Detection of a corpus luteum in apparently anoestrous cows by manual palpation, transrectal ultrasonography and plasma progesterone concentration

Aims. To determine the level of agreement between transrectal ultrasonograp hy, manual palpation and measurement of progesterone in the detection of co rpora lutea in post-partum cows. To evaluate the reproductive performance o f cows not detected in oestrus prior to mating, but detected with a corpus luteum at the start of mating. Methods. Cows from seven herds which were not detected in oestrus were exam ined between 5 and 7 days before the herd's planned start of mating. Ovarie s were examined by palpation and ultrasonography in 160 cows and plasma pro gesterone concentrations were also measured in 103 cows. Insemination dates and pregnancy data were recorded in 159 cows not detected in oestrus but h aving a corpus luteum and 1405 cycling herd mates. Results. The level of agreement between ultrasonography and measurement of progesterone (kappa = 0.74) was higher than with manual palpation (kappa = 0.67) although it was significant for both techniques (p < 0.001). Cows whi ch were not detected in oestrus, but detected with a corpus luteum had a lo nger interval to first service (12 v. 10 days, p < 0.05) and conception (19 v. 15 days, p = 0.01) than cycling herd mates and had a higher empty rate (9.7% v.3.8%, p < 0.001). Conclusions. These data indicate that ultrasonography may provide a better diagnostic tool for examining cows not detected in oestrus than manual palp ation or measurement of progesterone concentration. Cows not detected in oe strus but having a corpus luteum were shown to have significantly poorer re productive performance than cycling herd mates.