Towards explaining the fertility gap in farmed Pekin ducks

Abstract Maximising reproductive success is crucial to animal production systems, particularly in meeting global demands for animal products and improving commercially important traits. However, while social interactions and mating strategies are known to influence reproductive success in wild populations, their consideration in agricultural systems remains limited. Using an interdisciplinary framework that combines concepts from behavioural ecology and quantitative genetics in an animal breeding context, we investigated the role of sperm limitation and polygynous mating strategies (female polyandry, male monopolisation of females and male polygamy) in limiting female reproductive success in farmed Pekin ducks ( Anas platyrthynchos domestica ). We assessed the impact of these behaviours on chick production and quantified their genetic and environmental (co)variance. Our results revealed that the number of dam mates positively influenced chick production in female ducks. However, contrary to our expectation, skew in chick paternity (our measure of male monopolisation) was associated with increased female chick production, challenging the hypothesis that male monopolisation limits the sperm available to females and reduces their reproductive success. We found no evidence that male polygamy led to decreased female chick production. Genetic analysis revealed that female mate number and reproductive skew exhibit genetic variance, providing opportunities for targeted selection to enhance chick production. However, there was a negative genetic association between female polyandry and skew in chick paternity, suggesting a trade-off between these traits that would need to be considered in future selection programmes. Our findings highlight how concepts from behavioural ecology can be incorporated into breeding programmes, providing new opportunities to develop effective and sustainable breeding strategies.