Influence of environmental heat on peripheral plasma progesterone and cortisol during the bovine estrous cycle.
Plasm progesterone and cortisol were measured in jugular blood by competitive protein-binding assay. Six cycling, estrus-synchronized Guernsey heifers were followed for four consecutive estrous cycles under two controlled temperature (18.2 C, 55% relative humidity; and 33.5 C, 55% relative humidity) conditions. Prolonged exposure to heat of Guernsey heifers increased plasma progesterone on days 2 to 19 of the first cycle and only on days 2 to 8 of the second cycle. However, heat stress depressed plasma cortisol in both cycles and reduced the correlation coefficient between these steroids relative to specific stages of the estrous cycle.
D000818:Animals; D001831:Body Temperature; D002417:Cattle / Q000502:physiology*; D004032:Diet; D004326:Drinking; D004971:Estrus; D005260:Female; D006813:Humidity; D006854:Hydrocortisone / Q000097:blood*; D007601:Jugular Veins; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D013312:Stress, Physiological; D013696:Temperature; D013997:Time Factors
D011374:Progesterone; D006854:Hydrocortisone