Estimation of genotype by climate interaction, variance component and heritability for fertility traits in Holstein population of Iran

Abstract

Introduction: The aim of this study was to evaluate the mutual effects of genotype and
environment and also to estimate genetic parameters for fertility traits (age of first
calving and interval between two calvings) in Holstein cows in different climates of Iran.
Materials & Methods: The required information was collected at Karaj Livestock
Breeding Center between 2001 and 2017. This information was divided into three
moderate, semi-cold and cold environments based on climatic conditions. Covariance
components and genetic correlation were estimated based on the three-trait model and
the restricted maximum likelihood method. Each attribute in each climate was
considered as independent attributes.
Results: The heritability of fertility traits was higher in cold climate and the age of the
first birth and the interval between two births were 0.217 and 0.058, respectively. Also,
these traits performed better in cold climates. The genetic correlation for the age of the
first birth trait was in the range of 0.857 to 0.897, and for the trait of the interval between
two births, it was between 0.487 and 0.859. The estimation of genetic correlation in this
research showed that the mutual effects of genotype and environment, especially for the
trait of interval between two births, caused different genetic expression of animals in
different climates.
Conclusion: These results showed that the mutual effects of genotype and environment
between different climates can change the performance of male cattle and not
considering these effects may cause errors in breeding programs.