Renata Helena Branco, Sarah Figueiredo Martins Bonilha, Dante Pazzanese Duarte Lanna, Leopoldo Andrade de Figueiredo, Liana Calegare, Alexander George Razook
Recent studies of beef cattle feed efficiency suggest an opportunity to select animals to reduce required inputs. Proposed feed efficiency parameters suggested a statistical model to adjust feed intake for differences in average BW and gain (residual feed intake - RFI) or gain adjusted for feed intake (residual gain). RFI is an alternative measurement of feed efficiency, which is theoretically independent of production level and body size. RFI is established by the difference between observed and estimated feed intake based on BW and ADG. The objective of this work was to evaluate the effect of 30 yr selection for post-weaning growth in Nellore on ADG, feed intake, feed conversion efficiency, and RFI. The experiment was conducted at CAPTA Pecuária de Corte - Instituto de Zootecnia, Sertãozinho - São Paulo/Brazil. Feedlot test used 128 heifers from 24 and 25th calf crops, selected for BW and ADG at 550 d of age, from the Selection Program for Zebu Breeds of Sertãozinho. Final BW and ADG were different between lines of selection (control Nellore - NeC; and selected Nellore - NeS), being NeS heifers greaterin BW (280 vs 214 kg) and ADG (1.033 vs 0.777 kg/d) than NeC. DMI expressed in kg (6.90 vs 5.08 kg/d) and in BW percentage (2.82 vs 2.68 %BW) were significantly different. Feed efficiency parameters did not differ: feed:gain ratio (7.12 vs 6.93); gain:feed ratio efficiency (154 vs 157) and RFI (0.045 vs -0.009 kg/d) for lines NeS and NeC, respectively. RFI was favorably correlated to BW, although not different between NeS and NeC lines. Selection for growth did not have influence on efficiency parameters of Nellore heifers.
2009 ASAS ADSA Joint Annual Meeting