Improving immune competence and disease resistance in sheep by selecting for parasite resistance.

View the project final report

Commodities

• Animals: sheep

Practices

• Animal Production: animal protection and health, genetics, livestock breeding, therapeutics

After June 2023, all US livestock producers will need a veterinarian-client-patient-relationship (VCPR) to be able to get a prescription to purchase any antimicrobial to treat and manage disease. The combination of limited livestock veterinarians and the lack of veterinary use by small ruminant producers creates urgency in identifying alternative strategies to combat disease. The utilization of estimated breeding values within the Katahdin breed has enabled sustainable improvement in resistance to parasites. Recent data indicates that selection for post-weaning worm egg count (PWEC) estimated breeding value (EBV) improves lamb survivability to weaning. Additionally, antibody response to vaccination was greater in Katahdin lambs with lower PWEC values. Taken together, these data provide evidence to indicate that Katahdin sheep with lower PWEC values are more immune competent. To test this hypothesis outside the context of parasitic infection we would need to model a bacterial infection, which can be achieved by using bacterial cell wall products like lipopolysaccharide (LPS). Thus, the objective of this project is to determine effects of PWEC genotype on immune response to LPS. To fully characterize this response, in vitro methodologies will be utilized to evaluate transcriptome-wide differences between PWEC genotypes in response to LPS. These data will be used to support implementation of selection strategies that incorporate PWEC and by doing so would potentially reduce the need for and use of antimicrobials. Reducing disease, the need to treat disease, and preserving the efficacy of medically important antimicrobials is fundamental to the sustainability of small ruminant production.

The approach of this project can be clarified by the objectives below:

1. To characterize differential immune response between LoPWEC and HiPWEC sheep to LPS stimulation in-vitro
2. To determine transcriptome-wide gene expression differences between LoPWEC and HiPWEC-derived cells stimulated with LPS

Funds requested from this proposal will principally be used to characterize immune response and perform transcriptome wide analysis in effort to elucidate patterns in Katahdin sheep with divergent genotypes for PWEC EBV. We intend to use this project as a starting point to allow for a comprehensive genetic analysis of the Katahdin breed in the context of bacterial infections. By using a transcriptome-wide approach, we have the capability to gain new insights into the differences in gene regulation in sheep bred for PWEC which has strong preliminary evidence to regulate immune function. This will give us potential avenues of exploration into the immunoregulation of individuals during a disease state. Fundamentally, we aim to substantiate the claim that selection for PWEC selects for improve immunocompetency outside of just parasitic infections. This work will be presented in the context of improved selection for animal health to producer groups both regionally and nationwide. Additionally, we plan to present findings to scientific community in efforts to build future collaborations that will study this phenomenon on other US sheep breeds.