P.PSH.0813-Resilience on-farm mechanisms, markers and applications: Final Report

Summary

This project focused on the genetic and non-genetic mechanisms enabling productivity under adversity. Faced with the same infection challenge and under the same management conditions, some animals remain productive while others suffer. The actual basis of this resilience is considered an interaction between foraging ability, intake, food conversion efficiency and physiological responses to infection, and there is a possibility that it could be heritable. Exploiting in-born resilience represents a completely novel approach to health management in Australian livestock; utilising this approach is bound to cost producers much less than reliance on pharmaceutical interventions.

This project applied state of the art technology in gastrointestinal immunology and genomics, transcriptomics and microbiome analysis to determine the impacts of co-infections with pathogens and parasites on productivity, gut microbiota and immune performance to clarify determinants of efficient growth, reproduction and gastrointestinal disease resilience. In addition, a range of outstanding issues regarding vaccination, detection, diagnosis and control of Johne’s disease (JD) in sheep and cattle (such as whether animals deemed to be resilient to JD infection are also resilient to induced internal parasite infestation) were also investigated, as was the validity of resilience biomarkers as a diagnostic and predictive tool.

Precise, validated benchmarking tools for animal health and welfare ensures the ability to select, breed and produce animals “fit for purpose”, underpinning the profitability and sustainability of livestock enterprises.

Objectives

The aim of this project was to apply a systems approach to study the whole animal impact of gastrointestinal pathogens, and unravel the processes that drives and modulate efficient physiology, growth, development and reproduction.
The project focused on the following areas:
· understanding gut pathogen interrelationships through co-infections of gastrointestinal parasites and Ovine Johne’s Disease (OJD)
· developing genetic markers for a resilience phenotype index
· host response biomarkers and on-farm management
· pathogen-host interactions and pathogen evolution
· why OJD shedding persists in some flocks despite vaccination.

Key findings

Key findings include:
· Individual animal resilience scores can be assigned and show variability both between and within treatment.
· A flexible working model for resilience in sheep (a resilience index) was developed, however this needs to be applied to a larger cohort on farm to obtain a workable dataset.
· A novel immunological biomarker which can distinguish between infected and noninfected sheep was identified.
· Investigations of a potential of a new marker, CXCL10 (IP10) found that CSCL10 levels may be predictive of disease outcome and can be applied in a similar fashion in relation to vaccine efficacy, allowing sheep with a greater likelihood of succumbing to clinical disease to be detected and removed from the flock prior to reaching a highly infectious disease state.
· A WGS library of over 40 H.contortus larval field isolates has been established. These isolates showed a high level of heterogeneity compared to the reference genome. The WGS data generated will facilitate the application of newly developed genetic tools and in-depth analysis of new candidate genes and regions to assess phenotypic variants.
· Farming practices such as supplementary feeding on the ground and introducing animals from multiple properties or properties with unknown OJD status can contribute to an OJD positivity status and prevalence for farms participating in the vaccination program.

Benefits to industry

Productivity is the key driver of profitability in any livestock enterprise. The ability to link the ‘resilience’ phenotype to genotype would provide producers with an invaluable tool to ensure productivity and profitability by using livestock selected and bred for resilience to a specific disease or generally more ‘resilient’ animals in certain production systems.