Department of Animal Science Florida Agricultural
Mimeograph Series No. 63-16 Experiment Station
April, 1963 Gainesville, Florida
THE INFLUENCE OF FEED RESTRICTION,
HIGH LEVEL COPPER SUPPLEMENTATION AND SEX
ON THE FEEDLOT PERFORMANCE AND
CARCASS CHARACTERISTICS OF SWINE
H. D. Wallace, A. Z. Palmer, J. W. Carpenter
N. H. Anh and G. E. Combsl/
The need for more efficient production of leaner pork has renewed interest in
the problem of restricting feed intake during the finishing period of market swine.
Certain observations have been well established in this regard. Feed restriction
reduces rate of gain, lengthens the feeding period and increases the percent lean
cut-out. An improvement in feed conversion has been observed in many experiments and
of course feed efficiency is a factor of considerable importance.
High level copper feeding has been investigated at this and other stations. The
danger of copper toxicity is recognized but when fed at safe levels growth responses
have been observed, particularly in young pigs. Very little information has been
obtained on the effects of feeding high levels of copper during the finishing period
The comparative feedlot performance and carcass characteristics of gilts and
barrows is well documented. Gilts gain slower, convert feed to gain more efficiently
and yield leaner carcasses.
The experiment herein reported was undertaken primarily to obtain information on
limited feeding. it was of interest to study the effect of:feeding a high level of
copper during the finishing period and also of particular-interest to determine the
possible interrelationships of feed level, copper 5upplem4n'ation and sex.
Experimental .- c
Sixty-four crossbred pigs were allotted from outcdme groups formed on the basis
of weight, sex and litter to eight lots of eight pigs"each. The ,lot treatments were
as follows: -. -.
Lot I Gilts Limited
Lot 2 Gilts Full-fed
Lot 3 Gilts Limited 125.p.p.m. copper
Lot 4 Gilts Full-fed 125 p.p.m. copper
Lot I-A Barrows Limited
Lot 2-A Barrows Full-fed
I/ Wallace, Animal Nutritionist; Palmer, Associate Meat Scientist; Carpenter, Assis-
tant Meat Scientist; Anh, Graduate Research Fellow; and Combs, Associate Animal
Nutritionist, Animal Science Department. The assistance of W. E. Collins and
L. S. Taylor, Swine Herdsmen; Jeff Jeter, Meats Laboratory Manager and Richard
Newman and Mrs. Barbara Sullivan, Laboratory Assistants is gratefully acknowledged.
Lot 3-A Barrows Limited 125 p.p.m. copper
Lot 4-A Barrows Full-fed.- 125 p.p.m. copper
The experiment was conducted on concrete and the following feed mixture was fed
to all lots. The restricted lots were fed in wooden troughs five pounds of feed per
head per day divided between a morning and evening feeding. Copper sulfate (CuS04
5H20) was the source of copper used in supplementing lots 3, 4, 3-A and 4-A. The
Table I. COMPOSITION OF BASAL FEED MIXTURE
Ground yellow corn 80.35
Soybean meal (50%) 17.00
Ground limestone 1.00
Steamed bonemeal 1.00
Iodized salt 0.50
Trace minerals./ 0.05
Vitamin supplement?/ 0.10
J/ Adds in p.p.m.: Manganese (29.6), iron (36.5), copper (2.5),
cobalt (.83), zinc (42.0) and potassium (3.9).
2/ Adds per pound of ration: vitamin 812 (4.5 mcg.), Niacin (9.0 mg.),
riboflavin (2.0 mg.), pantothenic acid (4.0 mg.) and choline
chloride (98 mg.).
pigs were started on experiment at approximately 100 pounds liveweight and were indi-
vidually weighed off test for slaughter at 200 5 pounds. The pigs were weighed on
and off test in a "full" state of fill. In order to minimize the variation in fill
between full-fed and restricted pigs all animals were weighed off at approximately
9 A.M. or about I hour after the restricted pigs had consumed their morning feed.
The pigs were slaughtered and dressed packer style for carcass study. Carcass
weights and measurements were taken after the carcasses had been chilled for 48 hours
at 34 36 degrees F. Length of carcass was obtained by a measurement from the
anterior edge of the aitch bone (pelvis) to the anterior edge of the first rib.
Backfat thickness was calculated as an average of measurements taken at the first rib,
last rib and last lumbar vertebra. A tracing was made of the perimeter of the
lonaissimus dorsi muscle (loin eye), exposed by cutting the loin perpendicular to the
vertebral column equidistant between the tenth and eleventh ribs. The area of the
loin eye muscle was then determined by use of a compensating polar planimeter. The
carcasses were broken down by a standard procedure (Reciprocal Meat Conference, 1951).
The data were statistically analyzed by the analysis of variance method.
Results and Discussion
Summaries of feedlot performance and carcass data are presented for the indivi-
dual lots in Table 2 and for the main treatment variables in Table 3. The comments
to follow will be directly related to the information as summarized in Table 3.
Level of feeding effect Pigs full-fed gained an average of 1.80 pounds per
head per day compared to 1.36 for the pigs limited to 5 lbs. of feed per day. This
difference was highly significant (P <.01). It is of interest to note that during
the first four weeks of the experiment that both groups gained faster than during
the terminal phase of the experiment. As a result of the slower gains made by..the
restricted pigs an average of 17 days additional time was required to reach slaughter
weight. The amount of feed required per lb. gain was approximately the same for the
restricted and full-fed pigs (3.70 vs. 3.68). Work at the Illinois station has con-
sistently demonstrated about a 10 15 percent saving in feed with a feed restriction
method similar to that employed in this experiment. In the Illinois work the pigs
were individually fed, the feed had been wetted, and.the animals were-shrunk prior to
tabulating final weights. Any one or all of these factors plus the difference in the
type of hogs used may have contributed to results relative to feed conversion. It
did appear that in the present study the 5 lbs. of feed was too severe a restriction
for the animals, particularly during the final days of the experiment.
Full-fed pigs dressed 73.0 percent compared to 70.7 percent for the restricted.
pigs. This difference was highly significant (P <.01) and probably reflects mainly
the difference in finish. Backfat thickness was significantly less forthe re-
stricted pigs (1.15 vs. 1.30). Carcass length favored the restricted pigs by about
0.1 inch but the difference was not significant. Carcass firmness scores indicated
a highly significant difference in favor of the full-fed pigs. Many of the re-
stricted carcasses were soft and exhibited a watery condition in the lean meat. The
average loin eye area was somewhat greater for the restricted pigs but the difference
was not statistically significant. The average weight of each of the four lean cuts
favored the restricted group and the difference was highly significant (P<.Ol) for
the hams. There was a very marked difference in percent of the four lean cuts which
favored the restricted pigs (53.40 vs. 49.72). This difference was highly signifi-
cant (P<.01). In a previous trial of this nature the authors observed that full-
fed pigs yielded a significantly higher percentage of liver. In the present experi-
ment full-fed pigs yielded a slightly greater but non-significant liver percentage.
Copper effect Supplementation of the ration with 125 p.p.m. of copper as
copper sulfate exerted no significant influences on any of the factors studied in
Sex effect Barrows gained slightly faster than gilts during the entire trial,
but this difference was non-significant. Gilts gained more efficiently (P <-05) than
barrows (3.58 Ibs. feed per pound gain compared to 3.81). Dressing percent favored
the gilts but the difference was not statistically significant. Carcasses from gilts
averaged 30.10 inches long while those from barrows averaged 29.55 (P <.01). Gilt
carcasses carried 1.15 inches of backfat compared to 1.30 for barrows (P <.01).
Carcasses from barrows were somewhat firmer but this was a non-significant differ-
ence. Gilt carcasses showed highly significant advantages for loin eye area, weight
of hams, weight of loins and percent four lean cuts (P <.01).
A significant sex x feed level interaction was revealed in the data (P<.05).
Gilts gained relatively faster on the restricted feeding program whereas barrows
gained relatively faster on the full feeding regime.
Sixty-four crossbred pigs (Landrace-Duroc x Hampshire) were fed in a 2 x 2 x 2
factorially designed experiment involving feed level, high level copper supplementa-
tion and sex as the main treatment variables. The pigs were started on experiment
at 100 lb.. weight and slaughtered at 200 lb. Restricted pigs were allowed 5 lb. feed
per head daily divided between a morning and evening feeding. The experiment was
conducted in confinement on concrete floors.
Feed restriction reduced gains and increased by 17 days the time required to
reach market weight. Feed conversion was not improved by feed restriction. Dressing
percent, backfat thickness and carcass firmness were all reduced significantly by
feed restriction. Percent of four lean cuts was increased significantly due to feed
High level copper supplementation did not influence significantly any of the
Gilts gained more efficiently than barrows and produced carcasses which were
significantly longer with less backfat and greater loin eye areas. Ham and loin
weights and percent four lean cuts were significantly greater for gilts.
Gilts appeared to tolerate the feed restriction better than barrows as indicated
by a significant interaction between sex and feed level.
Table 2. Summary of Feedlot Performance and Carcass Data for Individual Lots
Lot Number 1 2 3 4 I-A 2-A 3-A 4-A
Feed Level Limited Full Limited Full Limited Full Limited Full
Copper Level, p.p.m. 0 0 125 125 0 0 125 125
Sex Gilts Gilts Gilts Gilts Barrows Barrows Barrows Barrows
Number of Pigs 8 8 8 8 8 8 8 8
Initial wt., Ib. 100.1 99.8 100.0 99.3 100.8 99.6 99.8 99.8
Final wt., Ib. 199.4 199.0 199.3 200.8 197.6 201.9 197.5 202.9
Daily gain, lb.
First four weeks 1.50 1.95 1.54 1.92 1.38 2.00 1.45 2.04
Entire period 1.35 1.72 1.43 1.76 1.33 1.82 1.34 1.90
Feed per lb. gain, lb. 3.68 3.50 3.56 3.57 3.83 3.85 3.75 3.82
Number days on feed 74 58 72 58 75 56 74 55
Dressing percent 70.6 73.9 71.2 73.3 70.8 72.5 70.0 72.3
carcass length, in. 30.18 29.96 29.94 30.30 29.62 29.42 29.72 29.44
Backfat thickness, in. 1.08 1.19 1.14 1.25 1.16 1.38 1.16 1.40
Carcass firmness scored/ 2.62 2.00 2.75 1.87 2.62 1.75 2.75 1.25
Loin eye area, sq. in. 3.69 3.85 3.85 3.63 3.50 3.35 3.49 3.16
Wt. of hams, lb. 28.84 28.95 28.95 27.78 26.64 26.90 28.37 26.17
Wt. of loins, lb. 23.00 23.74 23.68 22.79 21.68 21.92 22.14 20.80
Wt. of picnics, lb. 13.62 13.32 13.56 13.46 13.25 13.43 13.83 12.71
Wt. of butts, lb. 10.20 10.38 10.18 9.79 9.88 9.75 10.33 9.49
Percent 4 lean cuts2/ 53.80 52.02 53.85 50.26 52.05 49.28 53.91 47.33
Percent liver/ 2.25 2.35 2.36 2.26 2.34 2.48 2.29 2.44
I/ Hard-i, medium hard-2, medium soft-3,
2/ Based on chilled carcass weight
Table 3. Summary of Feedlot Performance and Carcass Data
By Main Treatment Variables
Level of Feeding effect Copger Effect Sex Effect
Comparison : Restricted Full-fed Without With Gilts Barrows
Number of pigs 32 32 32 32 32 32
Initial wt., lb. 100.2 99.6 100.1 99.7 99.8 100.0
Final slaughter wt., Ib. 198.4 201.1 199.5 200.1 199.6 200.0
Daily gain, lb.
First four weeks 1.47 1.98** 1.71 1.74 1.73 1.72
Entire period 1.36 1.80** 1.56 1.61 1.56 1.60
Feed per lb. gain, lb. 3.70 3.68 3.71 3.67 3.58* 3.81
Number days on feed 74 57 66 65 65 65
Dressing percent 70.7 73.0** 72.0 71.7 72.3 71.4
Carcass length, in. 29.87 29.78 29.80 29.85 30.10** 29.55
Backfat thickness, in. 1.15** 1.30 1.23 1.23 1.15** 1.30
Carcass firmness score!/ 2.69 1.72** 2.25 2.16 2.31 2.09
Loin eye area, sq. in. 3.63 3.50 3.60 3.53 3.76** 3.38
Wt. of hams, lb. 28.20** 27.48 27.83 27.84 28.63** 27.04
Wt. of loins, lb. 22.63 22.31 22.59 22.35 23.30** 21.64
Wt. of picnics, lb. 13.57 13.23 13.41 13.39 13.49 13.31
Wt. of butts, Ib. 10.15 9.85 10.05 9.95 10.14 9.86
Percent four -an cuts2/ 53.40** 49.72 51.79 51.34 52.48** 50.64
Percent liver'7 2.31 2.38 2.35 2.34 2.30 2.39
I/ Hard-I, medium hard-2, medium soft-3, soft-4, oily-5
2/ Based on chilled carcass weight
SSignificantly better (P <.05)
** Significantly better (P <.01)