Everglades-tationi Mimeo Report-EES65-17. ..- .... February, 1965
'- RISON OF THREE ANTIBIOTICS FOR WEANLING CALVES/
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,C. EIRaines, R. WT. Kidder and H. L. Chapman, Jr.
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The microbial 6pulaticn of the gastrointestinal tract of ruminants often
include bacteria, protozoa, yeasts and fungi. The broad spectrum antibiotics
have proven their value in the suppression of pathdgehic bacteria in the gastro-
intestinal tract.. Two examples of these antibiotic materials that have been
used under a wide variety of -conditions are chlortetracycline (Aureomycin) and
bacitracin (Bio-Best). It is known that fungi thrive in areas of high moisture
and are common contaminators of the soil.. There is also the probability that
as the growth of bacteria are suppressed in the ingesta a greater build-up of
fungi may occur. An antifungal. agent called nystatin (Mycostatin) has aided in
controlling the fungus Candida albicans in certain animal ingesta..Therefore,
it might be advantageous to include both antifungal and antibacterial materials
in the feed of beef calves.
The object of the study reported herein was to determine whether antibac-
terial and antifungicidal agents would compliment each other in responses by
-In each of three consecutive years, 100 weanling calves were selected and
divided into.five equal groups on the basis of weaning- weights, market grades
and breeding. All calves were born and raised in the station herds and consisted
of purebred Angus, Brahman and Hereford and various crosses of these breeds. The
allotment of calves and the initiation of the study occurred 10-14 days after
Sweating. During this short pretest period, the calves were introduced to a con-
centrate feed mixture and kept in close confinement. In each year, the calves
were all.weaned within a two-day period in the month of June or July.
Upon the initiation of the trial, each group of 20 calves was placed in a
four-acre pasture of Roselawn St. Augustinegrass and provided with an average
of four pounds of a concentrate mixture per head daily. The concentrate mix-
ture was hand-fed daily for 98 daysand consisted of ground snapped corn, citrus
pulp, and cottonseed meal. Antibiotic materials were placed in the concentrate
mixture for the various experimental treatments. The kind of antibiotic and
rate of administration is shown in Table 1.
Test materials were provided by American Cyanamid Company, Princeton, New
Jersey; E. R. Squibb and Sons, New Brunswick, New Jersey; and Premier Malt
Products Company (Pabst Brewing Company), Milwaukee, Wisconsin.
Haines, Kidder and Chapman: Assistant Animal Husbandman, Animal.Husbandman,
and Animal Nutritionist, respectively, Everglades Experiment Staticn, Belle
Table 1. Experimental Design.
Group Calves per Treatments
Number year Agent Daily Rate/Calf
1 20 None (control)
2 20 Chlortetracycline 75 mg.
3 20 Chlortet. + Nystatin 75 & 25 mg.
4 20 Bacitracin 70 mg.
5 20 Bacit. + Nystatin 70 & 25 mg.
The calves were individually weighed at 28-day intervals but only the
differences in initial and final weight were used for comparisons between
treatments. The difference in weight gains of the calves on the various treat-
ments was tested for statistical significance. Market grades, or condition
socres, were placed on each calf at the beginning and end of the study to
determine grade changes due to antibiotic treatments. Data was examined first
by year and then all three years combined for final evaluation of treatment
In the first year, the largest gains occurred in the calves receiving the
chlortetracycline followed by those on the bacitracin treatment. Each of these
antibiotics improved gains when used individually but when nystatin was supplied
in combination with either of them, the gains were depressed. Differences in
the gains by calves receiving nystatin with either chlortetracycline or bacitra-
cin and those receiving either chlortetracycline or bacitracin alone were
statistically significant. However, differences between the gains by calves on
the chlortetracycline or bacitracin treatments were not significant. The average
treatment gains are shown in Table 2.
Responses in the second year were not similar to those recorded for the
first year. All groups receiving the antibiotic materials showed greater gains
than the control'group. The nystatin appeared to-stimulate gains when used in
combination with chlortetracycline but not when in combination with bacitracin.
Differences in gains between treatments were not statistically significant. A
summary of the gains in the second study are also shown in Table 2.
In the third year, the gains of all groups were slightly higher than for
the same treatments in the previous years. The antibiotic materials again im-
proved gains in all groups receiving antibiotics. The greatest response was
registered by calves on the chlortetracycline treatment and the smallest by
those receiving a combination of bacitracin and nystatin. Both chlortetracycline
and bacitracin alone stimulated gains more than when nystatin was used in com-
bination with either of these antibiotics. Differences between treatments for
gains,.were not statistically significant. Table 2 also includes the average
gains made during the third year.
The combined data from the three years indicate that either chlortetracycline
or bacitracin improved the gains of weanling calves in south Florida while nysta-
tin was not effective and in some instances appeared to depress gains. The
variation in responses to the treatments between years was sufficient to be
statistically significant even though differences between treatments themselves
was not quite significant. A significant interaction between treatments and years
also indicated that responses were not consistent. A summary of the combined data
on gains is shown in Table 2.
In the first and third trials, the calves did not maintain their market
grades, but in the second trial market grades were maintained by all groups.
This decline in grade during trials 1 and 3 may have been caused by the calves
losing some of their bloom following weaning which they never regained even
though they gained an average of more than one pound a day in weight. This
gain could have gone into mostly skeletal growth. The combined data, from
the three trials, showed that slight decreases occurred in market grade changes
for all experimental treatments. The differences between treatments for grade
changes were small and not significant. Average market grades are also shown
in Table 2.
Nystatin is recommended for antifungal responses while chlortetracycline
and bacitracin are considered as antibacterial agents. The difference in response
between nystatin and either chlortetracycline or bacitracin treatments suggested
that the organism (Candida species) which nystatin is used for controlling was
not present in calves under these trial conditions. Laboratory tests of fecal
cultures confirmed the fact that Candida albicans was not present in these
calves. Thus, the combining of two antibiotics that affect different organisms
was not beneficial to calves grown under these conditions. However, either of
the two antibiotics that are regarded as antibacterial agents did improve the
gains of the weanling calves.
Table 2. Average Weights and Grades of Calves Treated with Three Antibiotics.
Antibiotic Chlorte- Chlortet. + Bacit. +
Treatment Control tracycline Nystatin' Bacitracin Nystatin
Initial Wt. (ibs) 355 352 358 358 354
Total Gain (Ibs) 117 132 110 126 109
Initial Grade 1/ 8.3 8.4 8.4 8.6 8.6
Grade Change 2 -0.9 -1.0 -1.2 -1.2 -1.2
Initial Wt. (lbs) 402 402 406 405 4o6
Total Gain (lbs) 99 105 113 111 105
Initial Grade 7.2 7.2 7.5 7.2 7.1
Grade Change 0.3 0.4 0.0 0.2 0.3
Initial Wt. (lbs) 401 396 398 398 396
Total Gain (Ibs) 121 133 125 124 122
Initial Grade 7.5 7.5 7.4 7.5 7.4
Grade Change -1.2 -1.1 -0.6 -1.0 -0.9
3 year average
Initial Wt. (lbs) 386 383 387 387 385
Total Gain (ibs) 112 123 116 120 112
Initial Grade 7.5 7.6 7.7 7.7 7.6
Grade Change -0.5 -0.6 -0.5 -0.6 -0.6
6, 7 and 8 refer to low, medium and high standard market grade.
Negative values indicate a decrease in market grade from initial grade.