~ Department of Animal Science Florida Agricultural
, Animal Science Research Report AL73-8 Experiment Station
November, 1973 Gainesville, Florida /
INFLUENCE OF SEX, GRINDING OF CORN, AND POTASSIUM SUPPLEMENTATION
ON FEEDLOT PERFORMANCE AND CARCASS CHARACTERISTICS
OF PIGS FED CORN AND SUPPLEMENT FREE-CHOICE 1/
H. D. Wallace, A. Z. Palmer, J. W. Carpenter
and G. E. Combs _/
A report published last year (1) indicated that gilts consumed about one
percent more protein than barrows when fed shelled corn and a complete supplement
free-choice (calculated as a complete feed mixture). Gilt gains were below those
of barrows more than normally observed suggesting that free-choice feeding may
nutritionally stress the gilt more than the barrio eire-
ments for protein. The main objective of this st dy was to further inves igate
the relative protein needs of barrows and gilts b4 the fi- ch~c~ e /ethod of
feeding. Secondly, it was of interest to determine the effect of grinding corn
c \S U- niv. of Floridal
as opposed to using shelled corn in free-choice fea H''s" desired
to evaluate potassium supplementation in an effort to confirm results reported
in a previous paper (2).
Twenty-eight barrows and twenty-eight gilts averaging approximately 60
pounds initially were used in the study. The barrows were divided into four
pens of seven pigs each, as were the gilts. Two pens of barrows and two pens
I/ The data published in this report were generated in swine unit experiment
No. 195-F, Barn No. 4.
2/ Wallace and Combs, Animal Nutritionists; Palmer and Carpenter, Meat Scien-
tists, Department of Animal Science.
This public document was promulgated at an annual cost of
$108.66, or elevencents per copy to inform county agricul-
tural directors, ranchers and growers of research results
in swine management and nutrition.
Department of Animal Science
Institute of Food and Agricultural Sciences
of gilts were fed shelled yellow corn and a complete supplement free-choice.
Similarly, two pens of barrows and two pens of gilts were fed ground yellow corn
and supplement free-choice. One pen of barrows and one pen of gilts on each type
corn were supplemented with potassium.
All pigs were self fed in an open shed type barn on partially slotted floors
over manure storage pits.
Composition of the protein supplement fed to all pigs is shown in Table 1.
Table 1. Composition of Protein Supplement
Soybean oilmeal (50%) 47.20
Meat scraps (45%) 25.00
Alfalfa meal (20%) 25.00
Iodized salt 2.00
Trace mineral supplement 1/ 0.40
Vitamin premix (UF) 2/ 0.40
1/ Calcium Carbonate Co., Quincy, Illinois.
Formula 35Z-95. Contains: 20% zinc, 10%
iron, 5.5% manganese, 1.1% copper, 0.15%
iodine, 0.10% cobalt and 2% calcium.
2/ Contains 6,000 mg. riboflavin; 20,000 mg.
niacin; 12,000 mg. pantothenic acid;
80,000 mg. choline chloride; 10,000 mcg.
Vitamin B12; 2,500,000 I.U. Vitamin A;
400,000 I.C.U. Vitamin D3 and 10,000 I.U.
of Vitamin E per pound premix.
3/ Dyna K, a product produced and generously
supplied by International Minerals and
Chemical Corporation, Skokie, Illinois,
was used as a source of potassium. Po-
tassium was added at a level of 1% to
the protein supplement of those pigs
supplemented with potassium.
All pigs were weighed and feed consumption determined at two week intervals.
Slaughtering and carcass measurements were according to previously described
Data were analyzed statistically using the analysis of variance.
Results and Discussion
Results of the experiment are summarized by lots in Table 2 and according to main
variables in Table 3. Table 4 summarizes the sex influence on dietary protein intake.
Table 2. Influence of Sex, Grinding of Corn, and Potassium
Supplementation on Feedlot Performance and
of Pigs Fed Corn and
Lot No. 5 5A 6 6A 7 7A 8 8A
Sex (M = Barrow)
(F = Gilt) M F M F M F M F
Form of corn Shelled Shelled Shelled Shelled Ground Ground Ground Ground
Potassium + + + +
Number of pigs 7 7 7 7 7 7 7 7
Av. initial wt., lb. 59.6 59.2 59.9 59.1 59.6 58.9 59.7 59.4
Av. final wt., lb. 217.7 216.0 218.0 221.1 220.3 218.1 223.4 219.0
Av. daily gain 1.56 1.35 1.48 1.39 1.50 1.48 1.59 1.48
Feed/unit gain, lb.
corn 2.87 2.88 2.84 2.67 2.88 2.52 2.71 2.63
supplement 0.54 0.78 0.56 0.68 0.55 0.66 0.60 0.66
Dressing % 71.3 73.8 70.9 71.0 72.1 73.0 72.9 71.8
Backfat, in. 1.34 1.11 1.27 1.10 1.24 1.24 1.44 1.27
Carcass length, in. 31.1 32.0 30.8 31.9 31.7 31.7 30.8 31.4
Loin eye area, sq. in. 4.00 4.70 4.19 4.92 3.88 4.24 4.38 4.32
% lean cuts 52.1 55.4 53.5 57.8 52.6 53.9 52.0 53.3
Marbling scores a/ 13.9 10.0 13.3 13.0 14.3 15.0 15.9 16.7
a/ Scores were coded from 0 to 33; small = 10-12, modest = 13-15, moderate = 16-18, etc.
Table 3. Summary of Combined Performance and
Carcass Characteristics,as Influenced
by Sex, Grinding
of Corn and Potassium
Number of pigs
Av. initial wt.; lb.
Av. final wt., lb.
Daily gain, lb.
Carcass length, in.
Loin eye area, sq. in.
% lean cuts
Form of Corn
* P < .05
** P < .01
Table 4. Protein Intake (%) By Barrows
and Gilts in Free-Choice
Wt. range (lb.) Period Barrows Gilts
60 96 4 week 15.45 15.47
60 144 8 week 15.19 16.04
60 220 entire 13.66 14.99
I_ _____ _
Daily gain Barrows gained significantly faster than gilts (1.53 vs. 1.43
pounds per day). A comparable number of barrows and gilts fed complete feed
mixtures simultaneously under comparable conditions (2) gained 1.60 and 1.46
pounds per day respectively. Thus results from the present trial tend to confirm
the generally held opinion that pigs fed free-choice usually gain somewhat slower
than pigs fed complete mixed rations. Pigs fed ground corn gained faster (P < .05)
than pigs fed shelled corn. Potassium supplementation did not influence rate of
Feed/gain Feed conversion data were not statistically analyzed due to
experimental design. The mean values obtained indicate a clear difference in
protein supplement consumption per pound of gain (0.56 vs. 0.70 lb.) for barrows
and gilts. In table 4 these differences were calculated as a percentage of a
complete feed mixture and indicate that gilts by choice will consume more than
1% higher level of protein than barrows. Most of the difference observed occurred
after the first four weeks of the trial. Grinding the corn and potassium supple-
mentation both appeared to exert a modest improvement in feed conversion.
Dressing percent Dressing percent was not significantly affected by any
of the variables imposed.
Backfat Barrow carcasses measured significantly more backfat (P < .01)
than gilt carcasses. Numerical values indicated fatter carcasses from pigs fed
ground corn and those supplemented with potassium but these differences were non-
Carcass length Gilt carcasses averaged 31.8 in. compared to 31.1 for
barrows, a highly significant difference. The other variables did not influence
this measurement significantly.
Loin eye area Differences were significant (P < .01) for sex. Barrows
averaged 4.11 sq. in. compared to 4.55 sq. in. for gilts. Pigs fed shelled corn
showed loin eyes of 4.45 sq. in. compared to 4.21 sq. in. (P < .05) for pigs
given the ground corn. Gilts increased in loin eye size relatively more on shelled
corn than barrows resulting in a highly significant sex x form of corn interaction.
Gilts gained relatively slower on shelled corn. This may have influenced carcass
leanness and final loin eye size. Potassium supplementation also increased loin
eye area (P < .05).
Percent lean cuts Gilts yielded significantly higher (P < .01) percent of
lean cuts than barrows (55.1 vs. 52.6). Pigs fed shelled corn yielded 54.7 percent
lean cuts compared to 53.0 for pigs fed ground corn, a highly significant difference.
A significant interaction of sex x form of corn was again apparent. Gilts fed
shelled corn were relatively leaner compared to barrows than gilts fed ground corn.
Potassium supplementation did not increase lean cut out significantly.
Marbling scores Marbling scores were significantly higher (P < .05) for
pigs fed ground corn compared to shelled corn. Other variables did not affect
An experiment involving 56 pigs was conducted to determine the influence of
sex (barrows vs. gilts), corn preparation (shelled vs. ground) and potassium
supplementation on feedlot performance and carcass characteristics of pigs fed
corn and supplement free-choice.
Barrows gained faster than gilts, consumed less protein supplement (calculated
as 1.33% less protein on a complete mixed feed basis) and yielded shorter, fatter
carcasses with smaller loin eye areas that cut out lower percentages of lean cuts.
Grinding of the corn induced more rapid gains and fatter carcasses as indicated
by differences in backfat thicknesses, loin eye area, percent lean cuts and marbling
Potassium supplementation did not improve gains but did result in a signifi-
cant increase in loin eye size (P < .05), an observation not readily explained
on the basis of feedlot performance data.
1. Wallace, H. D., A. Z. Palmer, J. W. Carpenter and G. E. Combs. 1972.
Influence of sex, pen space and feeder holes per pig on protein con-
sumption, feedlot performance and carcasses of pigs fed shelled corn
and supplement free-choice. Fla. Animal Sci. Res. Rpt. No. AL 1972-4.
2. Wallace, H. D., A. Z. Palmer, J. W. Carpenter and G. E. Combs. 1973.
Influence of sex, dietary protein level and potassium supplementation
on feedlot performance and carcass characteristics of pigs. Fla.
Animal Sci. Res. Rpt. No. AL 1973-7.
3. Wallace, H. D., A. Z. Palmer, J. W. Carpenter and G. E. Combs. 1966.
Feed restriction of swine during the finishing period. Fla. Agr. Expt.
Sta. Bul. 706.