Effects of postpartum nutrition and once-daily suckling on reproductive efficiency and preweaning calf performance in fall-calving Brahman (Bos indicus) cows.

Brahman cows were used to evaluate the effects of postpartum nutrition and suckling on reproductive and calf performance. Cows received high or low TDN and once-daily or unrestricted suckling. High TDN (H; 111% of NRC recommendation) cows received a 75% corn: 25% soybean meal diet. Low TDN (L; 93% of NRC recommendation) cows received no concentrates. Once-daily suckled (restricted, R) cows nursed calves for 30 min/d starting at d 21 after calving. In the unrestricted (U) suckling groups, calves had continuous access to cows. By 2 wk of suckling restriction, more (P < .01) R than U cows had progesterone concentrations of > or = .7 ng/mL (55 vs 0%) and more (P < .05) HR than LR cows had progesterone concentrations > or = .7 ng/mL (70 vs 40%). All groups had increases in progesterone and 13,14-dihydro-15-keto-prostaglandin F2 alpha before estrus. The interval to first estrus was shorter (P < .01) for R than for U cows (42 vs 65 d). By d 42 postpartum, more (P < .01) R than U cows exhibited estrus (67 vs 0%), and more (P < .05) HR than LR cows exhibited estrus (89 vs 44%). Calving interval was shorter (P < .01) for R than for U cows (361 vs 395 d). Initial ADG were lower (P < .01) for R than for U calves (.02 vs .69 kg), but weaning weights were similar. Once-daily suckling permitted ovarian activity, hastened return to estrus, and reduced calving interval without reducing weaning weights. Increased postpartum energy intake enhanced the response to restricted suckling.