Resumo

MARTINEZ VELAZQUEZ, Guillermo et al. Milk yield and its relationship to weaning weight of calves from Criollo, Guzerat and F1 reciprocal cross cows. Rev. mex. de cienc. pecuarias [online]. 2012, vol.3, n.4, pp.501-514. ISSN 2448-6698.

Data were collected between 2001 and 2003 from Guzerat (G), Criollo (C), Guzerat x Criollo (GC), and Criollo x Guzerat (CG) cows (n=208 records) to estimate heterosis (hⁱ) and direct (gⁱ) and maternal (g^m) genetic effects for day of peak milk yield (DMP), maximum milk yield (PML), total milk yield (PTL), daily milk yield (PDL), persistency of lactation (PER), and to estimate relationships between PTL and weaning weight adjusted to 210 d of age (PA210). Lactation curve was estimated by the equation Y(n)=n/ae^kn. Variables were analyzed with least squares procedures and mixed models. Final models included effects of genotype of the cow, number, year and season of calving, sex of calf, birth weight as a covariate and two factor interactions. Correlations and regressions were estimated between PA210 and PTL. GC cows had greater production for PML, PTL and PDL (P<0.10) than C and G cows. hⁱ was important (P<0.05) for PML, PTL and PDL. gⁱ were favorable to G (P<0.05) for PML, PTL and PDL. Correlations were important (P<0.05) for all genetic groups. The regression coefficients were 0.044±0.014 (C), 0.037±0.014 (GC), 0.032±0.009 (G) and0.027±0.015 (CG). Calves from C, GC, G and CG cows required 22.5, 27.3, 30.9 and 37.3 kg of milk per each kilogram of weightat weaning. The differences in the efficiency of utilization of milk consumed by calves suggest that different strategies of feeding during lactation should be considered for the production of feedlot calves with C, GC, G and CG cows.

Palavras-chave : Beef cattle; Milk production; Weaning weight; Criollo.