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Quantifying phenotypic and genetic variation for cow fertility phenotypes in American Simmental using total herd
Cassidy C Catrett1, Sarah E Moorey1, Jon E Beever1
1Department of Animal Science, University of Tennessee, Knoxville, TN 37996, USA.
Journal of Animal Science
|December 19, 2024
Summary
Improving beef cow fertility through genetic selection is crucial for efficiency. This study analyzed reproductive traits, finding that genomic selection can enhance genetic gain for heifer pregnancy and other fertility measures.
Area of Science:
- Animal Genetics and Breeding
- Reproductive Biology in Livestock
Background:
- Reproductive efficiency is vital for livestock production, but traditional selection methods for cow fertility traits are limited due to low heritability and late expression.
- Genetic gain can be accelerated using Expected Progeny Differences (EPDs) to focus selection on predicted genetic merit for reproductive traits.
Purpose of the Study:
- To explore and quantify early and sustained fertility in beef cows using multiple continuous and discrete phenotypes.
- To estimate genetic parameters for various fertility traits using both pedigree and genomic data.
- To assess the impact of genomic data on heritability estimates for reproductive traits.
Main Methods:
- Utilized a large dataset of 533,155 calving records from the American Simmental Association, including genotyped animals.
- Analyzed five fertility phenotypes: calving date (CD), calving interval (CI), first calving interval (FCI), heifer pregnancy (HP), and discrete early calving (DEC).
- Employed pedigree and genomic Restricted Maximum Likelihood (REML) to estimate genetic, permanent environmental, and temporary environmental variance components.
Main Results:
- Pedigree-estimated heritabilities for fertility traits ranged from 0.04 to 0.23, with heifer pregnancy (HP) showing the highest heritability.
- Genomic data incorporation increased the heritability estimate for HP (0.24) and slightly decreased it for FCI (0.04).
- Positive phenotypic and genetic correlations were observed among the analyzed fertility phenotypes, indicating potential for correlated responses to selection.
Conclusions:
- The findings support the use of genomic selection to improve fertility in beef cattle, particularly for traits like heifer pregnancy.
- Further research is needed to optimize genetic predictions and explore the genetic architecture of fertility traits using genome-wide association studies.
- Standardized whole-herd reporting frameworks offer opportunities for novel reproductive phenotype measurement, contingent on consistent and detailed data recording for effective genetic evaluations.
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