Introduction

Romosinuano cattle is a breed originated in Colombia, but in Mexico there are organized breeders since two decades ago. This breed has a small population size in Mexico and no published studies documenting basic aspects to establish a breeding program were found. The objective of this study was to estimate genetic parameters for birth weight (BW) and weaning weight adjusted to 240 d (WW), as well as to document genetic trends for both traits, in the Romosinuano cattle population of Mexico.

Method

The database was provided by “Asociación Mexicana de Criadores de Ganado Romosinuano y Lechero Tropical A. C”. A total of 895 and 517 records of BW and WW were used. The pedigree included 4,537 animals born between 1950 and 2016. Analyses were carried out with the ASReml program. Preliminarily, univariate models were used to identify the best one for each trait, through the likelihood ratio test. The bivariate animal model included the fixed effects of contemporary group (year-herd-season-sex), calving age as linear and quadratic covariate, and the linear covariate proportion of Romosinuano gene. The random effects were direct additive genetic and sire by contemporary group interaction for both traits, plus maternal additive genetic for WW. Genetic trends were estimated using linear regression of average breeding values on birth year of the animals.

Results

Estimations of direct heritability for BW and WW were 0.19 ± 0.09 and 0.21 ± 0.12. Maternal heritability for WW was 0.04 ± 0.05. The proportion of phenotypic variance explained by the interaction of sire by contemporary group were 0.21 ± 0.05 and 0.11 ± 0.08, for BW and WW, respectively. The genetic correlation between BW and WW was strong and positive (0.69 ± 0.28). Genetic trends for BW and WW were not different from zero (P > 0.05).

Conclusion

The heritability estimates for BW and WW showed enough genetic variability to implement a selection program for these traits.

        · resumo em Espanhol     · texto em Espanhol     · Espanhol ( pdf )