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Some Physiological Manifestations in the Bovine Estrous Cycle during Control with Exogenous Hormones^{1, 2,}

North Carolina State University, Raleigh

Abstract

A group of virgin dairy heifers were used to study the effects of injected progesterone, oral progesterone and oral progesterone followed by estrogen on cervical mucus viscosity and fern pattern formation, rectal temperature, ovarian activity and the occurrence of estrus. Occurrence of estrus and ovulation was inhibited during treatment. The other manifestations tended to follow the trends of the untreated estrous cycles at the time of estrus. Following this period the rectal temperature did not go as high and the cervical mucus scores did not go as low in treated as they did in untreated estrous cycles. As the time of post-treatment estrus approached, the cervical mucus scores failed to increase as rapidly and in most treatments did not reach the same level as during the control estrous period. Rectal temperature at post-treatment estrus also varied between treatments. Variations in physiological manifestations indicated failure of exogenous hormone treatments to completely control the reproduction system.

¹ From the Department of Animal Science, North Carolina Agricultural Experiment Station, Raleigh. Published with the approval of the Director of Research, as paper No. 1892 of the Journal Series.

² Supported in part by a grant-in-aid from Eli Lilly and Co., Indianapolis, Indiana.