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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2006-448v1 85/10/2413    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Calegare, L. Articles by Lanna, D. P. D. Search for Related Content PubMed PubMed Citation Articles by Calegare, L. Articles by Lanna, D. P. D.

Energy requirements and cow/calf efficiency of Nellore and Continental and British Bos taurus x Nellore crosses¹

L. Calegare^*, M. M. Alencar, I. U. Packer^* and D. P. D. Lanna^*,2

^* Department of Animal Production, College of Agriculture Luiz de Queiroz, University of Sao Paulo, Piracicaba, Sao Paulo, Brazil; and and Southeast-Cattle Research Center, Embrapa, Sao Carlos, Sao Paulo, Brazil

² Corresponding author: dplanna{at}esalq.usp.br

The objective of this work was to compare breed types with increasing percentage of Bos taurus on cow/calf energy requirements and preweaning efficiency. Forty mature, lactating, nonpregnant cows [10 Nellore (NL), 10 Canchim x Nellore (CN), 10 Angus x Nellore (AN), and 10 Simmental x Nellore (SN)] were randomized in blocks by calving date. Calves from cross-bred cows were sired by Canchim bulls ( Charolais + Zebu), whereas calves from NL cows were sired by Nellore bulls. Cows were individually fed a pelleted diet with 50% hay (alfalfa and coastcross) and 50% concentrate from calving to weaning (20 to 180 d post-partum). Estimated diet ME content was 2.24 Mcal/kg of DM. Individual cow DMI was adjusted every 14 d to keep shrunk BW and BCS constant. Shrunk BW and BCS were 430 ± 12 kg and 4.7 ± 0.09 for NL, 449 ± 10 kg and 4.8 ± 0.09 for CN, 496 ± 10 kg and 5.0 ± 0.09 for AN, and 507 ± 12 kg and 5.1 ± 0.09 for SN. At 40 d calves were allowed ad libitum access to the same diet. Milk yield was recorded using a weigh-suckle-weigh technique. Increasing B. taurus percentage had a linear effect (P < 0.01) on ME intake (MEI) of cow/calf pairs: 21.9 ± 0.38 for Nellore, 23.6 ± 0.35 for 31.5% B. taurus (CN), and 25.6 ± 0.27 Mcal/d for 50% B. taurus (AN and SN). Bos taurus percentage was also positively associated with milk production. Nellore calves had lower (P < 0.05) weaning weight (kg) than crossbreds: 167 ± 12 vs. 206 ± 10 for Canchim Nellore (C), 220 ± 11 for Canchim Angus Nellore (A) and 228 ± 11 for Canchim Simmental Nellore (S). Calf body composition was estimated at weaning using the 9-10-11th-rib section. Retained energy (Mcal) was greater (P < 0.05) in A (384 ± 19.9) than in Nellore (298 ± 21.6) and C calves (312 ± 19.8), and was intermediate in S calves (333 ± 21.6). Cow/calf energetic efficiency (kcal deposited/Mcal of MEI by the pair) was greater (P < 0.05) for AN (103 ± 5.3) than NL (84.9 ± 5.9), CN (83 ± 5.3), and SN pairs (83.5 ± 6.1). Difference (P < 0.05) between Continental and British crosses was shown in linear contrasts; SN pairs had greater MEI and lower retained energy than AN. Increasing the B. taurus percentage increased inputs as well as outputs. However, a relatively greater increase in outputs resulted in significantly greater preweaning efficiency. Purebred Nellore had lower ME requirements; however, in an environment without nutritional constraints, crossbreeding improved preweaning biological efficiency.

Key Words: biological efficiency • body composition • crossbreeding • milk production • weaning weight