Breeding for footrot resistance: A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours at Lincoln University

Abstract

Footrot is a contagious bacterial disease of ruminants caused by the bacterium Dichelobacter nodosus. Endemic and widespread in New Zealand, footrot costs the sheep industry more than 100 million dollars per year from lost production and therapy. This trial verifies is a genetic basis to resistance, shown by significant differences between breeds; Coopworth and Borderdales were more resistant than Merinos. This genetic basis to resistance was also observed between sire lines. The sire line differences observed may reflect ewe selection as there was no randomisation used, even so, this verifies a genetic basis to resistance. The results show that selective breeding in Borderdales produces highly footrot resistant progeny, with over 90% resistant under severe challenge conditions. An association was shown between major histocompatibility complex genes and footrot resistance, supporting the theory that selection could be carried out using gene markers and molecular biology. These results suggest breeding is a sensible option for footrot control. In future the use of reliable genetic markers for footrot resistance could provide a substantial opportunity for farmers to identify superior animals without the need to provide a footrot challenge, as is currently required. Breeding for footrot resistance should enhance the New Zealand sheep industries long-term viability, increasing its ability to compete in a strengthening consumer driven market where chemical-free products from animals managed under good welfare conditions are desired.