Characterization of ovarian activity in postpartum dairy cows using ultrasound imaging and progesterone profiles

Abstract

Ten postpartum dairy cows were monitored for ovarian activity by using a combination of ultrasound imaging and progesterone (P 4) profiles. Blood and milk samples were collected and ovaries scanned rectally starting 2 and 14 days postpartum, respectively, and continuing until 90 days after calving. Ultrasound imaging of the ovaries for the presence of a corpus luteum revealed that four of the ten animals ovulated by 14 days and eight of the ten by 25 days postpartum. Follicular growth occurred in two waves in most of the postpartum estrous cycles. There was no difference between primiparous and pluriparous animals with regard to time to first postpartum ovulation, duration of first estrous cycle, peak plasma P 4 levels or time to uterine involution. Time to first observed estrus was non-significantly greater ( P>0.05) in primiparous than pluriparous cows. The second postpartum cycle was significantly longer ( P<0.05) with greater plasma P 4 concentrations than the first cycle. Maximum corpus luteum diameter as measured by ultrasound imaging was not correlated with the length of the first and second postpartum estrous cycles or with the maximum plasma P 4 in in the first estrous cycle, but was positively correlated with the maximum plasma P 4 in the second postpartum estrous cycle. Milk P 4 profiles were similar in pattern to plasma P 4 profiles, and correlated with the ultrasound results. The present study found ultrasound imaging useful for monitoring postpartum ovarian activity in cattle.