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Journal of Dairy Science Vol. 35 No. 3 261-265
© 1952 by American Dairy Science Association ®
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The Influence of Antibiotics on Delayed Returns in Artificial Breeding

R. H. Foote and R. W. Bratton

Department of Animal Husbandry, Cornell University, Ithaca, New York

ABSTRACT

A study of 112,312 first-service cows bred artificially during an 8-mo. period immediately prior to the routine addition of 500 units each of penicillin and streptomycin per milliliter of citrate-sulfanilamide-yolk extender revealed that
Figure 1

Figure 2
the 28- to 35-day, 60- to 90-day and 150- to 180-day per cent non-returns were 79.1, 64.1 and 60.3, respectively. The corresponding values for 233,354 first-service cows bred during a 17-mo. period immediately following the change were 82.5, 73.0 and 69.7. The smaller percentage of delayed returns when antibiotics were used is interpreted as indirect evidence for a marked decrease in embryonic mortalities associated with control of infectious agents in semen.

Bulls' fertility (28- to 35-day per cent non-returns) before as well as after the use of antibiotics was negatively correlated with the percentage of delayed returns, indicating that the semen per se also is a source of origin of some of these delayed returns.

The among-bull variance for non-returns to first-service cows was reduced to less than 10 per cent of its original value by the addition of the antibiotics, penicillin and streptomycin, to the citrate-sulfanilamide-yolk extender.

When antibiotics were used, the 150- to 180-day non-return percentages were predicted nearly as accurately from the 28- to 35-day non-returns as from the 60- to 90-day non-returns.






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Copyright © 1952 by the American Dairy Science Association ®.