Animal Husbandry Mimeograph
Series No. 57-1 August, 1956
THE EFFECT OF FEEDING ERYTHROMYCIN
TO GROWING-FATTENING PIGS j
H. D. Wallace, L. Gillespie, G. E. Combs, Jr.
and C. E. Haines 2/
Numerous experiments have demonstrated that certain antibiotics improve the
growth and production efficiency of swine (I). Chlortetracycline, oxytetracycline
and penicillin have proven most effective for this purpose. The chemists' shelf
contains many additional antibiotics which may or may not prove useful when and if
tested. A fairly recently discovered antibiotic, erythromycin, seemed particularly
promising because of its usefulness in human therapy and wide antibacterial spectrum.
A study by Gerard et al. (2) resulted in a growth improvement and an apparent pro-
tein sparing effect when erythromycin was added to the ration of young pigs. An
extensive search of the literature revealed no other reports on the feeding of
erythromycin to swine.
The experiments herein discussed were undertaken to further explore the feasi-
bility of using erythromycin as an antibiotic supplement in swine rations.
Experiment I. Twenty-five purebred Hampshire and twenty-five purebred Duroc
pigs averaging approximately 38 pounds initially were divided on the basis of breed-
and initial weight into five experimental groups of ten pigs each. Each experimen-
tal group was further divided into two pens of five pigs each. The pigs were con-
fined in concrete pens which were cleaned and washed daily. The method of feeding
was by self feeders and the pigs had access to fresh water at all times.
j/ Supported in part by a grant-in-aid from the Eli Lilly Co., Indianapolis, Ind.
2/ Wallace, Associate Animal Husbandman; Gillespie, Research Assist
Assistant Animal Husbandman; and C. E. Haines, Research Assista epar
of Animal Husbandry and Nutrition, University of Florida, Gain ~sile, Flori
The basal ration used in the experiment is shown in Table I. This basal
ration contained approximately 16 percent of crude protein. The pigs in Group I
were fed the basal ration. The pigs in Groups 2 through 5, respectively, received
the basal ration plus 2, 6, 10 and 20 mg. of erythromycin per pound of ration.
TABLE I. COMPOSITION OF BASAL RATIONAL/
Ground yellow corn 77.0
Soybean oilmeal 21.0
Ground limestone 1.0
Steamed bonemeal 0.5
Salt-trace mineral 0.53
1/ Also fortified with thiamine, riboflavin, niacin, pantothenic
acid, pyridoxine, choline chloride, folic acid and vitamin B12.
The experiment started on May 10, 1954 and was terminated after 54 days.
Experiment II. Thirty-two purebred Duroc and Hampshire pigs averaging approxi-
mately:45 pounds initially were divided on the basis of breed and initial weight
into four treatment groups. Each group was further divided into two pens of four
pigs each. Management of the pigs was similar to that used in Experiment I. The
basal mixture fed in Experiment I was also fed in this experiment. Group I pigs
were fed the basal ration. The pigs in groups 2 through 4, respectively, received
the basal ration plus 2, 10 and 20 mg. of erythromycin per pound of feed. The
experiment started on November 6, 1954 and was concluded when the animals reached
a slaughter weight of approximately 195 pounds.
Results and Discussion
Results of the two experiments are summarized in Table 2.
The difference in average daily gains between the various treatment groups
in both experiments was very small and not statistically significant. One of the
most interesting results in the study concerns daily feed consumption. Normally
an increase in feed consumption is observed when effective antibiotics are fed to
swine. In both experiments it can be seen that the addition of erythromycin at
all levels reduced daily feed intake. Recent studies at this Station (3) on the
palatability of antibiotics indicated that pigs have a definite dislike for
erythromycin. However, it is interesting to note that the addition of the anti-
biotic at all levels in both experiments improved feed efficiency. The low level
of 2 mg. per pound of feed was as effective in improving feeding efficiency as
the higher levels of the antibiotic.
Two experiments, involving eighty-two weanling pigs, have been conducted
to determine the effect of adding erythromycin at levels of 2, 6, 10 and 20 mg.
per pound of feed to the ration of weanling pigs fed in drylot.
Average daily gains were not significantly affected at any level of supple-
mentation. Daily feed consumption was reduced at all levels of erythromycin
supplementation in both experiments.
The amount of feed required to produce a pound of gain was decreased as the
result of adding erythromycin to the ration.
- 3 -
TABLE 2. THE EFFECT OF ADDING ERTHRCMYCIN TO THE RATION OF GROWING-FATTENING SWINE
Experiment I Experiment II
Group No. 1 2 3 4 5 1 2 3 4
Mg. erythromycin added
per pound of feed .0 2 6 10 20 0 2 10 20
No. of pigs 10 10 10 10 10 8 7* 8 8
Av. initial wt. lb. 37.1 38.2 38.3 38.5 38.3 45.8 44.3 45.4 45.4
Av. final wt. lb. 105.9 107.5 108.4 108.3 107.0 192.9 197.3 196.8 195.0
Av. daily gain lb. 1.28 1.29 1.30 1.30 1.28 1.54 1.59 1.60 1.60
Av. daily feed consumption Ib. 3.91 3.72 3.85 3.76 3.71 5.87 5.44 5.49 5.58
Feed per lb. gain lb. 3.06 2.90 2.96 2.91 2.92 3.81 3.42 3.43 3.49
Av. No. days on test 54 54 54 54 54 95.4 96.0 94.5 93.6
*One pig removed early in experiment because of
1. Braude, R., Wallace, H. D. and Cunha, T. J. The value of antibiotics in the
nutrition of swine: A Review. Antibiotics and Chemotherapy 3: 271-291, 1953.
2. Gerard, W. E., Read, 0. C., and Pensack, J. M.
several antibiotics on chick and swine growth.
Food Chemistry, 1: 784-788, 1953.
A comparative evaluation of
Journal of Agricultural and
3. Tomlin, Don C. The effect of certain antibiotics upon the palatability of
rations for swine. A thesis presented to the Graduate Council of the Univer-
sity of Florida in partial fulfillment of the Requirements for the degree of
Master of Science in Agriculture. August, 1956.
September 18, 1956