Genetic gain & Inbreeding

A method to accommodate variable male reproductive success when managing diversity under mixed mating scenarios

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Abstract

Under multi-sire mating and other mixed mating scenarios, multiple males and females are located in the same facility, and males can freely compete with each other to mate females. Competition between males leads to a skewed distribution of male contributions, giving an increase in mean parental coancestry and a reduction in genetic diversity. The objective of this work was to develop a method to predict this increase in parental coancestry, and to account for this under optimal contributions selection (OCS). The underlying model uses order statistics to help predict the proportion of matings achieved by each male ranked in order of mating success. The two parameters in the model relate to the variability of mating success and the skewness of mating success. This model was fitted using data sets from beef, sheep and fish, where the realised mating success of each male had been recorded, using parent and progeny genotype data. A single parameterisation of the model worked remarkably well across species and numbers of males in each mixed mating group: The numbers of males in the five datasets analysed were (13, 18, 22, 24 and 29); the correlation between predicted and actual numbers of matings per sire, ranked on number of matings realised, averaged 0.967 (range 0.952 to 0.980); and the ratio of s.d. of predicted matings to s.d. of realised matings averaged 1.006 (range 0.839 to 1,396). For practical application it is computationally slow to recalculate parental coancestry in the standard manner when accounting for this increased variation in male contributions. A fast method was developed whereby only the predicted increase in parental coancestry due to variable male reproductive success is calculated, as a function of the fitting of the model presented. This adds almost no time to the computation required to evaluate the increased parental coancestry in an OCS application. For implementation, optimising the allocation of males and females to mixed mating groups uses this increased parental coancestry in the overall objective function, thus removing the optimistic assumption that competing males make equal contributions. One impact is to encourage use of related males within groups - if all males in a group are clones of each other then variable mating success is not a problem - although this can be disturbed by other components in the overall objective function. In conclusion, the method developed works well across the species and numbers of males tested, suggesting good applicability. The method is now being used in several breeding industries.

Keywords: 2026

How to Cite:

Kinghorn, A., (2026) “A method to accommodate variable male reproductive success when managing diversity under mixed mating scenarios”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285344. doi: https://doi.org/10.31274/wcgalp.23650

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