USDA researchers analyzed lamb survival records by birth type across Polypay, Rambouillet, Targhee and Suffolk sheep.
Four breeds, 1980 to 2024
USDA Agricultural Research Service researchers analyzed lamb-survival records from the US Sheep Experiment Station for Polypay, Rambouillet, Targhee and Suffolk sheep. The dataset covered 1980–2024 and included 22,284, 25,085, 20,439 and 3,965 observations respectively. The Journal of Animal Science published the work on 27 July 2026.
Birth type changes the analysis
The team compared combined records with separate models for single, twin and triplet births. Direct and maternal genetic influences differed by birth type. In the combined data, estimated direct heritability ranged from 0.013 to 0.071 and maternal heritability from 0.013 to 0.038. The authors found sires with above-average breeding values for both components.