Estimation of Genetic Parameters for Daily Gains of Bulls with Multi-Trait and Random Regression Models

Abstract

The average daily gains of 6,420 Czech Pied bulls (dual-purpose, Simmental type) from 7 breeding stations were analyzed using single-trait animal models, a multi-trait animal model and random regression models. The effects of station, year and season were taken into account by creating herd-year-season classes (HYS) with the season being defined as a 3-month class starting with December. Legendre polynomials of the 1 st to the 4 th degree were used to describe the daily gains within the HYS classes as well as to model bull-specific gain curves. The comparison of the h 2 -values estimated with single-trait models and those gained with a multi-trait model returned only insignificant differences. The comparison of genetic parameters based on the multi-trait model to those from different random regression models shows that polynomials of at least the 2 nd degree are to be used for the genetic analysis of daily gains.