Short communication: Heat stress does not affect induced luteolysis in Holstein cows

摘要

Heat stress (HS) has deleterious effects on bovine reproduction,including prolongation of the luteal phasein Holstein cows, perhaps due to compromised luteolysis.The objective was to characterize effects of HS onluteolytic responses of nonlactating Holstein cows given25 or 12.5 mg of PGF_(2α) on d 7 of the estrous cycle. Cowswere randomly distributed into 2 environments: thermoneutral(n = 12; 25°C) or HS (n = 12; 36°C). In eachenvironment, cows were treated with 2 mL of saline,25 or 12.5 mg of PGF_(2α) (n = 4 cows per group). TheHS environment induced a significant increase in rectaltemperature and respiratory rate compared with thethermoneutral environment. Heat stress did not havesignificant effects on luteolytic responses or circulatingprogesterone concentrations. Rapid and complete luteolysisoccurred in all cows given 25 mg of PGF_(2α) and in4 of 8 cows given 12.5 mg; the other 4 cows given 12.5mg had partial luteolysis, with circulating progesteroneconcentrations initially suppressed, but subsequentlyrebounding. Therefore, we conclude that HS does notchange corpus luteum sensitivity to PGF_(2α).