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Genetic parameter estimates for lamb survivability as separate traits based on birth type for Polypay, Rambouillet,
Carrie S Wilson1, J Bret Taylor1
1Range Sheep Production Efficiency Research Unit, USDA-ARS, Dubois, ID 83423, United States.
Journal of Animal Science
|July 11, 2026
Summary
Analyzing lamb survivability in sheep breeds reveals that treating single, twin, and triplet births separately significantly increases heritability estimates. This approach allows for more accurate genetic progress in lamb survival rates.
Area of Science:
- Animal Genetics
- Quantitative Genetics
- Sheep Production Systems
Background:
- Lamb survivability is crucial for sheep production profitability.
- Published heritability estimates for lamb survivability are typically low (< 0.05).
- Understanding genetic components of lamb survival is essential for breeding programs.
Purpose of the Study:
- To comprehensively analyze lamb survivability across different birth types (single, twin, triplet) in four U.S. sheep breeds.
- To compare heritability estimates derived from combined versus multivariate analyses of birth types.
- To assess the potential for genetic improvement in lamb survivability.
Main Methods:
- Utilized five random effects models and three fixed effects models for Polypay, Rambouillet, Targhee, and Suffolk breeds.
- Analyzed lamb survivability data from 1980-2024, including birth weight in a linear-threshold model.
- Calculated direct and maternal heritability estimates for combined and separate birth type analyses.
Main Results:
- Heritability estimates were substantially higher when analyzing each birth type separately compared to a combined analysis.
- Direct heritability for singles ranged from 0.111 to 0.311, twins from 0.056 to 0.158, and triplets from 0.183 to 0.199.
- Identified sires with above-average estimated breeding values (EBV) for both direct and maternal lamb survivability.
Conclusions:
- Treating lamb survivability as separate traits for single, twin, and triplet births is recommended due to differing genetic influences.
- Separate analyses yield substantially increased heritability estimates, indicating greater potential for genetic selection.
- Genetic progress in lamb survivability is achievable through targeted breeding strategies based on birth type.
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