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Nationwide Research in Cattle Reproduction. A Review

Animal Husbandry Department, Cornell University, Ithaca, New York

ABSTRACT

This paper reviews the present trends in research on dairy cattle reproduction in the United States. Gaps in our knowledge are pointed out and suggestions made for work to fill them. A major need is for further work on the study of lifetime reproductive efficiency and the effects of management practices on it. The influence of heredity on the incidence of absolute sterility needs more study. In the field of infectious diseases, search should be pressed for unknown factors, especially for viruses and other sub-bacterial organisms. Little is known about male infertility. In artificial breeding, the role of the semen plasma needs elucidation. It is an open question whether disease affects fertilization of eggs or early embryonic mortality. Some progress is being made, at last, in mapping the early development of the calf. Timing of service for the greatest fertility should be related to ovulation time more closely than is possible at present. The problem of ovulation control, involving the neuroendocrine mechanism, should receive much more attention. Radioactive tracers should be used in the study of sex-steroid hormone metabolism. "Functional sterility" is still an obscure field that needs further investigation.