Effect of restricted suckling on ovarian activity and uterine involution in Brahman cows.

Seventy-six Brahman cows and first-calf heifers ranging in age from three to five or more years were used to determine the effects of restricted suckling on postpartum ovarian activity and uterine involution. At 30 days postcalving, cows were randomly assigned to one of two groups: 1)normal suckling (34 cows) and 2)twice-daily suckling (42 cows). The cows were examined by rectal palpation weekly from parturition until the onset of the breeding season. The average interval from parturition to the presence of the first follicle larger than 10 mm (PPFI) was 36.0 +/- 1.0 days, and twice-daily suckling decreased PPFI length 8.1 days (P < 0.01); likewise, first- and second-calf heifers tended to have longer PPFI length (P < 0.05) than cows with three or more calvings. The average interval from parturition to first corpus luteum (PPCLI) was 59.0 +/- 2.0 days. PPCLI was affected by the age (P < 0.05) and weight of the cow at 30 days postpartum (P < 0.10). The average interval from parturition to first estrus (PPEI) was 68.0 +/- 5.0 days. PPEI was affected by suckling (P < 0.10) and month of parturition (P < 0.05). The average interval from parturition to uterine involution was 33.0 +/- 1.0 days. Uterine involution was influenced by month of calving (P < 0.01) and age of the cow (P < 0.05).