Variance and covariance components for weaning weight for Herefords in three countries

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Livestock Breeding

Background:

• Weaning weight is a critical trait in beef cattle production.
• Understanding genetic parameters is essential for effective breeding programs.
• Previous estimates of maternal heritability may differ from current findings.

Purpose of the Study:

• To estimate genetic and phenotypic variances for weaning weight in Hereford cattle across the USA, Canada, and Uruguay.
• To determine the homogeneity of genetic parameters for weaning weight across different environments.
• To assess the feasibility of joint genetic evaluation across countries.

Main Methods:

• Utilized large datasets from Hereford Associations in the USA, Canada, and Uruguay.
• Employed a complete animal model and an accelerated EM-REML algorithm for variance component estimation.
• Sampled data by excluding small herds and retaining direct-sire-connected contemporary groups.

Main Results:

• Direct heritability estimates for weaning weight were .24 (USA), .20 (Canada), and .23 (Uruguay).
• Maternal heritability estimates were .16 (USA), .16 (Canada), and .18 (Uruguay), lower than previously used values.
• Total heritabilities were similar across countries (.19, .19, .17), suggesting environmental homogeneity.

Conclusions:

• Genetic and environmental parameters for weaning weight are largely homogeneous across the studied countries.
• Joint genetic evaluation for Hereford cattle is feasible across these environments.
• Genotype x environment interactions appear negligible for weaning weight in this context.