Abstract

MARTINEZ VELAZQUEZ, Guillermo et al. Milk composition in Criollo, Guzerat and F1 cows and its influence on weaning weight of calves. Rev. mex. de cienc. pecuarias [online]. 2010, vol.1, n.4, pp.311-324. ISSN 2448-6698.

Data were collected between 2001 and 2003 from Guzerat (G), Criollo (C), Criollo*Guzerat (CG) and Guzerat*Criollo (GC) cows (n = 619 records). Variables analyzed were fat (G%), protein (P%), lactose (L%), non fat solids (SNG%) content in milk expressed as percentages, and total fat (GP), protein (PP), lactose (LP) and non fat solids (SNGP) expressed in kg produced in each lactation. Birth (PN) and 210-d weaning weight (PA210), were analyzed too. Heterosis, direct and maternal genetic effects were estimated as well as the relationship between milk components and PA210. For G%, P%, L%, SNG%, GP, PP, LP and SNGP, models included fixed effects of cow genetic group (GEN), year of calving (A), calving number (NP), postpartum days (D), calving season (E) and two factors interactions (F). For PN and PA210 models included GEN, NP, E, A and F. Residual correlations between PA210 and milk components were estimated. Heterosis was significant (P<0.05) for GP (5.07±1.9 kg), PP (4.97±1.5 kg), LP (7.04 ± 2.1), SNGP (13.48 ± 3.8 kg), PN (-1.3 ± 0.6 kg) and PA210 (12.65 ± 4.2 kg). Direct genetic effects were positive to G (P<0.05) for LP (11.08 ± 3.7 kg), SNGP (16.98 ± 6.6 kg), PN (3.80 ± 1.1 kg) and PA210 (37.60 ± 7.6 kg). Significant correlations (P<0.05) were found between PA210 and GP (016), LP (0.21) and SNGP (0.19). Correlations suggest that quantity of milk components was important to determine weaning weight of calves.

Keywords : Beef cattle; Weaning weight; Milk composition; Correlations.