Physiological, Environmental, and Hormonal Factors at Insemination Which May Affect Conception1,2

Abstract

Rectal and uterine temperatures of lactating dairy cows were recorded at insemination and 14.5±4.6h (mean±standard deviation) later for the first three services. Blood samples were collected from a subcutaneous abdominal vein at the later time. Plasma corticoids and progesterone were quantified by competitive protein-binding analysis. Climatological data were obtained throughout the experiment from September through August. Means and standard deviations of 226 rectal and uterine temperatures at insemination were 38.4±.04C and 38.6±.03C and later, 38.1±.03C and 38.3±.03C. Mean corticoid and progesterone (ng/ml) at the later time were 8.02±.32 and .28±.06. Uterine temperature at insemination; maximum, minimum, and average temperature the day of insemination; and maximum, minimum, and average temperature the day after insemination were associated with variation in conception. Uterine temperatures and average ambient temperature on day of insemination were inversely related to fertility. Progesterone at the later time was related to environmental temperatures on day of insemination. Plasma concentrations of progesterone and corticoids, sampled at the later time postinsemination, had no detectable association with conception.