Optimising fertility in British broiler breeder flocks

Resolving the mechanisms underpinning patterns of variation in fertility is one of the major outstanding challenges in Biology, and a key challenge in livestock production, where breeding for increasing efficiency of resource use has drastic knock-on effects on fertility rates. Fertility is a key determinant of profitability in commercial broiler breeder operations, and remains a considerable limiting factor in broiler productivity in the UK. Marginal (~1%) reductions in fertility cost the poultry industry millions of pounds annually, so the economic benefits of optimizing fertility are obvious. High flock fertility can also be associated with increased bird welfare. As one of the world's premier broiler breeding companies, Aviagen Ltd is a major supplier of grandparent broiler breeder stock to UK industry and globally. The Aviagen breeding program seeks to optimise a range of traits related to reproduction, health, production, environmental impact, robustness, food security, welfare, sustainability, and involves the assessment of >1,000,000 chickens annually. Key to Aviagen's balanced breeding goal is a strong focus to improve reproductive performance, by determining factors underpinning variation in fertility. Variation in broiler fertility has multiple sources: our preliminary analysis of 18 recent Aviagen broiler breeder flocks reveals significant fertility variation across different flocks, within flocks across different individuals, and within individuals as they age over time. This trend is reflected on a national scale. The European Ross 308 breeder (the major UK broiler breed supplied by Aviagen) has a 40-week target hatchability of 83%, but shows large variation in hatchability across UK flocks. While measures to improve fertility can be adopted, such as assisting flocks with replacement males, these measures are not always cost-efficient or effective. Clearly, fertility in broiler breeders has a complex, multifactorial nature, which can only be resolved by simultaneously considering multiple proximate behavioural, physiological and genetic mechanisms. Improved understanding of these correlated factors offers the opportunity for developing new selection and management tools to optimize genetic progress, bird management and thus animal balance and welfare. Key to this pluralistic approach is an understanding of the evolutionary significance of fertility-related traits, and the
way these have changed in broiler chickens through domestication and selection. Here, we propose a Stand Alone LINK research grant, which seeks to resolve the mechanisms underpinning infertility in British broiler breeder commercial stocks, which capitalizes on the synergistic combination of the expertise of TP's lab in the evolutionary ecology of chicken reproductive behaviour and fertility dynamics, and Aviagen research infrastructure and resources and extensive expertise of broiler breeder production and fertility in the UK. Three factors make this project particularly novel and robust. First, a novel automated genotyping technique recently developed by Aviagen, which enables high-throughput, real time parallel parentage assignment in pedigree broiler breeder flocks. Second, a series of quantitative tools and immune-physiological assays newly developed by TP's lab to study fertility at multiple levels, from the social structure of entire populations to in vitro molecular interactions. Third, a well-established partnership between TP and Aviagen through a CASE PhD scholarship, which is generating substantial preliminary results that inform the hypotheses and approaches proposed. We aim to harness these breakthroughs to identify the causes of variation in fertility in Aviagen broiler breeder stocks at three integrated levels: (1) social mechanisms, (2) inherent male or female factors, and (3) male*female incompatibilities.

Resolving the mechanisms underpinning variation in fertility is a key challenge in livestock production, where breeding for increasing efficiency of resource use has drastic knock-on effects on fertility rates. Fertility is a key determinant of profitability in commercial broiler breeder operations, and remains a considerable limiting factor in broiler productivity in the UK. Marginal reductions in fertility cost the poultry industry millions of pounds annually, so the economic benefits of optimizing fertility are obvious. High fertility can also reflect better bird welfare. We propose a Stand Alone LINK research grant, which seeks to understand variation in fertility in British broiler breeder flocks in partnership with Aviagen Ltd. As one of the world's premier broiler breeding companies, Aviagen Ltd is a major supplier of grandparent broiler breeder stock to UK industry and globally. Our preliminary analysis of these flocks reveals substantial fertility variation across different flocks, within flocks, and within individuals as they age over time. This trend is reflected on a national scale. The European Ross 308 breeder (the major UK broiler breed supplied by Aviagen) has target hatchability of 83% with substantial inter-flock variability. Three factors make this project novel and robust. An automated genotyping technique recently developed by Aviagen, enabling high-throughput parentage assignment of broiler breeder flocks. Quantitative tools and immuno-physiological assays developed by TP's lab to study fertility at multiple levels, from population dynamics to in vitro molecular interactions. A well-established partnership between TP and Aviagen through a CASE PhD scholarship, which is generating preliminary results that inform the hypotheses and approaches proposed. We aim to harness these assets to identify the causes of variation in fertility at three integrated levels: (1) social mechanisms, (2) male/female factors, and (3) male*female incompatibilities.

Who will benefit from this research?
1) The main beneficiary of this research will be the POULTRY INDUSTRY in general, and the UK BROILER INDUSTRY in particular.
2) A related beneficiary will be DEFRA in its priority to improve the productivity and competitiveness of British food and farming businesses.
3) NGOs, learned societies and 3rd sector organisations focused on ANIMAL WELFARE (e.g. RSPCA, ASAB).
4) The GENERAL PUBLIC will also be a beneficiary of this research due to the tremendous interest in issues associated with the Food Industry, Food Safety and Animal Welfare.

How will they benefit from this research?
1-2) By ameliorating infertility problems of the broiler breeder industry the proposed research will foster global economic performance, and specifically the economic competitiveness of the British poultry industry.
3) Infertility problems are likely to be associated with poor welfare of the flock, especially through suboptimal mating behaviours, intra- and inter-sexual aggression, which can lead to severe (lethal or sublethal) consequences for members of the flock.
4) By generating new knowledge and disseminating information on the different causes of infertility and how science can help the industry develop more efficient and animal friendly ways to manage flock fertility.