Different selection practices affect the environmental sensitivity of beef cattle

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Reproductive Biology

Background:

• Nellore cattle exhibit varying responses to environmental factors based on selection history.
• Understanding genotype-environment interactions is crucial for effective breeding programs.

Purpose of the Study:

• To assess how different selection practices influence the environmental sensitivity of reproductive and growth traits in Nellore cattle.
• To estimate genetic trends and analyze sire reranking across environmental gradients.

Main Methods:

• Analysis of selection weight, scrotal circumference, and days to first calving data from 1981-2017.
• Application of a reaction norm model with Gibbs sampling to estimate (co)variance components and genetic parameters.
• Estimation of genetic trends for intercept and slope, and examination of sire reranking.

Main Results:

• Heritability estimates for traits varied across lines and environmental descriptors.
• Genetic correlations between intercept and slope differed among traits and lines.
• The NeS line demonstrated higher responsiveness to environmental changes, while NeC and NeT lines showed more modest responses.
• Sire reranking was observed, particularly in NeC and NeT lines, due to weak correlations across extreme environments.

Conclusions:

• Genotype-environment interactions significantly influence Nellore cattle breeding.
• Selection practices differentially affect the environmental sensitivity of Nellore cattle lines.
• Genetic evaluations should incorporate genotype-environment interactions for improved accuracy.