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Accessing genotype by environment interaction using within- and across-country test-day random regression sire models
Summary
Genotype by environment interaction significantly impacts Holstein dairy cow milk production. Different sire rankings between Luxembourg and Tunisia indicate importing semen may not improve milk yield in limited input systems.
Area of Science:
- Animal Genetics
- Dairy Science
- Quantitative Genetics
Background:
- Genotype by environment interaction (G x E) is crucial for optimizing livestock breeding programs.
- Understanding G x E in dairy cattle is essential for effective genetic improvement strategies.
Purpose of the Study:
- To investigate genotype by environment interaction (G x E) for milk production traits in first-lactation Holsteins between Luxembourg and Tunisia.
- To estimate genetic parameters for milk yield and persistency in different environments.
Main Methods:
- Analysis of 730,810 test-day (TD) milk records from 87,734 cows across Luxembourg and Tunisia.
- Application of random regression TD sire models with fourth-order Legendre polynomials.
- Estimation of genetic parameters (heritability, genetic correlations) using within- and across-country analyses.
Main Results:
- Lower heritability estimates for milk yield and persistency in Tunisian Holsteins compared to Luxembourg Holsteins.
- Low genetic correlations (0.50 for milk yield, 0.43 for persistency) between the two countries, indicating significant G x E.
- Low rank correlations for sire breeding values, suggesting different sire performance across environments.
Conclusions:
- Milk production is highly dependent on the production environment for Holstein daughters of the same sires.
- Importing high-merit semen may not be an effective strategy for improving milk production in limited-input systems due to G x E.
- Tailoring breeding goals to specific environments is recommended for maximizing genetic gains in dairy cattle.
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