Genetic gain & Inbreeding

Predicted genetic gain under multiple-sire mating compared to single-sire mating

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Abstract

The objective of this study was to compare the predicted genetic performance of multiple-sire mating (MSM) and single-sire mating (SSM) strategies in a beef cattle breeding context, with some focus on how variable male mating success (VMMS) influences genetic gain and diversity. While MSM is quite widely used in commercial and extensive breeding systems, its genetic efficiency relative to optimized SSM has not been well quantified, particularly when VMMS is considered. Data from the Landfall Angus breeding program were used to construct backup matings following artificial insemination, though the candidates reflect what would typically be available for a main-round MSM strategy. Eleven mating groups with specified numbers of males and females, were to be selected from a total of 1493 females and 73 males. Three treatments were evaluated: SSM with 15 to 25 females per male to closely match MSM sire usage, MSM without VMMS correction, and MSM with VMMS correction. Each treatment was assessed under aggressive and conservative diversity management policies. Predicted genetic response was measured as the mean progeny index deviation from the sex-corrected candidate mean. However, preselection of candidates by the breeder means that relative responses do not fully reflect policy performance. When no diversity constraints were applied, MSM achieved a slightly higher maximum response than SSM, because MSM allowed some mating groups to exceed the per-sire mating limits imposed under SSM. This increased the contribution of the highest-index sires, which were allocate to these groups. For similar reasons, MSM without VMMS correction consistently exceeded SSM for genetic response. However, ignoring VMMS is unrealistic. Once VMMS was accounted for, MSM underperformed relative to SSM. This difference was moderate under a policy that is typical in beef cattle, largely targeting genetic gain (MSM = 92.6% of SSM), but much stronger when strong emphasis was put on managing diversity (MSM = 42.9% of SSM). Across all treatments, correction for VMMS increased realised parental coancestry in MSM, confirming that unequal sire contributions substantially erode effective population diversity. In contrast, SSM avoided this penalty by enforcing controlled sire usage, leading to more predictable genetic contributions and superior performance. The absolute magnitude of response differences is influenced by strong preselection of candidates, and therefore probably overstates their long-term impact. Overall, the results indicate that MSM entails a small to moderate genetic compromise compared with SSM, particularly when diversity is actively managed and VMMS is acknowledged. MSM may still offer operational benefits not quantified here, including insurance against infertile sires, simplified mating-group logistics, and fewer management groups contributing to more accurate genetic evaluation. In conclusion, the optimization framework presented substantially improves MSM outcomes and supports its use for backup matings or in systems where single-sire mating is impractical or too costly.

Keywords: 2026

How to Cite:

Archer, F., Jansen, H. & Kinghorn, B., (2026) “Predicted genetic gain under multiple-sire mating compared to single-sire mating”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286196. doi: https://doi.org/10.31274/wcgalp.23878

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