13,14-Dihydro-15-keto prostaglandin F2α release in response to oxytocin challenge early post-partum in anoestrous Nelore cows submitted to temporary calf removal and progesterone priming

Effects of 48-hour calf withdrawal on conception rates of Bos indicus cows and calf weaning weights in extensive production systems

Sixty multiparous Brahman-type cows were randomly selected in the early postpartum period and equally allocated into a calf removal group (RG) and a non-removal group (NRG). Calves from cows in the RG were removed for 48 h prior to the breeding season and returned afterwards, whereas in the NRG, calves remained with their dams until weaning. Weaning weights were corrected to 205 days. Conception rates (CRs) were 76 % for RG and 55 % for NRG but did not differ (p > 0.05). CR was correlated with calving to breeding interval and body condition score at the onset of the breeding season. Product-limit survival curves vs breeding to conception interval differed significantly (p < 0.05) between treatment groups. It was estimated with 95 % certainty that 50 % of the cows in the RG will conceive within the first 12 days of the breeding season, while 39 days were required for cows in the NRG. Weaning weights were 135.2 ± 22 kg for RG and 135.5 ± 19 kg for NRG. It was concluded that 48-hour calf removal prior to breeding season increased the number of cows that conceive early in the breeding season and enhanced conception rates but did not affect calf weaning weights of Bos indicus cattle in extensive production systems.