Effect of the characteristics of the postpartum onset of ovarian activity on the reproductive efficiency of Holstein cows in pastoral conditions

Abstract

The objective was to evaluate the effect of the characteristics of the onset of the postpartum ovarian activity on the reproductive efficiency of dairy cows. Eighty-four Holstein cows (43 multiparous and 41 primiparous) were utilized and ovarian function was assessed by milk progesterone and ultrasonography. The experimental period was from day 10 postpartum to first breeding. Intervals from calving to: first ovulation, first observed estrus, first service and conception were 35,4± 4,9, 80,8± 8,6, 103,4± 7,1 and 126,8± 9,1 (days, mean± SEM) without differences within categories. Body condition at calving prolonged the interval from calving to first ovulation in primiparous. Estrus detection rate (61,9%), and pregnancy rate (26,2%) were affected by the ovarian activity prior to beginning of the breeding season. Pregnancy rate for cows with two or more estrous cycles prior to breeding was 81% and for cows with none or one previous cycle was 19%. Estrus detection rate was 62% for cows with a normal previous cycle (17 to 24 days) and 38% for cow with a short previous cycle. It was concluded that for a good reproductive efficiency normal ovarian activity must be resumed prior to the beginning of the breeding season.