A meta-analysis of the effects of creep-feeding supplementation on performance and nutritional characteristics by beef calves grazing on tropical pastures

The objective of this study was to evaluate the effects of creep-feeding supplementation on growth performance and efficiency, feed intake and digestibility for Nellore calves grazing on tropical pastures, using a meta-analytical approach. The dataset was collected from 18 studies, which were carried out between 2007 and 2017, totalling 75 treatment means that represented 832 cow–calf pairs. All studies had a control treatment with no creep-feeding supplementation (non-creep-fed calves) and a wide variety of creep-feeding treatments (creep-fed calves) that were evaluated herein as a daily amount of supplement intake (SUP, g/kg BW, DM basis) and supplemental crude protein intake (SCPI, g/kg BW); dependent variables were evaluated as differential values relative to non-creep-fed calves. Forage DM intake (g/kg BW) decreased linearly as SUP increased (0.43 g/kg BW per each g/kg BW of supplement DM intake), whereas milk DM intake (g/kg BW) was not affected, though total DM intake increased linearly (0.50 g/kg BW per each g/kg BW of supplement DM intake). The fibre digestibility responded quadratically to SUP and SCPI; however, DM digestibility and TDN intake increased linearly as SUP increased. The supplemental weight gain (SWG) responded quadratically as SUP (P < 0.01) and SCPI (P < 0.01) increased, and there was an influence of calf sex. The maximum responses were estimated at 7.6 g/kg BW (SWG, 0.2 kg/d) for bull calves, and at 5.5 g/kg BW (SWG, 0.1 kg/d) for heifer calves. The calculated supplement crude protein content for maximal responses were 225 and 224 g CP/kg DM for bull and heifer calves, respectively. Likewise, supplemental feed efficiency responded quadratically to SUP and SCPI levels. We conclude that creep-feeding improves preweaning weight gain, with calves responding differently according to sex. Nonetheless, the best results in supplemental weight gain are achieved with moderate amounts of protein supplements.