Effect of Monitoring Corpus Luteum Function on Days Open

Abstract

The concentration of progesterone in milk fat was measured to ascertain whether knowledge of corpus luteum function could be used to increase reproductive efficiency. As they calved, 47 cows were assigned to either a milk-sampled group (24) or an unsampled control group (23). Progesterone concentrations indicative of a functional corpus luteum were first present at an average of 29.4 days postpartum. The average postpartum interval to 1st estrus was 49 days for cows sampled and 71.9 days for control cows. The postpartum interval to conception was 84.8 days for sampled cows and 113.7 days for control cows. Twenty of 63 (31.7%) ovulations were not associated with behavioral estrus. Cystic ovarian disease with periods of anestrus were observed in 5 cows. Failure to detect estrus was apparently a more limiting factor in reproductive efficiency than was anestrus. To determine the reproductive status after breeding, progesterone concentrations were measured on days 19 through 23 postinsemination. Progesterone was higher for pregnant than for nonpregnant cows on all days. Only on days 20 and 21 was there complete separation of the progesterone ranges in pregnant and nonpregnant cows.