general picture of the
effect of estrogens, notably diethylstilbestrol, on the performance
and carcass characteristics of swine. Although different workers have
observed conflicting results in some cases, an overall trend is appar-
ent. Treatment with DES generally reduces feed intake and improves
feed conversion. Growth is usually depressed in barrows and gilts,
but may be increased in boars. There seems to be a definite improve-
ment in carcass leanness in all sexes. DES has also shown ability
to suppress or delay the development of boar odor or flavor, at least
up to 100 kg of body weight. Benefits in feed efficiency and lean-
ness due to DES are not apparent in younger pigs, but in pigs from 45
kg to market weight, DES can be of some value in improving efficiency
The Effects of Androgens on the
Growth and Carcass Quality of Swine
Researchers have long known that males generally produce leaner,
more heavily muscled carcasses than do females or castrate males.
Literature previously cited documents sex differences in growth and
carcass quality in swine. Researchers have attempted to produce
this increased leanness and muscling in females and castrated males
by replacement therapy with testosterone since the early 1950's.
Woehling et al. (1951) implanted 30 mg of testosterone in 20 kg
barrows and gilts at the start of the experiment and again at 12 weeks.
They were unable to demonstrate a response in any performance or car-
cass parameter due to testosterone therapy.
Noland and Burris (1956) fed methyltestosterone (MT) at a level
of 0, 0.015, 0.15, or 1.5 rng per kg of body weight to boars, barrows,
gilts, and castrated gilts. They noted that the rate of body weight
gain of females was slightly depressed by 0.15 mg of MT per kg of body
weight, but gains of males were not affected. All sexes fed MT had
leaner carcasses, evidenced by a higher percentage yield of lean
primal cuts, compared to control pigs. The authors noted that boars
fed the highest level of MT exhibited markedly depressed spermatogene-
sis, and interstitial tissue development in all boars fed MT was
depressed. They concluded that the levels of MT fed were not effec-
tive in inducing any growth stimulus.
Bratzler et al. (1954) made carcass comparisons of boars, tes-
tosterone implanted barrows (193 mg of testosterone per pig), and
barrows castrated at 18, 45, 64, or 82 kg. Boars and 82 kg castrates
had a higher percent of lean in the rough loin, less backfat, longer
carcasses, and a higher live weight and lean primal cut yield.
Quality of boar pork was judged unacceptable in palatability tests
for odor and flavor, but no difference in palatibility of chops be-
tween control barrows and barrows implanted with testosterone pro-
pionate was observed.. In this trial no differences due to
testosterone or castration were observed in rate or gain or feed con-
Beeson et al. (1955) administered 20 mg of MT per pig per day
in a practical ration to barrows and gilts fed from 23 kg to market
weight. Growth rate and feed efficiency were unaffected, but car-
casses from testosterone fed pigs contained heavier lean cuts (ham,
loin, Boston butt, picnic shoulder) and lighter fat cuts (fat backs,
bellies, jowls) than carcasses from control pigs. The percentage yield
for lean primal cuts was 62.4 percent for testosterone fed pigs and
58.8 percent for control pigs. Chemical analysis of carcass composi-
tion showed 5 percent less fat and 5 percent more lean in testoster-
one fed pigs than in control pigs.
Perry et al. (1956) tested the effect of various levels of orally
administered MT (0 to 62 mg of M1T per pig per day) on the growth and
carcass composition of growing-finishing barrows and gilts fed from
23 kg to market weight. They reported that a daily intake of 27 mg
or more of MT resulted in a highly significant growth depression, but
also resulted in decreased fat deposition evidenced by decreased
Johnston, Zeller, and Hiner (1957) fed MT to swine at levels of
20 or 33 mg of MT per kg of feed. In 5 experiments they noted that
MT decreased rate of gain, average daily feed intake, backfat thick-
ness, and feed efficiency. There was no odor or flavor problem
reported in the meat of testosterone supplemented pigs. The authors
concluded that MT increased the ratio of lean to fat in the carcasses
Whiteker et al. (1959) studied the effects of various androgens
at different levels on growth and carcass traits of pigs. They fed
96 barrows and gilts in 3 trials on practical diets containing either
methyltestosterone, methylandrostenediol, thyroprotein, or a combination
of the latter two. Rate of gain was not significantly affected by
any of these additives. Pigs fed the combination of methylandrostene-
diol and thyroprotein produced significantly leaner carcasses than
did those pigs fed either drug singly. Pigs fed MT produced carcasses
that had a significantly higher percentage of lean than did pigs fed
the basal ration. None of the treatments caused an adverse flavor
or odor in the meat. Loin protein content was not significantly
affected by any of the treatments. Masculine behavior and character-
istics were noted in the animals receiving MT.
Thrasher et al. (1959) conducted 3 experiments to determine the
effects of various testosterone analogs, combinations of testosterone
and stilbestrol, and late castration on the performance and carcass
quality of swine. No differences due to treatment were observed in
any parameter tested, although there was a trend toward increased
leanness in pigs fed MT singly or in combination with DES.
Baird and McCampbell (1959) reported no differences in feedlot
performance or carcass quality in pigs fed 0.55 mg of hydroxyzine per
kg of feed. Another test comparing androgenic compounds with DES,
estradiol-progesterone, and a basal ration failed to show any signifi-
cant differences due to any treatment. Other combinations of hormones
and tranquilizer substances were tested and they also failed to pro-
duce any changes in growth or carcasses of swine.
Cantwell, Johnston, and Tabler (1962) fed swine methyltestoster-
one and 17-ethyl-19-nortestosterone under various experimental con-
ditions to determine their effects on growth and carcass character-
istics, with special emphasis on glands and internal organs.
Methyltestosterone and 17-ethyl-19-nortestosterone fed at 20 to 33 mg
per kg of feed singly and in combination with stilbestrol at 13 mg
per kg of feed caused highly significant increases in weight of
liver, kidney, heart, and thymus gland. Average daily gain was
decreased significantly, as was adrenal gland weight. The authors
reported that methylstestosterone was more potent than 17-ethyl-19-
Mlente et al, (1962) studied the effect of 9-fluoro-ll-hydroxy-
17-methyltestosterone (Halotestin), a testosterone analog of great
potency. Barrows and gilts weighing 32 to 57 kg were fed 0 to 27.5
mg of Halotestin per kg of diet. They reported a significant decrease
in backfat thickness, and an increase in percent yield of lean primal
cuts due to Halotestin. Gains were depressed in pigs fed the hormone
compared to gains of those fed the basal diet.
Hale and Johnson (1970) fed weanling pigs methyltestosterone at
a level of 20 mg per day. They reported that MT decreased rate of
gain, daily feed intake, dressing percentage, and backfat thickness,
but increased carcass length, area of loin eye, and weight of the
4 lean cuts. They concluded that methyltestosterone had a potent
anabolic action in swine, evidenced by the increased leanness in car-
casses of pigs fed MT.
The previously cited papers present a review of the effects of
androgenic compounds on the growth and carcass characteristics of
swine. Of all androgens in use, methyltestosterone is probably one
of the most practical and anabolically potent. There seems to be
rather strong evidence that lIT is capable of inducing in swine
measurable carcass changes in a favorable direction. These papers
indicate that pigs fed methyltestosterone gain more efficiently, and
produce leaner, meatier carcasses than do pigs fed normal rations.
There is some evidence that high level testosterone therapy may pro-
duce significant odor or flavor problems in pork.
The Effects of Combinations of Androgens and Estrogens
on the Performance and Carcass Quality of Swine
Research has indicated that there is some benefit to be derived
from feeding or implanting estrogens or androgens in growing swine
of all sexes. Although changes in performance and carcass are not
always great or drastic, there is nevertheless a definite trend to-
ward decreased feed consumption and increased carcass leanness due
to hormone therapy. Since estrogen supplementation has shown partic-
ular usefulness with regard to boars, some workers feel that using
the combination of androgen and estrogen in barrows'and gilts would
prove more beneficial than either compound used singly. Work has
been done using combinations of estrogenic and androgenic drugs to
determine if the effects of the two substances used together are
Thrasher et al. (1959) studied combinations of testosterone and
stilbestrol and their effects on carcass quality and feedlot perfor-
mance in growing-finishing pigs. In 3 trials involving a total of 180
pigs they reported a non-significant trend toward increased carcass
Beacom (1963) implanted finishing pigs with a combination of
estradiol and testosterone. He observed no difference In growth
rate between controls and treated pigs, but there was a significant
decrease in average daily feed consumption caused by the estradiol-
testosterone implant combination. Beacom also reported an increase
in 'oin eye died in Lreated pigs fed a low energy diet. Other
indices of carcass leanness were favorably improved.
Wallace et al. (1967) conducted a 2 x 2 x 2 factorial experiment
involving protein level, sex, and supplementation with a combination
of DES and MT. The trial involved 48 pigs which averaged 59 kg
initially. The pigs were slaughtered as they reached 95 kg. Feedlot
performance and carcass characteristics were studied. Hormone supple-
mentation with DES + MT significantly decreased average daily gain,
average daily feed intake, and average backfat thickness. In addition,
there was a significant interaction between protein level and hormone
supplementation for average feed conversion ratio, which was inter-
preted as evidence that hormone supplementation favored improved feed
conversion in the presence of increased protein. Secondary sex glands
in barrows (Cowper's gland, prostate gland, and seminal vesicles) and
ovaries and uteri in gilts were markedly affected by hormone supple-
mentation. All these organs exhibited hypertrophy in hormone
supplemented pigs. Loin roasts were checked for any Indication of
boar odor or flavor. A strong influence on odor and flavor of pork
was exerted by DES + MT. The meat from some hormone fed pigs had a
very undesirable odor and flavor when cooked. Both gilts and barrows
were affected to the same degree. The authors concluded that the
odor was probably due to methyltestosterone.
Baker et al. (1967) fed 448 finishing pigs in 3 trials to eval-
uate the effects of a dietary combination of DES + MT. The effects
of sex and dietary protein level on hormone response were also
studied. Regardless of sex or protein level, carcass leanness was
improved by DES + MT. Improved feed efficiency due to hormone,
however, resulted only at higher levels of protein. These workers
also observed that feed efficiency and carcass leanness response to
DES + MT was greater in barrows than in gilts. Growth rate and feed
conversion efficiency were greatest at a dietary protein level of
12 percent in barrows and 14 percent in gilts, but for maximum carcass
leanness response, barrows needed 14 percent protein and gilts re-
quired 16 percent. Protein level did not appear to affect backfat
thickness in any of the trials, but the remainder of carcass lean-
ness parameters were improved additively by both DES + MT and increased
Baker, Diller, and Jordan (1968) observed that DES + MT caused
a lowering of serum triglycerides level when fed to gilts. This de-
crease did not occur in barrows. Serum cholesterol and free fatty
acids were not affected by hormone treatment. The mechanism by which
DES + MT decreased serum triglycerides in gilts was not elucidated.
Doornenbal and Frankenham (1969) studied growth, feed conversion
ratio and chemical composition in market weight barrows and gilts fed
DES + MIT plus tylosin. They reported a trend toward increased gains,
improved feed efficiency and a reduction in age to market. Carcass
measurements within sex were not significantly different between
controls and hormone fed animals. There was a trend toward increased
leanness in barrows, but toward increased fat deposition in gilts.
The authors concluded that different proportions of sex steroid hor-
mones would be required for barrows and gilts to achieve equally
beneficial effects on carcass composition.
Heyer et al. (1968) evaluated the effects of a dietary combina-
tion of DS + I T onr the reproductive performance of gilts fed 2.2 Or
4.4 mg each of DES and MT per kg of diet during the finishing phase
only, or continuously through finishing to breeding. A total of 136
gilts was used in 5 experiments. These workers reported that feeding
the hormonal combination through breeding inhibited estrus. Some
gilts conceived after termination of hormone feeding. Gilts which
received the hormone only during the finishing phase had normal estrus
cycles and conception was reduced in only 1 of 3 experiments. In
4 out of 5 experiments, DES + MT reduced litter size. It was noted
that gilts fed the hormone supplement during finishing farrowed smaller
litters at the first two farrowings. Litter size increased to that
of the control group by the third parturition. The authors concluded
that inhibition of the normal reproductive function by DES + MT treat-
ment during the finishing period did not seem to be permanent. The
lower level of hormone addition was not as inhibiting to reproduction
as the high level.
Evidence accumulated by various researchers whose work was re-
viewed in the foregoing section indicates that there may be some addi-
tive performance and carcass improvement when estrogens and androgens
are fed or implanted in combination. The overall trend is much the
same as that observed when either type of drug is fed or implanted
alone. Combining the two substances seems to produce a more power-
ful stimulus to the metabolism of the animal, resulting in the changes
in feedlot performance and carcass composition reported. The entire
picture is unclear as yet regarding the mechanism of action of these po-
tent humoral substances. Also, observed responses to these drugs
are not always consistent in swine. It does appear, however, that '
there may be some benefit to be derived in feedlot performance in-
crease and in favorable changes in carcass characteristics by supple-
menting growing-finishing pigs with a combination of estrogen and
There do not appear to be any permanent adverse effects on
reproductive capacity of gilts fed DES + MT through the finishing
The Effects of Androgens on
Protein Anabolism in Animals
The influence of androgens on nitrogen retention has been known
since 1935 (Dorfman and Shipley, 1956) when it was discovered that
extracts of urine containing androgenic material stimulated nitrogen
retention in dogs.
Drill and Saunders (1956) used rats to test the ratio of anabolic
to androgen activity in a number of steroids. Of the testosterone
analogs tested, 17-ethyl-19-nortestosterone was found to be the most
potent anabolically and also to have the highest ratio of anabolic to
androgen activity. This compound was reported to be 5 times more
anabolically active than 17-a-methyltestosterone when administered
orally to rats, while the androgenic activity of methyltestosterone
was relatively high.
Leathem (1956), in a rat experiment, found that the state of
body protein stores at the time of hormone administration determined
in large part whether or not an anabolic response was observed.
Older rats and protein depleted rats exhibited a marked increase in
nitrogen retention when testosterone or other anabolic steroids were
administered. Very little response in young, healthy rats fed high
protein diets was observed. Leathem concluded that in many instances
nutrition appears to be dominant over anabolic hormones, even though
steroids are known to be involved in protein anabolic processes.
Applezweig (1962) reported on radioisotope studies In which rats
were fed 15N-labeled glycine with and without androgen therapy. An
increase in amount of 15N-labeled glycine retained was apparent for
the treated group. The author concluded that androgen influenced the
reaction of amino acids +-* proteins and caused the reaction to pro-
ceed in favor of protein synthesis. He postulated that either an
inhibition of protein catabolism or a stimulation of anabolism could
be the mechanism of action. In addition, Applezweig stated that when
body protein stores were filled, little or no anabolic response to
androgen treatment was observed.
Robinson and Singleton (1966) tested the effects of norbolethone,
an anabolic steroid, on the performance and body composition of
barrows. They used 24 Large White barrows fed two levels of protein
with and without 0.1 mg of steroid per kg of body weight. On the
low protein diet, steroid therapy increased growth, but the opposite
was true for the high protein diet. This interaction was significant.
In addition, there was a significant improvement in percentage of
lean in the carcass and loin eye area, but a decrease in carcass
Evidence presented in the papers previously cited indicates
that there is a definite protein anabolism in animals following
therapy with certain steroid hormones. Response varies according to
species, age, nutritional status, and sex of the animal. In general,
steroid anabolism is most marked in those animals in a state of
The Effects of Diethylstilbestrol on
Protein Anabolism in Animals
Researchers have attempted to determine the mechanism of action
of diethylstilbestrol in stimulating growth. There is a general
agreement that increased nitrogen retention due to protein anabolism
occurs in ruminants consistently, and to a more variable degree in
monogastrics. The exact means by which DES causes this remain un-
Clegg (1952) reported on the use of DES to increase nitrogen re-
tention in steers. The nitrogen retention of steers implanted with
60 mg of DES was more than twice that shown by control animals.
Jordan and Bell (1952) studied nitrogen retention in lambs im-
planted with 12 mg of DES. Hormone implantation did not appear to
alter digestion of feed or nitrogen retention.
Whitehair, Gallup, and Bell (1953) implanted lambs with 24 mg
of DES to study the effects on calcium, phosphorus, and nitrogen
balance. There was no difference in the digestibility of feed be-
tween implanted and control lambs, but DES caused a significant In-:
crease in the amount of calcium, phosphorus, and nitrogen retained.
DES implanted lambs also showed faster rates of gain than control
Tillman and Brethour (1955) fed lambs 6 or 10 percent protein
with and without 3 mg of DES per day to study the effects on calcium,
phosphorus, and nitrogen metabolism. Nitrogen retention and average
daily gain were decreased by DES in the 6 percent protein ration,
but the reverse was true for the 10 percent protein ration. The
authors concluded that the effects of DES were not consistent.
Struempler and Burroughs (1955) studied the effects of growth
hormone and DES on nitrogen retention in lambs fed low or high energy
and low or high protein diets. Growth hormone or DES alone resulted
in increased nitrogen retention, regardless of dietary energy or pro-
tein level. When administered together, however, growth hormone and
DES did not produce an additive response. The authors concluded that
DES may cause an increase in secretion of growth hormone in the
Sell and Balloun (1961) studied nitrogen retention of growing
cockerels as influenced by DES or MT. DES resulted in decreased ni-
trogen retention, while MT did not significantly alter nitrogen
Carew and Hill (1967) studied the effect of DES on protein
utilization in chicks fed diets containing glucose or corn oil as
the major energy component. Nitrogen retention was markedly decreased
by DES in the high fat diet at restricted levels of energy intake,
but not on the glucose diet. The authors concluded that in chicks
the effect of DES on certain metabolic processes was influenced by
the form in which dietary energy was supplied.
Lassiter et al. (1956) studied the minimum protein intake for
pigs for maximum nitrogen retention. They also investigated the pre-
cision of 3, 5, and 7 day collection periods for estimating nitrogen
balance. With 23 kg pigs, nitrogen retention increased with increas-
ing protein levels up to 18 percent. With 68 kg pigs, protein levels
from 10 to 22 percent did appear to affect nitrogen balance, but the
difference was not significant. These workers also reported that
after a 10 day preliminary period, the 7 day collection period offered
only a slight advantage over the 3 day collection period with 23 kg
pigs and even less advantage with 68 kg pigs.
The anabolic effects of DES vary markedly with species, age,
sex, diet, and status of body protein stores, as shown by evidence
in work cited in this section.
The Mechanisms of Anabolic Action of
Androgens and Diethylstilbestrol
The means by which certain steroid hormones and diethylstilbes-
trol stimulate anabolism have been the subject of intense scrutiny
by researchers as long as the anabolic effect has been known. There
has been no clarification of the exact mechanism by which these sub-
stances stimulate protein anabolism.
Dorfman (1961), at a symposium on the mechanism of action of
steroids, proposed a working hypothesis for androgens which places
the mechanism of action of androgens at the level of regulation of
rate of biosynthesis of specific enzyme systems (protein synthesis).
The action of androgen is visualized as producing the necessary criti-
cal enzyme concentrations which result in growth of tissue. Androgen
may act as an inhibitor of catabolism or an inducer of anabolism in
Wilson (1962) studied protein synthesis in rat seminal vesicle
tissue as influenced by testosterone. Radioisotope 14C-labeled
amino acids were used to study protein biosynthesis rate in tissue
following testosterone administration. Protein synthesis was
doubled 12 hours after testosterone administration and reached a
maximum (5 to 6 fold) within 24 to 48 hours. There was evidence
that this enhancement of protein synthesis was independent of either
amino acid transport or synthesis, but was secondary to the accelera-
tion of a specific step in protein synthesis, the conversion of
soluble ribonucleic acid amino acid complexes to microsomal ribo-
Further work should serve to elucidate more clearly the exact
mechanisms involved in anabolic action of androgens.
Several theories concerning the mechanism of action of diethyl-
stilbestrol in stimulating nitrogen retention have been advanced by
various workers. The most promising hypothesis concerns the effect
of stilbestrol on growth hormone secretion. Struempler and Bur-
roughs (1955) reported that both DES and growth hormone increased
gains and nitrogen retention in lambs. When both substances were
administered together, however, no additive effect was observed.
This observation led them to conclude that DES may cause an increase
in secretion of growth hormone from the pituitary gland.
Davis, Garrigus, and Hinds (1970) studied the metabolic effects
of DES and growth hormone in lambs. They also observed very similar
responses to DES and growth hormone administration, and also concluded
that secretion of growth hormone might be increased by DES.
Generally, however, the mechanism of anabolic action of DES re-
mains unclear. Even less is known about this substance than is
known about anabolic steroids. It does appear that DES stimulates
nitrogen retention more markedly and more consistently in ruminants
than in nonruminants.
No direct evidence for an increase in secretion of growth hormone
caused by DES has been presented, although there are indications that
this may be the mechanism by which DES improves growth and nitrogen
These experiments were conducted to investigate the effects of
hormone supplementation (DES + MT at 2.2 mg each/kg of feed) and the
interrelationships with protein level (12 to 16%) and sex (barrow or
gilt) in swine. Treatment effects were measured by feedlot performance,
carcass parameters, and nitrogen balance studies.
General Experimental Methods
The experiments reported herein are on file in the Swine Nutri-
tion section of the Animal Science Department, Institute of Food and
Agricultural Science, University of Florida, Gainesville, Florida,
32601. Six trials were conducted between February 1967 and October
1969 and the series designated as Swine Experiment 178. Individual
trials were numbered as Experiments 178-A through F.
Animals used were Landrace x Duroc 2 way and (Landrace x Duroc)
x Hampshire 3 way cross-bred pigs. They were raised at the University
of Florida Swine Unit and were fed a typical practical fortified
corn-soybean meal ration from weaning to the time they were placed on
experiment. Sound management practices in raising the baby pigs were
followed to ensure healthy experimental animals. Male pigs were cas-
trated at approximately 7 to 10 days of age. All pigs had their ears
notched at birth for identification and were vaccinated against swine
erysipelas at approximately 6 weeks of age. The pigs in the first
two experiments (178-A and B) were vaccinated against hog cholera as
Allotment, Feeding, and Weighing
Outcome groups were chosen on the basis of sex, weight, and
litter, and these groups were randomly assigned to treatments.
Pigs in all feeding trials were fed ad libitum from self
feeders. Pigs in the metabolism trials were full-hand-fed twice
daily. Water was supplied ad libitum from automatic water fountains.
All pigs were fed in confinement on concrete or steel mesh floors.
All feed used was in a dry meal form. Hormone feeding was discontinued
for 72 hours prior to slaughter. Feed was weighed back every 2 or 4
weeks and a final weighback was taken at the termination of the feed-
ing trial. Compositions of the diets, level of hormone supplementation,
and compositions of the mineral and vitamin premixes are shown in
Tables I through 5.
Animals were weighed initially, and at I or 2 week intervals
thereafter until slaughter. A platform scale was used for weighing.
Slaughter Procedure and Carcass Evaluation
As live weight of the pigs reached 100 kg, they were slaughtered
at the University of Florida Meats Laboratory. Carcasses were dressed
packer style (head off) for study. All carcass weights and measure-
ments were taken after the carcasses had been chilled for 48 hours at
2 50 C. The length of carcass was measured from the anterior edge
of the aitch bone (pelvis) to the anterior edge of the first rib.
Average backfat thickness was calculated from measurements taken at
the first rib, last rib, and last lumbar vertebra. Loin eye area
was determined as an average of the left and right sides. The loins
were cut perpendicular to the vertebral column between the 10th and
Ilth rib to expose the longissimus dorsi. Tracings of the perimeter
of the loin eye were made, and their area determined by the use of
a compensating polar planimeter. The carcasses were broken down by
standard procedure and weight of wholesale cuts was determined. In
addition, the loin eye muscle was scored for marbling, color, and
firmness (Tables 6, 7, and 8). Blade loin roasts and loin chops were
wrapped for freezing and were frozen and stored at -15* C. Before
cooking, roasts and chops were thawed overnight at 10 C. Roasts were
cooked in covered Pyrex dishes in an oven preheated to 175 C. The
same cooking temperature was used for chops as for roasts. Chops were
cooked in Pyrex Petri dishes covered with watch glasses. Roasts were
cooked 60 to 80 minutes per kg to an internal temperature of 175* C;
chops were cooked for approximately 30 minutes. Aroma and flavor were
determined by a trained 6 member panel. Degree of boar odor and flavor
were the only palatibility factors considered. Table 9 shows the code
used for scoring samples.
Tissue Sampling and Preparation
Loin chops 2.5 cm thick taken between the 10th and 13 rib were
wrapped for freezing and frozen and stored at -15' C for subsequent
chemical analysis. To prepare the sample chop for analysis, a band
saw was used to isolate the longissimus dorsi while the chop was still
frozen. All external fat and bone were removed. The remaining frozen
longissimus dorsi section was quartered with the band saw, placed in
a coded plastic bag, and returned to the freezer for pulverizing.
Longissimus dorsi sections were pulverized in the freezer room at
-15* C by placing each sample individually in a commercial duty, rotary-
blade blender with a I liter stainless steel container, along with
200 g of dry ice (approximately twice the sample volume). The blender
was cooled to -150 C in the freezer prior to use. The cover was placed
on the blender, held in place firmly by hand, and the blender was
switched on to high speed. After approximately 60 seconds the blender
was switched off, the pulverized, frozen composite of meat and dry
ice was placed in a coded plastic bag, and the bag was closed loosely
with a rubber band.
The pulverized samples were stored in the freezer at -15' C for
at least 24 hours prior to weighing out aliquots for analysis. This
storage interval was necessary to allow time for all of the pulverized
dry ice to sublime, leaving only the pulverized frozen meat in the
sample bag. Sample aliquots of powdered meat were weighed while frozen
in a cool room (2' 4 C) as quickly as possible to prevent thawing.
Feed Sampling and Preparation
Feed samples were taken from each mixing batch and pooled at the
end of the feeding trial. A sample of this composite was retained
for chemical analysis. Following drying, the sample of feed was ground
in a Wiley mill with a 1 mm screen. The ground sample was stored in
a coded glass screw-top bottle for chemical analysis.
Feces Sampling and Preparation
In the metabolism trials (Experiments 178-E and F) total collection
of feces from each pig for each 24 hours of the 6 day collection period
was performed. The feces were put in coded plastic bags, weighed to
the nearest 0.1 g on a single pan balance, frozen, and stored at -15* C
for later analysis. Preparation for analysis was begun by thawing the
frozen feces. The entire amount of feces from each pig for each day
of the collection period was placed individually in a commercial duty
rotary-blade blender with a stainless steel container having a 4 liter
capacity. An amount of distilled water equal in weight to the original
weight of the feces sample was added, and the blender was switched on
to high speed. The resulting slurry was a completely homogeneous mix-
ture from which a truly representative sample aliquot could be taken
easily. Following drying, each sample was ground in a Wiley mill
with a 1 in screen and stored in a coded glass screw-cap bottle.
Urine Sampling and Preparation
In the metabolism trials (Experiments 178-E and F), total collec-
tion of urine from each pig for each 24 hours of the 6 day collection
period was performed. The total volume of the daily urinary output
was measured to the nearest 5 ml in a 2 liter graduated cylinder.
From the total daily urinary output of each pig, an aliquot of approx-
imately 250 ml was filtered through cheesecloth into a coded poly-
ethylene screw cap bottle to which 1.0 ml of concentrated hydrochloric
acid was added as a preservative. The pH was tested with pHydrion
paper to be sure it was in the range of 1.5 to 2.0. If it was not,
concentrated hydrochloric acid was further added, drop by drop, until
the desired pH was obtained. Samples were then frozen and stored
at -15* C.
All samples for analysis were weighed on a single pan analytical
balance to 4 decimal places. Aluminum foil weighing dishes were used
for all samples except those on which nitrogen was to be determined;
those samples were weighed on small squares of glassine paper and
folded quantitatively within the paper for analysis.
Moisture was determined on all feed, feces, and meat samples
taken during the course of the investigation. Feed and feces samples
were dried prior to grinding as previously described and the moisture
was determined at this initial drying. The general procedure for
determination of moisture was similar for feed, feces, and meat.
Duplicate samples of the material being analyzed were quantitatively
weighed into numbered aluminum foil weighing dishes of known weight
and placed in a 1000 C drying oven. Feed samples were dried for 24
hours, but feces and meat samples required 48 to 72 hours before
a complete removal of water was accomplished.
The dried samples were cooled to room temperature in desiccators
and weighed to determine the loss of moisture. In the case of feces
samples it was necessary to correct for the water added during homo-
genization. Sample size for feed was approximately 50 g. Between
100 and 200 g of feces slurry was used for the moisture determination
on the feces samples. Meat sample size was between 5 and 15 g.'. Dried
samples of feed and feces were ground and stored as previously de- -
scribed. Meat samples remained in their small (6 x 1.5 cm) aluminum
foil weighing dishes and were stored in desiccators for later analysis.
Ether Extract Determination
The ether extract determination was performed on the same meat
samples used in the moisture determination. The small foil pans con-
taining the dried meat samples were carefully rolled up to quantita-
tively enclose the samples; then the rolled pans with samples were
placed in numbered Whatman cellulose extraction thimbles (25 x 80 mm).
The weight of each thimble, pan, and sample was quantitatively deter-
mined. Samples were then extracted for 24 hours with petroleum ether
on a Goldfisch apparatus. Following extraction, the samples were
dried and the weight of the thimble, pan, and extracted sample was
quantitatively determined. The difference was reported as fat.
A modified Kjeldahl process (W.V. Stradtmann, personal communi-
cation) was used for nitrogen determination. Feed, feces, and meat
samples for this determination were quantitatively weighed onto small
squares of glassine paper (approximately 8 x 10 cm).
The papers were then carefully folded to quantitatively enclose
the samples, and the papers with samples were put into coded 100 m!
Pyrex semi-micro digestion flasks. Sample size was approximately
0.4 g for feed and feces and 1.0 to 1.5 g for meat samples. Urine
samples were pipetted into the digestion flasks. Sample volume for
urine was 4.0 or 5.0 ml. After the sample was in the digestion flask,
5 or 6 glass beads were added to prevent bumping during digestion.
Concentrated sulfuric acid (5 ml) was used to char the samples for
The flasks containing samples, beads, and acid were then boiled
over a free flame until sulfur trioxide fumes appeared in the necks
of the flasks, and acid was refluxing down the necks and sides of the
flasks. The flasks were then removed from heat and allowed to cool
in the air for about 1 minute. Superoxol (30% hydrogen peroxide) was
added drop by drop to the hot acid digests until the blackish-brown
mixture turned clear, indicating complete oxidation of organic matter.
The digested sample was then cooled in the air to ambient temperature
and quantitatively transferred from the semi-micro digestion flasks
to 500 ml macro distillation flasks. Three washes with distilled water
were used to accomplish the transfer. The sample was then treated as
in the normal Kjeldahl process (A.O.A.C., 1960). Mossy zinc and
concentrated sodium hydroxide were added and the alkaline mixture
was distilled to drive off ammonia into receiving flasks containing
50.00 ml of dilute sulfuric acid of known normality. Following dis-
tillation, the acid remaining in the receiving flasks was titrated
to the methyl red end point with 0.1000 normal sodium hydroxide.
The percent nitrogen in the samples was then calculated, and in the
case of feed samples and meat samples it was multiplied by a factor
of 6.25 to convert to percent protein. A blank and a standard
(ammonium sulfate) determination were run with every group of 24
Determination of 17-ketosteroids in Urine
A determination of the urinary 17-ketosteroids (Sigma Tentative
Technical Bulletin No. 17-KS) was performed on composite samples of
urine from each pig in the metabolism trials (Experiments 178-E and
F). In order to compensate for variation in daily urine output vol-
ume, samples from each pig for each day of the collection period were
pooled in a ratio comparable to the daily urine volume. Duplicate
determinations of 17-ketosteroids were run on the composite samples
and the results were reported as average excretion of 17-ketosteroids
in mg per day. The Zimmerman reaction (Dorfman and Shipley, 1956)
was used to determine concentration of 17-ketosteroids in urine. Fil-
tered urine samples of 5.0 ml were acid hydrolyzed (to free conjugated
steroids) in a boiling water bath for 15 minutes, cooled, and trans-
ferred to separatory funnels. The hydrolyzed samples were then
extracted with approximately 20 ml of ethyl ether and washed with
2.0 normal sodium hydroxide. The washed extracts were filtered into
large test tubes, evaporated to dryness, and redissolved in 0.20 ml of
absolute methanol. The alcoholic solutions were incubated at room
temperature for 20 minutes following the addition of 0.20 ml of
meta-dinitro-benzene and 0.20 ml of 8.0 normal potassium hydroxide
to each sample. Following incubation, 1.0 ml of distilled water and
5.0 ml of methylene chloride were added to each sample and the solu-
tions were shaken to mix thoroughly. Approximately 5 minutes after
shaking, the top aqueous layer was aspirated off the solutions and
1.50 ml of absolute methanol was added to allow development of the
purplish color characteristic of the steroid-dinitrobenzene complex.
Solutions were transferred to cuvettes and the percent transmittance
was read in a colorimeter with the blank solution as a reference for
100 percent transmittance. Maximum absorbency occurred at a wavelength
of 540 mu.
A standard solution was also carried through the extraction pro-
cess with every 8 determinations. The percent transmittance values
of a series of solutions of known concentration were plotted on semi-
logarithmic graph paper to produce a linear standard curve from which
the concentration of 17-ketosteroids in unknown solutions could be
determined directly. The concentration of 17-ketosteroids in mg per
liter was multiplied by the mean daily urine output in liters to give
the value in mg of 17-ketosteroids excreted per day.
All data collected from the experiments were analyzed statis-
tically using the methods of Steel and Torrie (1960). Analysis
of variance was used to determine significant effects. Wherever
significant main effects were not complicated by interaction, pooled
means for the main effects are presented in the figures. Any refer-
ence to statistical significance regarding main effects refers to
the probability level of 5 percent or less.
Wherever significant 3 factor interaction occurred, means for
the treatments were tested for significant differences by Tukey's w
procedure using the upper 10 percentage points of the studentized
range. Wherever a significant 2 factor interaction occurred in the
3 factor experiments (178-A and B) data were summed and averaged
across the independent factor. The 2 factor simple effects were then
tested for significant difference by Tukey's w procedure using the
upper 10 percentage points of the studentized range. Treatment means
in the 2 factor experiment (178-D) were tested in a similar manner
where interaction occurred.
Since Tukey's procedure is so conservative, Steel and Torrie
(1960) suggest that the experiment-wise error rate can be relaxed to
10 percent without danger of committing a large number of Type I
errors (declaring observed differences falsely significant). Because
of this, the 10 percent level was used to test for significant differ-
ences in these experiments where interaction occurred.
The standard deviation of a treatment mean (s-) was estimated by
/error mean square
/ no. of observations in mean for calculating w. The value of
S= qp,n2 s, where a = 0.10, p = number of means being compared,
and n2 = error degrees of freedom. The q values were obtained from
tables of the upper percentage points of the studentized range
A group of 72 carefully selected crossbred pigs was placed on
experiment at an initial average weight of 45 kg. This first trial
was begun on February 16, 1967. Pigs were group fed in concrete con-
finement from a self feeder to an average weight of 95.3 kg, at
which time the entire group was slaughtered for carcass study. The
termination of the feeding trial was on April 22, 1967, 66 days after
the starting date. The design of the experiment was a 2 x 2 x 2
factorial design (Table 10) which involved sex (barrow and gilt),
protein level (16 and 12% protein), and hormone supplementation
(basal and DES + MT, each at 2.2 mg/kg of feed). Compositions of
the rations used are shown in Table 1.
The summaries, analysis of variance plans, and observed mean
squares for Experiment 178-A are presented in Tables 11 through 16
and Figures 1 through 12. Table 13 presents an overall summary of
all the responses measured in Experiment 178-A. Significant mean
squares are presented in Tables 14 through 16. Figures illustrate
all significant interactions and main effects.
Table 11 presents a summary of the feedlot performance of the
4 treatment groups. Table 12 shows the combined protein and hormone
treatment means and the appropriate standard deviations of treatment
means. The t test did not reveal any significant differcnccs in feed-
lot performance due to hormone or sex. Treatment means of total
gain from initial to market are shown in Table 13. There were no
significant differences in total gain between any treatments.
Carcass responses are shown'in Table 13. There was a signi-
ficant protein x hormone x sex interaction which affected dressing
percentage. This interaction is illustrated in Figure 1. Gilts
showed an increased dressing percentage on the basal ration as protein
was increased, and a decreased dressing percentage was noted when
protein was increased on the hormone supplemented ration. The reverse
effect was seen in barrows. Hormone increased dressing percentage
with increasing protein. Increasing protein on the basal ration did
not affect barrow dressing percentage. The effect of hormone supple-
mentation in reducing dressing percentage was significant only at
the 16 percent protein level in gilts and at the 12 percent protein
level in barrows. Due to this interaction, no inferences can be made
about the main effects on dressing percent.
There were two significant interactions which influenced percent
lean primal cut yield. The 2 factor hormone x sex interaction was
disregarded since there was also a significant 3 factor interaction.
The 3 factor protein x hormone x sex interaction illustrated in
Figure 2 shows that gilts responded nearly the same on the basal and
hormone rations to increased protein. There was an increased lean pri-
mal cut yield in gilts fed either diet (basal or DES + MT) when protein
was increased. Barrows showed increased lean primal cut yield in
response to hormone supplementation at both protein levels. Barrows
fed the 16 percent dict had a higher lean cut yield Lian those fed
the 12 percent protein regardless of hormone level. None of these
differences were significant (Table 13).
Percent ham was not affected by any factor except sex (Figure 3).
Gilts had significantly larger hams than barrows.
Percent loin was influenced by a significant 2 factor interaction.
This hormone x sex interaction is shown in Figure 4. Percent loin was
slightly decreased in gilts by hormone, but barrows showed a signifi-
cant increase in yield of loin in response to DES + MT. In addition,
gilts fed the basal diet yielded significantly higher percentages of
loin than basal barrows.
Percent yield of picnic shoulder was influenced by both hormone
and protein. There was a significant increase in percent picnic
shoulder in response to increased protein (Figure 5) and to hormone
supplementation (Figure 6).
Percent Boston butt was significantly increased by hormone
supplementation.(Figure 7). In addition, there was a significant
protein x sex interaction influence on yield of Boston butt. Barrows
showed a slight decrease in yield of Boston butt with increased pro-
tein, but gilts showed a moderate increase. Although this inter-
action was significant, none of the differences between means were
significant (Figure 8).
Backfat thickness was decreased significantly by both increasing
protein and DES + MT (Figures 9 and 10). No interactions were
observed to influence backfat thickness in this trial.
Loin eye area was not significantly affected by any of the treat-
ments in this experiment.
No significant differences in carccss length due to trcatmIICnt
Loin eye marbling score was significantly reduced by increased
protein (Figure 11).
No differences due to treatment were observed in loin eye color
score or firmness score.
Loin roast aroma and flavor scores for boar odor incidence were
significantly increased by DES + MT in this trial. A graphic presen-
tation of this difference is shown in Figure 12.
Experiment 178-8 was the second trial performed in the series,
and was designed in 2 parts. The first phase consisted of a completely
random design (Table 17) with sex of the pigs (barrow or gilt) as
the treatment factor. A carefully chosen group of 60 young crossbred
pigs with each sex represented equally was placed on experiment on
May 15, 1967. The average initial weight was 9.8 kg. The pigs were
segregated by sex and group fed on a 16 percent protein ration in
confinement on concrete to an average weight of 56.3 kg. The first
phase ended on July 25, 1967. The feedlot performance data collected
were analyzed to determine if there was any performance difference
In early life due to sex.
The second phase of the experiment was a 9 x 2 Y 2 factorial
design similar to Experiment 178-A. This trial was designed to further
investigate the effects of sex, protein level and hormone supplemen-
tation on growing-finishing pigs. The design of the experiment is
shown in Table 18. In this experiment it was decided to use a lower
level of protein (14%) than the 16 percent ration used in the first
trial, to see if a response to protein still occurred, and to see if
response to hormone remained the same at the lower level of protein.
Pigs in this trial were individually fed from self feeders in concrete
confinement pens. Compositions of the diets used are shown in Table
i. The 48 pigs used in this second phase were selected from the 60
pigs used in the first phase on a sex, weight, and littermate basis.
Starting date for the factorial trial was July 25, 1967. All pigs
were slaughtered (for carcass study) on an individual basis as ter-
minal weight reached approximately 100 kg.
The summaries of treatment means and analysis of variance plans
for Experiment 178-8 are shown in Tables 19 through 24 and Figures
1l through 22.
A summ-nary of the feedlot performance during the growing phase is
shown in Table 19. No significant differences were observed in per-
formance during early life between barrows and gilts fed a similar
16 percent protein ration (Table 20).
Average daily gain was significantly greater for barrows than
for gilts during the finishing phase (Figure 13). There was a signi-
ficant interaction of sex with DES + MT which influenced feed intake.
Barrows fed DES + MT ate significantly less feed during the finishing
phase than did barrows consuming the basal ration. Hormone supplemen-
tation did not affect feed intake in gilts (Figure 14). In addition,
Figure 14 shows that barrows fed the basal ration ate significantly
more feed than gilts fed either the basal or the hormone diet. Feed
efficiency was significantly improved by DES + MT in this trial
None of the main effects had a significant influence on dressing
percentage in this experiment, but there was a significant protein x
sex interaction effect (Figure 16). Increased protein resulted in
increased dressing percentage in barrows; this response was signifi-
cant in gilts.
There was a favorable effect of DES + MT on percent yield of lean
primal cuts. There was a significant interaction of sex x hormone
which is shown in Figure 17. This interaction manifested itself in a
differential response to hormone supplementation by sex. Gilts showed
only a slight increase in percent lean primal cuts, while barrows
showed a significant increase.
There were no significant differences observed In percent ham
In this trial.
There was a significant interaction of hormone x sex affecting
percent loin. Loin yield in gilts was not materially affected by
DES + MT, but barrows showed a significant increase in this cut due
to hormone supplementation (Figure 18).
Picnic shoulder and Boston butt percentage yield were unaffected
in this trial by any treatment.
Backfat thickness was significantly reduced in barrows by DES + MT
in this experiment. There were 2 significant interactions influencing
backfat thickness. The effects of both protein x hormone and hormone x
sex interactions are presented in Figure 19. The protein x hormone
interaction shows that average backfat thickness was not materially
affected by DES + MT on the high protein diet, but was significantly
reduced on the low protein diet. The hormone x sex interaction shows
that backfat thickness was not reduced in gilts fed DES + MT, but
was decreased to a significant extent in barrows.
Hormone x sex interaction significantly influenced loin eye area
in this experiment, but none of the treatment means differed signifi-
Carcass length was significantly increased by DES + MT in gilts
fed 12 percent protein in this trial. There was a significant 3 factor
interaction which influenced carcass length (Figure 20). Gilts fed
the basal ration showed an increase in carcass length as protein was
increased from 12 to 14 percent, but gilts fed the ration containing
DES + MT showed decreased length with increased protein. Thereverse
effect was true for barrows. DES + MT increased length of barrows
with increasing protein; barrows fed the basal ration showed a decreased
length as protein was increased. None of these effects were signi-
ficant, with the exception of the difference between gilts on the
basal and hormone rations at the 12 percent protein level.
Loin eye marbling score was not affected by any treatment in
Loin eye color score was not signnficant!y different between any
of the treatment groups in this trial.
Loin eye firmness score was significantly affected by sex. Gilts
had significantly firmer muscle (10th rib 1. dorsi) than barrows
Loin roast aroma and flavor scores for incidence of boar odor
and flavor were significantly increased by DES + MT in this experi-
ment (Figure 22).
The third trial in the series was designated as Experiment 178-C.
This trial was designed to examine the effects of DES + MT alone,
without protein or sex considerations. The experiment was a completely
random design (Table 25) utilizing 24 barrows individually fed in
concrete confinement from self feeders. The ration used (Table 1)
was a 14 percent protein corn-soybean meal diet fed with and without
2.2 mg of DES + MT per kg of feed. Pigs for this experiment were
randomly assigned to treatment from a uniform group. The trial com-
menced on January 23, 1969. Pigs averaged 45 kg initially and were
slaughtered on an individual basis for carcass study as weight reached
100 kg. There were 2 pigs in the trial, one assigned to each treat-
ment, with identical ear notch numbers; the identity of these two
animals was lost at slaughter. Therefore, the carcass data are all
based on the remaining 11 pigs in each treatment group.
Long ssimus dorsi samples from the 10th to 13th rib area were
analyzed for moisture, fat, and protein content in this trial.
The treatment means for Experiment 178-C are summarized in Table
26. Analysis of variance tables for this experiment are given in
Tables 27 through 31.
Out of 22 responses measured in this trial, only 3 showed any
Feedlot performance did not differ significantly between treat-
ments, but there was a trend toward decreased feed intake and improved
efficiency due to DES + MT.
None of the carcass objective measurements differed significantly
in this experiment, although there was a trend toward increased lean-
ness due to DES + MT. This was evidenced by slight increases in
carcass length and yield of lean cuts, and slight decreases in dressing
percent, backfat thickness and loin eye marbling score. Of all the
carcass leanness parameters, backfat thickness was most affected by
hormone supplementation, but even so, the difference was not signifi-
In this trial the only carcass subjective measurement which was
significantly affected by DES + MT was pork chop aroma score. There
was a significantly higher incidence of boar odor in chops from pigs
treated with DES + MT. None of the other carcass subjective measure-
ments, including chop flavor score, roast aroma score, and roast
flavor score, were significantly different.
Analysis of longissimus dorsi samples revealed a significantly
luwer percenLdge uo dry matter (higher % moisture) in pigs fed DES +
The percent protein in longissimus dorsi was significantly greater
for pigs fed DES + MT. Protein was expressed on a dry matter basis.
There was no significant difference in percent fat in longissimus
dorsi, although there was a trend toward decreased fat due to DES +
Experiment 178-D was the last in a series of 4 feeding trials.
In this trial, the design was a 2 x 2 factorial (Table 32) involving
sex and hormone supplementation. The protein level was fixed at
14 percent of the diet (Table 1). The crossbred pigs used in this
experiment were selected from outcome groups based on sex, weight,
and littermate, and were randomly assigned to treatments. The pigs
were fed in individual concrete confinement pens from self-feeders.
The average initial weight was 54.5 kg. Pigs were slaughtered on an
Individual basis for carcass study as they reached 100 kg. The trial
commenced on May 19, 1969. On this trial, one barrow died midway
through the experiment. Death was attributed to generalized edema
due to heat prostration. One pig carcass was condemned for a condition
of granuloma in the muscle, apparently unrelated to treatment. Be-
cause the orthogonality of the factorial design was destroyed by loss
of these data, computer analysis using a complete and a reduced model
was necessary in order to partition the sums of squares. Therefore,
only abbreviated analysis of variance tables are shown, and sums of
squares generated from these tables are not additive.
The summary of treatment means is shown in Table 33, and abbre-
viated analysis of variance tables are presented in Tables 34 through
37 and Figures 23 through 38 illustrate significant effects.
The interaction of hormone and sex influenced daily gain signi-
ficantly. This interaction is graphed in Figure 23, which shows
that daily gain in gilts was not materially affected by DES + MT,
but was significantly reduced in barrows by the hormone. Barrows fed
the basal diet gained significantly more than did gilts fed the basal
Average daily feed intake was significantly greater in barrows
than in gilts (Figure 24). Hormone supplementation also influenced
daily feed intake significantly. Pigs fed DES + MT consumed signifi-
cantly less feed than those fed the basal diet (Figure 25).
Feed conversion efficiency was favorably affected by DES + MT.
Pigs consuming the hormone supplemented feed had a significantly
lower feed conversion ratio than pigs fed the basal diet. This differ-
ence is shown in Figure 26.
Dressing percentage was not affected by any treatment in this
Hormone supplementation markedly increased the percent yield
of lean primal cuts in this experiment (Figure 27).
There were no significant main effects seen in percent ham yield,
but the hormone x sex interaction was significant. This interaction
is illustrated in Figure 28. The graph shows that DES + MT decreased
yield of ham slightly in gilts, but increased it significantly in
barrows. Gilts fed the basal ration had significantly larger hams
than barrows fed the basal ration.
Percent yield of loin was not significantly affected by any
Percent yield of picnic shoulder was increased by DES + MT. This
effect was significant (Figure 29).
There was also a positive significant response to DES + MT
manifested in percent yield of Boston butt (Figure 30).
Backfat thickness was significantly reduced by supplementation
with DES + MT (Figure 31).
Loin eye area was not affected by any treatment in this trial,
nor was carcass length. Liver weight was also measured in this trial,
but no significant differences due to any treatment were observed.
Loin eye marbling score, loin eye color score, and loin eye firmness
score were all unaffected by any treatment.
Loin tenderness score was significantly different between sexes
(Figure 32). The meat from barrows required less shear force to part
the fibers than did that from gilts.
In this trial, the boar odor and flavor incidence scores for
pork chop aroma and flavor and loin roast aroma and flavor were sig-
nificantly increased by DES + MT (Figures 33 and 34).
Moisture, fat, and protein were determined on longissimus dorsi
samples taken from the 10th to 13th rib area. The percent dry matter
i. the melt '.s not significantly different bet...'cen tre.tm.nts.
Percent protein in longissimus dorsi (expressed on a dry matter
basis) was significantly lower in barrows than in gilts, and was
significantly decreased by hormone supplementation (Figures 35 and 36).
Percent fat in longissimus dorsi (expressed on a dry matter
basis) was significantly affected by sex and DES + MT. In this trial,
gilts showed significantly less fat in the lean tissue than barrows
(Figure 37). Supplementation with DES + MT significantly increased
the percent fat in longissimus dorsi over that found in pigs fed the
basal ration (Figure 38).
This trial concluded the series of feedlot performance and
carcass study experiments. Table 44 presents a summary of all the
significant performance and carcass responses observed in the 4 trials.
Experiments 178-E and F
Experiments 178-E and F were the last two experiments performed
in the 178 series. Both of these trials were metabolism studies.
Barrows were housed in metabolism crates constructed so as to permit
total collection of all excreta separately. The crates were equipped
with automatic water fountains, and with fans for cooling. The floors
were of expanded steel mesh. Barrows were full-hand-fed twice daily
and a record of daily feed intake was made. Barrows were weighed,
placed in the crates, and fed the experimental diets for a period
of acclimatization to the regime. The pretrial period was 9 days in
the first metabolism trial and !! days in the second one. Collection
of total feces and urine excreted was made as previously described
for a period of 6 days in both trials. Barrows were weighed again
at the termination of the feeding period.
The design of the experiments is shown in Table 38. In the
first metabolism trial (conducted from May 29 to June 12, 1969),
crossbred barrows averaging 58 kg initially were used; terminal
average weight was 65.7 kg. In the second metabolism trial (conducted
from July 28 to August 14, 1969), similar barrows were used. Average
initial weight was 57.1 kg, and average terminal weight was 67.8 kg.
Each trial consisted of 8 barrows; the blocks used in the design
were littermate pairs, and four barrows were assigned to each treat-
ment. The basal (14% protein) diet was fed with and without 2.2 mg
of DES + MT per kg of feed, as shown in Table 1.
Criteria examined in both trials were daily feed intake, total
gain, daily nitrogen retention (g N/kg feed consumed), apparent di-
gestibility of dry matter and nitrogen, and excretion of 17-keto-
steroids in urine.
The treatment means for both trials are shown in Table 39, and
analysis of variance plans are presented in Tables 40 and 41 for
for Experiment 178-E and Tables 42 and 43 for Experiment 178-F.
No significant difference due to DES + MT was observed in daily
feed intake, although a slight decrease in feed intake in the first
metabolism trial and a more marked decrease in the second occurred
in pigs fed the hormone supplement.
Total gain was veiy slighLiy deuresede in pigs Fed DES + MT in
Experiment 178-E, but was moderately increased in hormone supple-
mented pigs in Experiment 178-F. Neither difference was significant,
Daily nitrogen retention, expressed as g of nitrogen retained
per kg of feed consumed, did not differ significantly due to treat-
ment in either trial. Pigs fed DES + MT showed a moderate decrease
in nitrogen retention in the first metabolism trial, but showed only
a slight decrease in the second trial; neither difference was great
enough to be significant.
Apparent digestibility of dry matter and nitrogen was similar
for both treatment groups in both trials. Digestibility did not appear
to vary between trials, either.
In the first metabolism trial, excretion of 17-ketosteroids in
urine was significantly different due to treatment. Pigs fed DES +
MT had a higher daily excretion of 17-ketosteroids in urine than pigs
fed the basal ration. In the second trial opposite results were ob-
served. Pigs fed the hormone supplement in this experiment showed a
lower daily excretion of 17-ketosteroids in urine than did pigs fed
the basal diet, but this difference was not significant.
The Effects of Hormone, Protein, and Sex on the
Fprdlot Pprfnrminrp nf Grrwin n-Finiching Swin"
Several recent studies have been reported which indicate that
OES + MT affects the performance of swine in the feedlot.
Wallace et a!. (1967) reported a significant decrease in both
average daily gain and average daily feed intake due to feeding DES +
MT at 2.2 my each per kg of diet.
Baker et al. (1967) reported that DES + MT decreased average
daily gain in barrows, but not in gilts. They observed also that feed
efficiency response to DES + MT was obtained only at higher levels
Doornenbal and Frankenham (1969) reported a non-significant
increase in average daily gain for gilts and barrows fed a practical
high protein ration containing 2.2 mg each of DES + MT per kg of feed,
but they reported that feed efficiency was not altered by treatment.
Average Daily Gain
In this series of experiments, rate of gain was affected signif-
icantly by hormone in only 1 out of 4 trials (Table 44). Hormone
treatment decreased rate of gain only in barrows in this particular
case, since there was a significant interaction of hormone x sex.
Sex affected rate of gain in two trials (Table 44). Barrows gained
significantly faster than gilts. No effect on rate of gain due to
protein level was observed in any trial.
Barrows responded significantly more to DES + MT than gilts.
This difference was manifested in a marked decrease in rate of gain
for hormone supplemented barrows, but essentially no change :a'
observed in gilts fed the hormone. This interaction of DES + MT with
other factors (especially sex and protein level) may be one reason
that some of the responses to DES + MT in some trials have been so
variable. This observation on gain response to DES + MT is in general
agreement with other work reported in papers mentioned in the litera-
ture review. Gain response to this combination of hormones has been
erratic at best, and it may be that the response varies with experi-
Average Daily Feed Intake
Feed intake is one of the most variable parameters in animal
research. Daily feed consumption can be affected by a variety of
factors, including hormone supplementation, sex, and protein level.
In this experiment there was a significant reduction in feed intake
attributed to DES + MT in the second and fourth feeding trials (Table
44).. In the other trials there was a marked trend toward reduced
feed intake due to hormone, but the effect was not significant. There
was a significant hormone x sex interaction in Experiment 178-B.
This pattern has been noted by other workers (Wallace et al., 1967;
Beacom, 1963) who reported that feed intake in gilts was unaffected by
hormone supplementation, but was markedly decreased in barrows when
DES + MT was added to the ration. In this experiment sex also in-
fluenced daily feed intake significantly in the last feeding trial
(Table 44). Barrows consumed significantly more than gilts in
The observed trend toward decreased feed intake was rather con-
sistent in this study, and has also been reported by numerous other
workers. Either DES or MT fed alone is capable of eliciting the re-
sponse (Dinusson et al., 1951). The feed intake reduction is most
probably one of the factors contributing to reduced rate of growth
and increased feed efficiency reported in many of the trials involving
Feed Conversion Efficiency
The feed conversion efficiency ratio (feed/gain) was significantly
improved by DES + MT in the same 2 trials which showed a significant
decrease in feed intake caused by the hormone. Neither sex nor pro-
tein significantly influenced feed efficiency in any trial conducted
in this experiment.
It is probable that the decreased feed intake due to hormone
was responsible for this increased efficiency observed in the same
experiments. Dinusson et al. (1951) and Heitman and Clegg (1957)
reported improved efficiency due to supplementation with DES.
Wallace et al. (1967) reported that increased feed conversion
efficiency due to DES + MT was manifested most at higher protein levels.
This Is in agreement with the work of Baker et al. (1967), who re-
ported similar findings.
Opposite results were observed in this study. There were 2 trials
in which protein level varied (Experiments 178-A and B). No signifi-
cant differences in feed efficiency were observed in Experiment 178-A,
but in Experiment 178-B there was a more marked improvement in
efficiency due to DES + MT in pigs fed the low protein diet than in
those fed the high protein diet.
In Experiment 178-D, efficiency was improved more by DES + MT
in gilts than in barrows.
The Effects of Hormone, Protein, and Sex on the
Carcass Characteristics of Swine
Dressing percentage was affected by hormone in only the first
trial of this series. Beacom (1963) reported no change in dressing
percentage due to DES or a combination of estradiol and testosterone.
Other workers have obtained similar results.
There was a significant 3 factor interaction (protein x hormone x
sex) observed in the first trial, which influenced dressing percent.
When this interaction was graphed (Figure 1) it was evident that bar-
rows and gilts responded in an opposite manner to hormone supplemen-
tation and protein level. Differences in carcass leanness in barrows
and gilts fed different protein levels are well documented. It may
have been this effect which was responsible for the 3 factor inter-
action. Due to this 3 factor interaction, it was impossible to make
inferences concerning any of the main effects on dressing percent.
Percent Lean Primal Cuts
Percent lean primal cuts are a good index of overall carcass
leanness. Lean primal cuts were increased significantly due to DES +
MT in 3 out of 4 trials (Table 44) in this study. Increased protein
level was also responsible for an increase in percent lean cuts in
the first trial. This increase in percent lean cuts due to DES + MT
was probably an additive effect accumulated in increments in each of
the 4 lean cuts. Percent ham was not changed by DES + MT in any
trial, but was significantly greater in gilts than in barrows in
Experiment 178-A. In addition, there was a significant hormone x sex
interaction which affected percent ham in Experiment 178-D. Gilts
did not respond to DES + MT, while barrows showed a significant in-
crease in percent ham due to the hormone. There was a significant
hormone x sex interaction influencing percent loin in the first two
trials (Figures 4 and 18). In both cases, gilts showed a very slight
negative response in percent loin to. the hormone supplement, while
barrows responded with a marked and significant increase in loin yield.
Percent picnic shoulder was significantly increased by DES + MT in
2 trials, as was percent Boston Butt.
When the cumulative effects of these increases are summed together
into percent lean primal cuts, the result is a consistent increase of
lean cuts in the range of about 2 percent. There were 2 significant
hormone x sex interactions which showed a differential response in per-
cent lean cuts due to DES + MT in barrows and gilts (Figures 2 and 17).
Barrows responded more markedly than gilts to hormone supplementation
influence on percent lean cuts.
In general, this response in lean cuts is a good indication that
there is a significant improvement in carcass leanness due to DES +
MT. This observation is in agreement with the results reported by
Wallace et al. (1967), Baker et al. (1967), Beacom (1963), and Door-
nenbal and Frankenham (1969). Hale and Johnson (1970) also reported
Sncrsin Ican cuts du- to hormone zupplementation.
Workers cited in the preceding section and in the literature re-
view have reported that, accompanying the increased yield of primal
cuts usually stimulated by DES + MT, there is nearly always a simul-
taneous decrease in backfat thickness. Results obtained in this
investigation corroborate these findings. Backfat thickness was sig-
nificantly reduced by DES + MT in 3 out of 4 trials. Protein level
also tended to affect backfat in the first trial. Increased protein
level decreased backfat significantly. In the second trial, both
protein and sex interactions with hormone affected backfat thickness
response (Figure 19). From the graphs of these interactions it is
apparent that DES + MT reduced backfat in barrows and in pigs fed the
low level of protein.
These results are logical, since gilts are usually leaner than
barrows to start with, and pigs fed high levels of protein are
leaner than those fed low levels of protein; therefore, the gilts
and high protein fed pigs would respond less in backfat thickness
reduction when DES + MT was fed.
Loin Eye Area
Loin eye area was not affected by DES + MT in any of the trials.
This is in agreement with the work of Wallace et al. (1967). Baker
et al. (1967) reported an increase in loin eye area due to DES + MT
only at superadequate levels of protein.
Carcass length was affected by hormone in only one trial. Gilts
fed DES + MT at the 12 percent protein level had significantly longer
carcasses than those fed the 12 percent protein basal ration. No
other inferences concerning main effects on carcass length are mean-
ingful due to the significant 3 factor interaction observed. There
was a non-significant trend toward increased length due to DES + MT
in the other trials. Baker et al. (1967) also reported an increased
length of carcass due to DES + MT.
Carcass Subjective Measurements
None of the trials showed any significant response to DES + MT
in loin eye marbling score, loin eye color score, loin eye firmness
score, or loin tenderness score. These responses were similar in all
4 trials. Loin meat aroma and flavor scores for incidence of boar
odor were significantly increased in all 4 trials. There appeared to
be a definite increase in the incidence of boar odor and flavor in
the meat of pigs fed DES + MT. This boar odor increase was strongly
manifested in the first 2 trials, and'was seen to a lesser extent in
the last 2 trials. In the first 2 trials, a number of carcasses were
condemned for boar odor incidence, but in the last 2 trials, eating
quality of the meat of most pigs was judged acceptable even though
a slight boar odor in meat of treated pigs was detectable by a trained
These results are in agreement with those reported in numerous
papers cited in the literature review. 'WallacL etL ol. (15U7) found
a very strong boar odor in meat of pigs fed DES + MT. The odor prob-
lem seems to be complex, and is affected by other factors than hormone
supplementation (Martin, 1968). There seems to be no doubt, however,
that methyltestosterone is the hormone responsible for stimulation of
the production of this odor and flavor.
Chemical Composition of Loin
In the last 2 trials, the chemical composition of samples of
lean longissimus dorsi was determined. Percent dry matter in the loin
was significantly less for pigs fed DES + MT in Experiment 178-C.
Percent protein in loin was also significantly increased by DES + MT
in this experiment. Fat content was also reduced non-significantly
in hormone fed pigs in this trial. Results differed markedly in the
next trial. There was no significant difference observed between
treatment groups in percent dry matter. Percent protein in the loin
was significantly decreased by DES + MT, and percent fat was signifi-
cantly increased by hormone. This same trend was apparent in differ-
ences between barrows and gilts, the loins of barrows being signifi-
cantly fatter and having less protein than those from gilts. The
difference in these responses between the two trials is difficult to
In Experiment 178-C, loin percent dry matter and protein and
pork chop aroma score were the only responses observed to be signi-
ficantly different due to treatment. None of the carcass leanness
parameters were significantly different, yet loins of treated pigs
were significantly leaner as evidenced by chemical analysis. On the
other hand, in Experiment 178-D, the major carcass leanness indices
(percent lean primal cuts and backfat thickness) were significantly
improved by hormone supplementation, yet loin meat from treated pigs
contained significantly more fat and less protein than meat from con-
trol pigs. These results are in conflict with those reported by
Doornenbal and Frankenham (1969), although the results of Experiment
178-C agree with their findings. Plimpton (1966) reported that 70
kg boars implanted with 96 mg of DES had (at slaughter weight) a
greater percentage of moisture and a lower percentage of fat in the
longissimus dorsi than did control boars. The pigs in Experiment
178-D which received DES + NT had every indication of being leaner,
meatier animals than the control group. Loin eye marbling score was
Increased non-significantly by DES + MT in this trial, and this in-
crease in marbling is probably the cause of the increased fat content
and decreased protein content observed in longissimus dorsi samples of
treated pigs. DES + MT may decrease depot fat to a greater extent
than intramuscular fat.
The Effects of DES + MT on the
Nitrogen Retention of Growing-Finishinq Swine
There is some evidence (D. H. Baker, unpublished data) that DES
+ MT stimulates increased nitrogen retention in swine. Baker studied
the nitrogen retention patterns of 6 barrows in a cross-over design
and found that in every case feeding DES + MT resulted in an increased
nitrogen retention in these barrows. An increase in protein anabolism
due to DES alone and MT alone is well documented in other species
especially in ruminants in the case of DES. Certainly one might ex-
pect to find an increase in nitrogen retention due to therapy with
known potent anabolic drugs.
Results of the two metabolism trials performed in this investi-
gation conflict with this. There was a slight but non-significant
decrease in nitrogen retention of barrows fed DES + MT in two trials.
Other parameters were also not significantly different. These results
are opposite those of Baker's unpublished data. Several explanations
of this difference come to mind. The pigs in this trial were full-
hand-fed a 14 percent protein diet twice daily, while Baker used 16
percent protein, and restricted daily feed intake to 1.8 kg per day.
In Experiment 178-E the pigs consumed less feed than did Baker's pigs,
but the feed intake of pigs in Experiment 178-F was greater than that
of Baker's pigs. The depression in feed intake in Experiment 178-E
was attributed to high ambient temperature. It has been demonstrated
(Wallace et al., 1967; Baker et al., 1967) that pigs fed DES + MT
respond to the hormone more markedly at higher protein levels. It
may have been that the pigs in Experiments 178-E and F did not consume
sufficient protein to allow normal nitrogen retention.
This overall depression in feed intake observed in all pigs in
the metabolism trials may have affected the response to DES + IT,
since 65 kg pigs under normal conditions would consume about twice
as much feed as did these pigs, which were confined in metabolism
crates. In addition to this overall decrease in feed intake attributed
to stressful experimental conditions, the pigs fed DES + MT showed
the typical depression in feed intake characteristic of hormone fed
pigs. This difference in feed intake between control and treated pigs
may have caused the slight reduction in nitrogen retention in pigs
fed DES + MT, although the feed factor was accounted for in calculations.
Heat and confinement stress may have been directly responsible for
the lack of significant responses to DES + MT.
On the other hand, all pigs in these trials exhibited a positive
mean nitrogen balance which would indicate that some anabolism was
taking place. In fact, all pigs on both treatments did show a weight
gain from the initial to the final weighing. Growth (protein synthesis)
may have been occurring at the maximum possible rate under the experi-
mental conditions. If this was the case, the body protein stores of
the pigs may have been filled; therefore, no further anabolism under
prevailing conditions might be expected to occur in response to OES + MT.
Other workers (Leathem, 1956; Applezweig, 1962) report that
when the body protein stores are filled, little or no anabolic response
to hormone therapy occurs. Robinson and Singleton (1966) were able
to demonstrate an anabolic response in pigs fed a low protein diet,
but not in pigs fed a high protein diet, when an anabolic steroid
hormone was administered.
Variation in feed intake between individual pigs and variation
from day to day in the same pig were both considerable. This was
reflected in a marked variation in nitrogen retention between pigs
and within pigs between days.
A test of the variation between pigs is available. Dividing
sampling error mean square into experimental error mean square
(Tables 40 and 42) gives an F with 3 and 40 degrees of freedom. In
both of the metabolism trials conducted in this study, there was a
significant variation in nitrogen retention between experimental
units (pigs), regardless of block or treatment.
Certainly there are factors which are often beyond experimental
control which can influence the results of a trial. The nitrogen
balance experiments conducted in this study do not give evidence
for a protein anabolism due to DES + MT, despite the fact that a
response favoring increased nitrogen retention might be expected
from the use of such compounds.
The Effects of DES + MT on the
Excretion of Urinary 17-ketosteroids in Swine
Since one of the hormones fed in these experiments, methyl-
testosterone, is excreted in a conjugated ketone derivative form in
urine, a determination was made in the two metabolism trials to de-
tect 17-ketosteroids in urine. These substances are metabolic end
products of steroid hormones of all types.
A significantly greater amount of 17-ketosteroids was excreted
by pigs fed DES + MT in the first metabolism trial. No significant
difference due to treatment was observed in the second trial, although
there was a trend toward a lower excretion of 17-ketosteroids in
the treated pigs. Pigs in Experiment 178-E did not excrete as much
total urine per day as did those in Experiment 178-F. It was noted
that the 17-ketosteroids were more difficult to detect in dilute
urine than in concentrated urine. There also appeared to be great
individual variation among pigs with regard to urinary output and
Adrenal hormone output influences output of 17-ketosteroids, and
it may be that the individual metabolisms of the pigs accounted for
more variation than did the hormone present in the diet. Pigs were
consuming only 3.5 to 5.5 mg of hormone per day.
The feed intake of barrows differed between the two metabolism
trials, and this factor may have influenced the results obtained.
Dorfman and Shipley (1956) state that in humans the normal daily ex-
cretion of urinary 17-ketosteroids varies with age, sex, stress
factors, and endogenous hormone therapy. In this study, DES + MT
did not appear to consistently affect the excretion of 17-keto-
steroids in urine of swine.
Work reported by researchers studying DES and MT indicates that,
fed alone or in combination, these humoral substances affect the
performance and carcasses of pigs. The exact mechanism of action
remains unclear at this time. There is reason to believe that some
of the response in carcass leanness attributed to DES + MT may be
due to the reduced feed intake commonly observed when this combina-
tion of hormones is fed to pigs. The improved lean to fat ratio
resulting when pigs are fed on an energy restricted diet is well
Baker et al. (1967) reported that loin eye area response to DES +
MT is generally improved at higher levels of protein; they postulated
that this points to a protein-anabolic action. This alone, though,
cannot explain all the common responses to DES + HT. The reduction
in backfat thickness coLmmonly seen has been attributed to a possible
antilipogenic action of DES + MT. Decreased backfat thickness may
also be a factor in the increased yield of lean primal cuts observed
in 3 trials in this investigation and by other workers. A change in
rate of deposition of either protein or fat would be reflected in the
leanness criteria used in these experiments.
In regard to the stimulation of increased boar odor incidence,
the value of feeding DES + MT is questionable. Some treated pigs in
the first 2 trials exhibited very undesirable odor and flavor in
the meat; however, in the second 2 trials the meat odor and flavor
was acceptable for most pigs even though some incidence of boar odor
in treated pigs was evident to the trained taste panel. The boar
odor present in the carcasses of some pigs in Experiments 178-A and
B was strong enough to cause condemnation of some carcasses; however,
no carcasses were condemned for odor or flavor in Experiments 178-C
A possible explanation of this might lie in the formulation of the
hormone premix. Researchers at Eli Lilly and Company discovered that
there was a cis-trans isomerism in diethylstilbestrol hitherto un-
known (Herb Brown, personal communication). This isomerism resulted
in a racemic mixture of cis DES (60%) and trans DES (40%) after a
period of time, even though the manufacturing process produced all
trans-DES. Cis-DES was found to be biologically inert in estrogenic
activity, w.hi!e the trans isomer :.a very active. Both forms, however,
showed up in full amount upon chemical analysis. A new stabilized
form of DES was developed which contained 95 percent of the trans
isomer and which would not racemize to the cis form. The first 2
trials were performed using the old type hormone supplement, while
the remainder used the newer stabilized form. It was postulated that
the estrogenic activity of the DES was not sufficient to balance the
androgenic effects of the methyltestosterone in the old type hormone
mixture. This may have caused the strong boar odor and flavor ob-
served in some pigs in the early trials. Incidence of boar odor was
much lower in the later trials using the high-trans stilbestrol mix-
Numerous hormone x sex interactions were observed in all 4 trials.
In general, these interactions were manifested in a different'degree
or direction of response in barrows and gilts. This sex difference
in response to hormone supplementation is probably due to the fact
that barrows have no endogenous source of sex hormones other than the
small amounts produced in the adrenal cortex, whereas gilts have an
ovarian source of natural steroid sex hormones. Doornenbal and Frank-
enham (1969) also observed hormone x sex interactions and concluded
that different proportions of sex steroid hormone supplementation for
barrows and gilts would be necessary to achieve equal responses in
In these experiments, the hormone combination affected perfor-
mance and carcass quality more in barrows than in gilts.
SUMMARY AND CONCLUSIONS
Four feeding and carcass trials and 2 metabolism trials were
conducted to determine the effects of DES + MT on growth, carcass
quality, and nitrogen retention in groi-ng-finishing pigs.
Average daily gain was reduced by hormone supplementation, as
was feed intake. Feed efficiency was generally improved by hormone.
There was a marked and significant trend toward increased carcass
leanness, manifested in a decreased backfat thickness, increased
length, and increased percent of lean cuts, both individually and as
the 4 lean primal cuts. Loin eye marbling, color, firmness, or ten-
derness score were not affected by DES + MT. Chemical composition
of longissimus dorsi was significantly but not consistently affected
by hormone supplementation.
Hormone supplementation produced a significant increase in the
Incidence of boar odor in meat of pigs. This odor was judged un-
desirable and in many cases in early trials, unacceptable.
In later trials, however, the incidence of sex odor was detect-
able and was present to a degree such that the eating quality of the
meat was reduced in some, but not all, cases.
Two metabolism trials failed to show any significant differences
in nitrogen retention, feed intake, weight gain, or digestibility of
dry matter and nitrogen between hormone treated and control pigs.
Excretion of 17-ketosteroids in urine was not consistently affected
A possible protein anabolic effect or antilipogenic effect was
postulated to explain the mode of action of DES + MT in increasing
carcass leanness. It was also noted that the reduced feed intake
common to administration of this combination of drugs was possibly
involved in the carcass leanness response.
As part of the study, the effects of protein level and sex were
also investigated. In general, increasing protein level resulted in
improved performance and carcass quality. Gilts had superior carcasses
to barrows, and were more efficient but gained more slowly than
barrows. Sex and protein level were found to interact with each other
and with DES + MT in influencing many performance and carcass traits.
It was concluded that the mode of action of DES + MT in improving
carcass leanness was unclear. Furthermore, all the effects of DES +
MT on performance and carcass quality in swine are not manifested
The value of DES + MT in improving carcass leanness is fairly
evident, but the problem of boar odor which may appear in the meat
of pigs fed this hormone combination remains unresolved.
This investigation has attempted to define the effects of di-
ethylstilbestrol and methyltestosterone (and their interactions with
other factors) on the performance and carcass quality of finishing
It is the feeling of the author that the effects are fairly well
defined in this ..,'oy, and by other work cited in the literature
review. Future research work on this problem ought to be concen-
trated on defining the mode of action of DES + MT in the body of the
pig. Another area of research which needs to be investigated is
the boar odor problem; some means of reducing the incidence of boar
odor in pigs fed DES + MT may be available. Perhaps another practi-
cal approach to the problem would be the feeding of boars to market
weight, using only a DES supplement to delay or prevent the develop-
ment of the natural boar odor.
At this time, however, DES + MT does not appear to be a
consistently practical approach to improving performance and carcass
quality in pigs, due mainly to the possibility of producing unde-
sirable odor and flavor in meat.
Table 1. Experiment 178. Composition of diets
Protein levels, %
Ingredient 12 14 16
Ground yellow corn (8.9% C.P.) 89.05 84.05 79.05
Solvent soybean meal (50% C.P.) 8.00 13.00 18.00
Defluorinated phosphate (32% Ca; 18% P) 1.80 1.80 1.80
Calcium carbonate (38% Ca) 0.50 0.50 0.50
Iodized salt 0.50 0.50 0.50
Trace mineral premix 35C-73a 0.05 0.05 0.05
Vitamin premix (U.F.)b 0.05 0.05 0.05
Chemotherapeutic premixC,d 0.05 0.05 0.05
Totals 100.00 100.00 100.00
a The composition is shown in Table 3.
b The vitamin fortification is shown in Table 4.
c Basal diets contained tylosin phosphate, 11.0 mg/kg.
d Hormone diets contained 2.2 mg/kg each of diethylstilbestrol
and methyltestosterone and 11.0 mg/kg of tylosin phosphate.
Table 2. Experiment 178. Calculated analysis of diets
Protein levels, %
Calculated analysis 12 14 16
Protein, % 11.93 13.99 16.04
Energy, met. cal./kg 3208 3166 3123
Calcium, % 0.80 0.80 0.80
Phosphorus, % 0.62 0.62 0.62
Vitamin A, I.U./kg 5700 5723 5557
Vitamin D3, I.U./kg 441 441 441
Riboflavin, mg/kg 12.5 12.5 12.5
Niacin, mg/kg 215.4 215.4 215.4
Choline, mg/kg 800.0 800.0 800.0
Vitamin B12, ug/kg 11.0 11.0 11.0
Pantothenic acid, mg/kg 20.0 20.0 20.0
Table 3. Experiment 178. Composition and contribution of trace mineral
% in premix
Level in feed when added at 0.05%
Manganese 10.0 50.0
Zinc 10.0 50.0
Iron 10.0 50.0
Copper 1.0 5.0
Cobalt 0.1 0.5
Iodine 0.3 1.5
a Supplied as manganese sulfate, ferrous sulfate, ferrous carbonate,
iron oxide, copper oxide, cobalt carbonate, potassium iodide,
and zinc sulfate.
Table 4. Experiment 178.
of vitamin premix
Contribution per kg diet
Riboflavin 6.6 mg
Niacin 22.1 mg
Pantothenic acid 13.2 mg
Choline chloride 88.2 mg
Vitamin B12 11.0 pg
Vitamin A 2756 I.U.
Vitamin D3 441 I.U.
Table 5. Experiment 178. Dry matter and protein analysis, % of diets
Protein levels, %
Analysis 12 14 16
Dry matter, % 85.84 86.93 85.53
Crude protein, % (d.m. basis) 12.71 14.58 16.44
Table G. Experiment 178.
Code for marbling score of longissimus dorsi
at 10th rib
Amount of marbling
Practically devoid 1 2 3
Traces 4 5 6
Slight 7 8 9
Small 10 11 12
Modest 13 14 15
Moderate 16 17 18
Slightly abundant 19 20 21
Moderately abundant 22 23 24
Abundant 25 26 27
Very abundant 28 29 30
Extremely abundant 31 32 33
Table 7. Experiment 178. Code for color of longissimus dorsi at
Color of lean Code
Very dark I
Greyish pink (ideal) 3
Lightly light in color 4
Chicken meated very light 5
Table 8. Experiment 178. Code for firmness of longissimus dorsi at
Firmness of lean Code
Medium hard 2
Medium soft 3
Table 9. Experiment 178. Code for boar odor and flavor score
Degree of boar odor or flavor Code
Table 10. Experiment 178-A. Experimental
design and distribution
Treatment factor 1 2 3 4
DES + T + +
Protein level, % 16 16 12 12
Number of pigsa 18 18 18 18
a Each lot consisted of 9 barrows and 9 gilts.
Table 11. Experiment 178-A. Summary of feedlot performance
16% C.P. 16% C.P. 12% C.P. 12% C.P.
Criteria Basal DES + HT Basal DES + MT
Average daily feed, kg 2.62 2.53 2.86 2.74
Average daily gain, kg
(66 days) 0.75 0.75 0.81 0.75
Feed/gain 3.50 3.36 3.54 3.64
-4 c) e
a--) o r~\
alC ) C)
CD 0) 0D
> > C)
<. < u
0 0 0
0o o 0
0 0 0
r0 fQ4 0? -
C C >i -I\ 0 fV
4: -V Ll> o- Lo 0: 3
0C I o0
-'- 3 3 0 2
"' r ,co( nr^ J\ co o -T x cso -tr\Lr- o ro
S- 1- -7 cO r00-- O
0 Cc 0
m 0- -11 rr- c -4 LA- -%CM\-.- 0\CrO -: r\- 0 -C
-0 O 0 C n- M s -- M -0 (/
C' 0 o -7 C l
r .4 C
i o0- D- r-- CM -mrD l N M Y "M r-S 0C- 0 .0
Q 0 al --m'LC4-Cn CmNC-JM-0 0+ U
-Li L\ r- r -- % r- C N
C I .'- ? C9 ,9 r4 *C *- (M r, 4-
m eq ;) W 00210- (1)1o0 'S-! M 0 c
u U '00 1-C C1SLAC'--C' C--- 0 0.
0 I .0 LX r---0
C Z U, I
L L X
E *o In:
' 1- 2: 0*C c 0 o> 0o Ur-\ tflotM0 0
u! NC' A 0COC D- )O'.0 n C'Nr2 NO C'-'c'J Ii
C '-L T t-\ -% - csi r.- ON
o 0C 0
0.- -C--o0O NrOrILr'-o 3
O M u ****no3 m sjc-**o ocLn r*3 (MO
c 0 0 (1 0 . .7 C. 0 0 L. C. 0.
S- C O
E U Un
E 0 0 ) u)
E L.) 4)
U 0 m
'0U, c0\0oO'\o0Cm' OO'M'N-- 00
I- -Y c In 4n 0
I C) LN U -
CO o 000
OI 0 0r
C 0- \o LC ro o 0 m L 0 Lru Lc C \ '- o .
C- 0 LT L--8OP 00 C!"U= O) Oi A- 0 <
E '. E ooI
.0 .7 C' Em- C-- *-S--
0L 4) I4)) 00
X L- 0 U00U
Li 0 0 4O -
U! E u 40 o, L . D. 4- -
Su O OE L - Cc
-' C .' E C- c U X~-
C C C C -'-'U .C- ) L- L CL (/)
4) 0 )o E.-'4-u- .4 C O -L c O
*- Q in < J O O- 0 -J 0n! O E E > 04 -i5
0D 4) < l L ~ i O w J00- L--
I- o L7 C? .?1 h" W lT E -. -0 .. S.L. < u.
O mOC 0 C O
-n \ M- C) n 0 -
-C C- oO c O- -
Lr\c LrOO O c 0 CO -
0 00 cM CO 0 0 -Z
o LA 1 r-7 on co -
co r- Co C14 'rC
c )- (C-4
SL00 -- LA CO -
- C4 !0 CM4 C> CM LA
)N> SC CO -r LA 0 -T
-C O C 0 CO C
o Co en o -
r- r - o o 0-
m m -
e0 Z co
C) r-h r
0, LA CC
r- Co C.
( CO C
E E U
0) oa- )XXXX L -
SLO O 0 j
2 I 0
L 0 LU