Beef cattle

Heterosis estimates for heifer pregnancy in US beef cattle

---

Abstract

Heterosis, or the increase in productivity resulting from crossbreeding, is expected to have the largest effect on lowly heritable, complex phenotypes; namely, health, fitness, and fertility traits. Understanding and quantifying expected productivity gains from heterosis may be used to inform and improve multibreed genetic evaluations and may inform producer breeding decisions. The objective of this study was to estimate the effects of heterosis on heifer fertility in a large, multibreed beef herd, the germplasm evaluation (GPE) population at the US Meat Animal Research Center. This structured research population is comprised of purebred and crossbred contemporaries representing 18 highly utilized US beef breeds. Heifers (n = 9917) were on average 423 d of age at the start of their first breeding season, defined as date of first bull exposure or first opportunity to be bred via artificial insemination. The average breeding season was 62 d long; resulting pregnancy rate was 85.2%. Heifer pregnancy was defined as a binary trait based on ultrasound pregnancy diagnosis (open vs pregnant) 105 d after the start of the breeding season. Likelihood of heifer pregnancy was fitted using a generalized linear model with a logit link function, including fixed effects of contemporary group and covariates for age at the start of the breeding season, breed composition, and expected heterosis. F1 heterosis was estimated to increase the odds of heifer pregnancy over a purebred counterpart by 65.3% (P < 0.001). Predicted probability of successful heifer pregnancy was estimated at 0.78 (95% CI: 0.69-0.85) in purebreds to 0.86 (95% CI: 0.80-0.90) in F1 animals. The effect of breed on the likelihood of heifer pregnancy ranged between an odds of -38% to 116%, demonstrating significant between breed variation. These results highlight the significant advantage that heterosis offers to crossbred heifers. The USDA is an equal opportunity provider and employer.

Keywords: 2026

How to Cite:

Engle, B., Kuehn, L., Snelling, W. & Thallman, R., (2026) “Heterosis estimates for heifer pregnancy in US beef cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2295130. doi: https://doi.org/10.31274/wcgalp.24332

Rights: 1