Genotype-environment interaction for growth curve parameters in Nellore cattle using reaction norm models

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Animal Breeding

Background:

• Growth curve parameters in cattle are influenced by genetics and environment.
• Assessing genotype-environmental interaction (GxE) is crucial for effective breeding programs.

Purpose of the Study:

• To evaluate GxE effects on asymptotic weight (A) and maturity rate (K) in Nellore cattle growth.
• To compare different models for estimating GxE effects on growth parameters.

Main Methods:

• Utilized data from 240,800 pasture-raised Nellore cattle.
• Employed a standard animal model (AM) and four hierarchical reaction norm models (HOHRNM1S, HOHRNM2S, HEHRNM1S, HEHRNM2S).
• Identified the HOHRNM1S model as the best fit for both A and K parameters.

Main Results:

• Heritability estimates for A and K were 0.45 and 0.47 with AM, respectively.
• Heritability increased with improved environmental conditions under HOHRNM1S, ranging from 0.24-0.82 (A) and 0.34-0.87 (K).
• High correlations between reaction norm intercepts and slopes suggest superior genotypes respond better to environmental improvements.

Conclusions:

• GxE effects are evident and should be included in genetic evaluations for A and K in Nellore cattle.
• Environmental-specific selection using genetically plastic sires can enhance Nellore breeding program efficiency in Brazil.