ORIGINAL RESEARCH Effects of 48-hour calf withdrawal on conception rates of Bos indicus cows and calf weaning weights in extensive production systems Rafael José Airone Escrivão & Edward Cottington Webb & Alice Pereira de Jesus Teresa Garcês & Richard Jackie Grimbeek Accepted: 21 March 2012 / Published online: 12 April 2012 # Springer Science+Business Media B.V. 2012 Abstract Sixty multiparous Brahman-type cows were ran- domly 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. Con- ception 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. Keywords 48-hour Calf removal . Beef cows . Conception rates . Reproduction . Weaning weight Abbreviations BCS Body condition score BW Body weight BCI Breeding to conception interval CBI Calving to breeding interval CCI Calving to conception interval CR Conception rate C ww Corrected weaning weight NRG Calf non-removal group RG Calf removal group Introduction In a beef cow–calf operation, the optimum calving percentage can be attained if the first postpartum oestrus and the reestab- lishment of oestrous cycle occur prior to the breeding season. Because of this, many studies focused on the management of factors that influence reproduction in the postpartum period of beef cows (Perea et al. 2008; Pinheiro et al. 2009; Satrapa et al. 2010; Alverez-Rodriguez et al. 2010). The elimination of the suckling stimulus for 48 h in Bos taurus beef cows in intensive production systems results in a higher serum LH concentra- tion as well as pulse frequency and amplitude by 24 h after calf removal, peak by 48 h, and then decrease after calf return (Whisnant et al. 1985). Forty-eight-hour or 120-h calf removal preceding the onset of the breeding season increased the number of cows in oestrus in the early breeding season (Perea et al. 2008). Successful results on the interval from postpartum to first oestrus and conception rates were related to restricted suckling combined with 48-hour calf withdrawal or only the R. J. A. Escrivão (*) : A. P. d. T. Garcês Department of Animal Production, Faculty of Veterinary, Eduardo Mondlane University, Maputo, Mozambique e-mail: rafael.escrivao@uem.mz E. C. Webb Department of Animal and Wildlife Sciences, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria 0002, South Africa R. J. Grimbeek Department of Statistics, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria 0002, South Africa Trop Anim Health Prod (2012) 44:1779–1782 DOI 10.1007/s11250-012-0137-x