Investigation of the molecular genetic basis of fly-strike resistance in NZ sheep: analysis of the FABP4 gene

Abstract

Introduction: Fly-strike is a major economic and animal welfare issue in both the New Zealand and Australian sheep industry. There are several factors that predispose sheep to fly-strike, such as fleece-rot, urine staining of wool from the crutch and dags. The FABP4 gene has previously been associated with variation in fleece-rot resistance in sheep. There is a strong genetic correlation (r=0.9) between fleece-rot and fly-strike. In this context, this study set out to determine if there is an association between a gene that has previously been linked to fly-strike susceptiblity (FABP4) and susceptibility to disease. Methods and materials:Blood samples were taken from sheep with and without fly-strike at shearing time and from different properties through Canterbury. These samples were collected onto FTA cards for DNA typing. PCR-SSCP analysis was used to genotype a portion of the ovine FABP4 gene. Results: Four variants of FABP4 gene were found (A₁, B₁, C₁ and D₁). there was a difference between sheep with and without fly-strike and the presence/absence of the A₁and C₁ variant, (P=0.0073) and (P=0.0154) respectively. Sheep with the A₁ variant are less likely to get fly-strike than sheep with the C₁ variant. The overall Chi-squared test was insignificant, indicating that it cannot be determined from the genotype whether sheep will or will not get fly-strike. Discussion: Based on these findings the development of a gene marker test for selecting sheep that are genetically resistant to fly-strike is a possibility. However further studies need to be done, with a larger sample of sheep. The exact nature of FABP4 causes sheep to be resistant or susceptible to fly-strike also needs to be determined.