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Department of Animal Science Florida Agricultural
MWmeograph Series No, 63-9 Experiment Station
August, 1962 Gainesville, Florida
ROTATION OF ANTIBIOTICS,.IN SWINE RATIONS
G. E, Combs and H, D, Wallace /
Although the mechanism whereby antibiotics stimulate the growth of
animals is not completely understood it is generally accepted that this
ability is mediated through the microflora in the gastro-intestinal tract.
Continued use could therefore produce resistant strains which could eliminate
or reduce the response obtained with feeding of antibiotics. Such a re-
duction has occasionally been reported .
The study reported herein was initiated to determine if rate and
efficiency of gain were enhanced by periodic rotation of several antibiotics
in the rations of young and growing-finishing swine.
Experimental
Phase I. Ninety pigs weaned at 2 weeks of age were allotted on the
basis of weight and litter to six treatment :groups of fifteen pigs each.
A total of 80 gin. of antibiotic per ton of feed was used during this phase.
This phase of the study was terminated after a 6-week period,
Phase II. Sixty of the original ninety pigs were continued on their
respective treatments until market weight. The antibiotic content of all
rations was reduced to 20 gm. per ton of feed during this phase of the study.
In both phases of this study the pigs were housed in concrete-floor pens
and self-fed ad libitum. The composition of the basal rations is presented
in Table 1. The antibiotic treatments were as follows:
Phase I
Treatment 1 Basal ration.
Treatment 2 Basal + 25 gm. oxytetracycline + 25 gm, chlortet ine
+ 15 gm. penicillin + 15 gm. streptomycin per, A-x-f
Treatment 3 Basal + 80 gm. penicillin-streptomycin-sulfaquinoxaline
mixture (.39:1:1 ratio) per ton. sEP 1962
Treatment 4 Basal + 80 gm. oxytetracycline per ton.
-----'"" ----- --- '" ^*Rfi{-,
1/ Combs and Wallace, Associate "Animal Nutritionist and Animal Nutritionist,
respectively, Department of Animal Science. The assistance of W. E.
Collins and L. S. Taylor, Swine Herdsmen, is acknowledged.
This study was supported in part by funds and materials supplied by
Chas. Pfizer and Co., Merck and Co', Inc. and American Cyanamid Co.
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Treatment
Treatment
5 Treatment 3 for 1st two weeks of experiment; Treatment 4
for last four weeks of experiment.
6 Treatment 4 for 1st two weeks of experiment; Treatment 3
for last four weeks of experiment.
Phase II
Treatment 1 Basal ration.
Treatment 2 -
Treatment 3 -
Basal + 6 gm, oxytetracycline + 6 gm. chlortetracycline +
4 gmr penicillin + 4 gm. streptomycin per ton.
Basal + 20 gm. penicillin-streptomycin-sulfaquinoxaline
mixture per ton.
Treatment 4 Basal + 20 gm. oxytetracycline per ton.
Treatment 5 Rotation of treatments 3 and 4 at 2 week intervals
throughout experiment.
Treatment 6 -Rotation of treatments 4 and 3 at 2 week intervals
throughout experiment.
Results
The average performance data for both phases of this study are summarized
in Table 2.
Phase I. No significant differences in average daily gain were found
among groups which received antibiotic supplementation. Treatment 1 (basal
ration) gained significantly (P = .01) less than the other treatment groups.
The feed required per pound of gain was comparable for all treatments.
Phase II. During this phase no significant differences in daily gain
were found among treatment groups. The extreme variation within treatment 5
undoubtedly contributed materially to this absence of statistical significance.
However, it is evident that with the exception of treatment 5 the final weights
of all antibiotic-supplemented groups were similar; this indicates that little
if any advantage is associated with rotation of antibiotics at the intervals
used in this study. Similar results have been reported when antibiotics were
rotated with each succeeding ton of ration (Minn. Report H-167, 1959).
The greatest reduction in feed required per pound of gain occurred with
the group given the penicillin-streptomycin-sulfaquinoxaline mixture; this
group.required significantly (P = .01) less feed than treatments 2, 5 and 6.
The basal group (treatment 1) gained more efficiently than treatments 5 and
6 (P = .05).
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Summary
Pigs weaned at two weeks of age were fed rations containing either a
single antibiotic or a combination of antibiotics until market weight. At
intervals of approximately two weeks the antibiotics were rotated in two
of the treatment groups,
From 2 until 8 weeks of age the daily gain of all antibiotic-supplemented
groups was significantly higher (P = .01) than the basal group. No significant
differences were found between groups that received a combination of anti-
biotics, a single antibiotic or periodic rotation of the antibiotics. During
the growing-finishing period the average daily gain of all treatments was
comparable. Feed efficiency was depressed when the antibiotics were rotated,
These data indicated that rotation of the antibiotics at two week
intervals did not enhance their growth-promoting properties.
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Table 1. COMPOSITION OF BASAL RATIONS
Phase I
Ingredient 2-6 weeks 6-8 weeks
Ground yellow corn 22.15 76.70
Sugar 22.25 ---
Dried Skimmilk 40.00 --
Soybean meal 9.00 15.00
Tankage --- 4.00
Lard 3,00 ---
Linestone --- .70
Bonemeal 1,00 1.00
Salt ,50 ,50
Trace minerals .10 .10
Vitamin premix 1/ 2,00 2.00
100.00 100.00
1/ Contained the following (gm,): vitamin A (10,000 I.U./gm.), 15;
bitamin D (9,000 I.U./gm.), 11; choline chloride (25%), 200;
pantothenic acid, .80; thiamine, .30; niacin, .25; pyridoxine, .20;
riboflavin, .50; folic acid (3%), 16.6; vitamin B12 (9 mg./lb.),
80; yellow corn, 583.35.
---- -------W---------------------------------------------------
Phase II
126 lb. to
Ingredient To 125 lb. market weight
Ground yellow corn 78.30 84.30
Soybean meal 19.00 13.00
Ground limestone 1.00 1.00
Bonemeal 1.00 1.00
Salt ,50 .50
Trace minerals .05 .05
Vitamin supplement 1/ .10 .10
Vitamin B12 supplement 2/ .05 .05
100.00 100.00
1/ Contained the following per pound: riboflavin, 2000 mg.; pantothenic
acid, 4,000 mg.; niacin, 9,000 mg.; choline chloride, 10,000 mg.
2/ Contained 9 mg. vitamin B12 per pound.
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Table 2. PERFORMANCE OF PIGS FED ANTIBIOTICS
FROM 2 WEEKS OF AGE UNTIL MARKET WEIGHT
Phase I
Treatment No. 1 2 3 4 5 6
No. of pigs 15 15 15 15 15 15
Av. initial weight, lb, 9.0 8.9 8.9 8.9 8.9 8.9
Av. final weight, lb. 39.2 47.3 44.0 45.6 45.3 45.0
Av. daily gain, lb. ,72a .91 .84 .87 .87 .86
Av. daily feed, lb. 1.38 1.72 1.59 1.65 1.64 1.58
Feed/lb. gain, lb. 1.91 1.89 1.89 1.90 1.88 1.84
a Treatment 1 significantly (P = .01) different from remaining treatments.
----- ---------Phase II--
Phase II
Treatment No.
No, of pigs 10 10 10 10 10 10
Av. initial weight, lb. 38.7 47.6 44.5 45.3 43.1 43.3
Av. final weight, lb. 179.0 192.7 192.8 188.9 178.5 196.9
Av. daily gain, lb. 1.54 1.59 1.63 1.58 1.49 1.69
Av. daily feed, lb. 4.67 4.99 4.86 4.93 4.86 4.39
Feed/lb. gain, lb. 3.03 a 3,14 2.98 b 3.12 3.26 3.19
a Treatment 1 significantly (P = .05) different from treatments 5 and 6.
b Treatment 3 significantly (P = .05) different from treatments 2, 5 and 6.
An.Sci.
GEC:rw
8/3/62
1000 copies
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