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Post-Partum Intervals of Beef Cows Treated with Progesterone and Estrogen

University of Nevada, Reno¹

Abstract

The influence of a series of daily progesterone injections, a single estrogen injection, and a combination of these treatments on various reproductive intervals after calving was studied in 80 pluriparous Hereford cows. Heterogeneity among group variances was found for intervals from calving to first estrus, first ovulation and conception. Treatment significantly decreased the average intervals from calving to uterine involution, estrus, and ovulation. Treatment with progesterone alone appeared to have no influence on conception rate, while cows given progesterone and estrogen or estrogen alone tended to have lower fertility at first estrus. However, the two groups given estrogen had the shortest intervals to conception. Average lengths of the intervals between first and second and second and third ovulations were approximately normal, although some treated cows, especially those given estrogen, had short intervals between the first two ovulations.

¹ Division of Animal Science, Nevada Agricultural Experiment Station Journal Series No. 3. In cooperation with Regional Research Project W-49.