Unraveling the interplay between host genetics, immunity, and microbiota in gastrointestinal parasite resistance in Florida Native sheep

Commodities

Practices

Improved animal resiliency is imperative to achieve sustainable productivity and raise healthy food-producing animals while decreasing reliance on chemical treatments. Unraveling the role and critical interactions between genetic features and gastrointestinal microbiome in immune response development to enhance gastrointestinal nematode resistance in sheep production has a direct impact on animal welfare, health, and system profitability. The ability of animals to fight infections is indicated by the development of immune responses to novel and recurrent antigens. Immune responses can be broadly classified as cellular or antibody-mediated immunity. Strong responses of each type of immunity are associated with improved protection against infectious diseases and parasites. The strength of immune response is a heritable trait; therefore, the objective of this project is to identify the effect of animal genetics and microbiota on the development of immune responses against gastrointestinal parasites in sheep. Our hypothesis is that the increased resistance to gastrointestinal nematodes in the Florida Native sheep breed is due to enhanced immune responses modulated by genetic factors and rumen microbiota population. Our objectives are 1) uncover the contributions of breed and microbiota population to innate and adaptive immune responses to Haemonchus contortus infestation, and 2) identify candidate genes and microorganisms associated with enhanced immunity and resistance to gastrointestinal parasites. The outcomes of this research are expected to lead to practical and effective new solutions that impact animals, farms, consumers, and society as a whole, promoting more sustainable sheep production practices and directly benefiting the Southern sheep industry.

In a preliminary study, our group investigated the effect of breed on antibody-mediated immunity assessed by immunizing Florida Native and Katahdin lambs with a foreign antigen, keyhole-limpet hemocyanin (KLH) (Alvarado-Vargas et al., 2025). Significantly higher anti-KLH IgG concentrations were observed in Florida Native lambs, suggesting a greater ability of this breed to mount a humoral immune response. Notably, Florida Native lambs had lower worm egg counts when raised under the same conditions as Katahdin lambs, highlighting this breed superior resistance to gastrointestinal nematodes. Despite numerous studies on resistance to gastrointestinal nematodes in small ruminants, there is a critical need to understand the roles of host genetic factors and microbiome in immunity and their interplay, and how their relationship modulates host resistance to parasites. The long-term goal of this research project is to provide the Florida sheep industry with novel strategies for improving animal's ability to cope with gastrointestinal parasites, which have direct impact on economic viability of sheep operations, animal welfare and health and food security. The main objective of this research is to identify genetic features and microorganisms underlying the variation in immune responses and enhanced resistance to gastrointestinal parasites in Florida Native sheep. Specifically, this study is focused on:

Objective 1. Determine the influence of breed and rumen microbiota population on the innate and adaptive immune responses to Haemonchus contortus infestation

1. Generate immune response phenotypes due to Haemonchus contortus larvae and adult parasite infestation
2. Determine microbiota composition from rumen fluid samples using sequence data
3. Uncover the contributions of breed and microbiota population to parasite-specific immune responses

Objective 2. Compare host genetic features, immune competence and rumen microbiota composition between parasite-resistant and susceptible sheep

1. Identify parasite-resistant and susceptible animals using weekly worm egg count recorded for 8 weeks after artificial infestation
2. Evaluate animals' ability to mount overall humoral and cellular immune responses by challenging animals with keyhole-limpet hemocyanin (KLH), a foreign antigen
3. Identify candidate genes and microorganisms associated with enhanced immunity and resistance to gastrointestinal parasites

The knowledge and tools generated from this project will have a direct impact on the profitability and sustainability of sheep operations, reducing health-related costs, improving animal welfare, and decreasing reliance on anthelmintics.

The proposed study aligns with the focus area "Increasing Sustainability of Existing Farming Practices".