Abstract

MARTINEZ NINO, Carlos A; ELZO, Mauricio A; MANRIQUE PERDOMO, Carlos  and  JIMENEZ RODRIGUEZ, Ariel. Genetic parameters and breeding values for live weight using random regression models in a Bos taurus-Bos indicus multibreed cattle population in Colombia. Rev Colom Cienc Pecua [online]. 2012, vol.25, n.4, pp.548-565. ISSN 0120-0690.

Objective: the objective of this research was to estimate genetic parameters and to predict breeding values for live weight in a Colombian Bos taurus-Bos indicus multibreed beef cattle population using random regression models (RRM). Methods: the population included 352 offspring from 37 sires of nine breeds mated to Gray Brahman females. The sire breeds were Gray Brahman, Red Brahman, Guzerat, Blanco Orejinegro, Romosinuano, Simmental, Braunvieh, Normand and Limousin. A longitudinal structured data set comprising 1,090 records was used. First (LP1) and second (LP2) order Legendre polynomials were used to estimate the coefficients of covariance functions. The animal model used included animal age, parity, contemporary group (herd * year * season * sex), breed group, additive genetic and heterosis as fixed effects. Random effects were the direct and maternal additive genetic, and the maternal permanent environment. Residual variances were assumed to be constant along the trajectory (HOM) or to change trough different stages of the growth trajectory (HET). Thus, four RRM (i.e: LP1HOM, LP1HET, LP2HOM, and LP2HET) were compared via Schwartz's Bayesian information and Corrected Akaike's Information criteria. Results: the best RRM model was LP2HET. This model was used to obtain direct and maternal heritabilities (Dh and Mh), correlations, and breeding values. The estimated direct additive covariance function showed that additive genetic covariances increased with age. The Dh was 0.24 at birth, decreased to 0.02 at 132 days, then increased to 0.18 at 492 d. The Mh was negligible throughout the growth period. Direct additive correlation values were moderate (0.43) to high (0.99) and tended to decrease as difference between ages increased. Maternal permanent environmental correlations (MPEC) followed a similar trend. Conclusions: these results suggest that selection for additive direct genetic effects based on weight at an early age would be effective in obtaining heavier animals at advanced growth stages under Colombia's tropical pasture conditions.

Keywords : beef cattle; covariance functions; heritability; heterozygosity.

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