Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2008
Publication Date: 5/1/2009
Citation: Calegare, L., Alencar, M.M., Packer, I.U., Leme, P.R., Ferrell, C.L., Lanna, D.P. 2009. Preweaning Performance and Body Composition of Calves from Straightbred Nellore and Bos taurus x Nellore Crosses. Journal of Animal Science. 87(5):1814-1820. Interpretive Summary: Objectives of this study were to evaluate preweaning performance, body composition, and efficiency of calves representing straightbred Nellore (NL), F1, and three-breed-cross systems. Energy requirements, milk production, and efficiency of 39 cow/calf pairs were recorded from straight bred NL cows (10), crossbred (Angus sired) calves from NL cows (ANL), and crossbred calves (CC; Canchim sired:5/8 Charolais 3/8 Zebu) from crossbred cows (ANL and Simmental x NL; SNL, 20). The CC calves consumed the greatest amount of milk, but similar amounts of silage as the NL calves. Conversely, ANL calves consumed the greatest amount of silage, but similar amounts of milk as NL calves. These observations presumably reflected low milk production of the NL cows, but greater growth potentials of crossbred calves. Energy retention was greater by crossbred (ANL=422 Mcal, CC=449 Mcal) than by NL (295 Mcal) calves. The crossbred calves had greater energy intake, greater energy gains and, consequently, were energetically more efficient that NL calves.
Technical Abstract: The objectives of this study were to evaluate preweaning performance, body composition, and efficiency of calves representing straightbred Nellore (NL), F1, and three breed-cross systems. Energy requirements, milk production, and efficiency of 39 cow/calf pairs were recorded from straightbred NL calves from NL cows (10), crossbred (Angus sired) calves from NL cows (ANL: 9), and crossbred calves (CC; Canchim sired: 5/8 Charolais 3/8 Zebu) from Angus x Nellore (ANL) and Simmental x Nellore (SNL) cows (20). Cows and respective calves were individually fed from postpartum to weaning (17 to 190 d postpartum). At 38 d of age, corn silage (7.8% CP, 2.19 Mcal ME/kg DM) was available to calves ad libitum. Milk production at 42-, 98-, 126-, and 180-d postpartum was recorded by weighing calves before and after suckling. The ratio between gross energy and ME of milk was considered 1:0.93. Calves were slaughtered at weaning and the 9-10-11th-rib section removed for body composition estimation. The ANL calves were lighter (P = 0.001) at birth than CC; NL calves were intermediate. At weaning, NL calves were lighter (P = 0.0006) than ANL and CC calves; 169 ± 7.9 vs. 212 ± 8.3 and 230 ± 5.6 kg, respectively. The ANL had greater (372 ± 25; P = 0.005) silage intake than NL (266 ± 24) and CC calves (278 ± 17 Mcal). Milk energy intakes were 669 ± 53, 745 ± 56, and 970 ± 38 Mcal for NL, ANL, and CC, respectively. The ANL calves needed to compensate the lower milk production from NL cows, which supplied less of their energy requirement for growth. Calves from crossbred cows may have gotten a higher proportion of their needs from milk. Crossbred calves had greater (P = 0.0005) retained energy (RE = weaning body energy – birth body energy) than NL calves: 422 ± 24 for ANL and 449 ± 16 for CC vs. 295 ± 23 Mcal for NL calves. Crossbreds had higher (P = 0.10) percentage of chemical fat than NL calves and water percentages were similar (P = 0.12) among groups: 15.3 ± 0.8 and 61.7 ± 0.7 for ANL, 15.0 ± 0.6 and 62.3 ± 0.5 for CC and 13.3 ± 0.8% chemical fat and 63.4 ± 0.7% water of empty BW for NL calves. Calves from Bos taurus crosses had greater (P = 0.08) 44 energetic efficiency (kcal RE/Mcal ME intake) than NL calves: 382 ± 23 for ANL and 364 ± 15 for CC vs. 317 ± 22 for NL. The greater weight gains and the difference in empty body composition at weaning were more than enough to compensate the higher ME intake of crossbreds. In this study, the crossbreeding systems evaluated increased calf performance preweaning.