A Multifactorial Genetic Approach to Improving Welfare in the Racing Greyhound

Abstract

Greyhound racing is the third largest spectator sport in the UK. The Greyhound industry, however, produces a surplus of unwanted young dogs that do not make the grade to race. The thesis aimed to investigate the effects of genetic and environmental factors on the variation of race performance in British Greyhounds. Furthermore, the thesis aimed to investigate genetic factors involved in the pathogenesis of Greyhound stress fracture injuries, as well as cortisol and heart rate indicators of stress in the racing Greyhound. A total of 1,711,489 race performance results and six-generation pedigree data were compiled for 50,452 Greyhounds competing at 26 British race tracks over a five-year period (2008 to 2012). Environmental (non-genetic) factors of sex, birth year, starting trap and month-year-stadium combination of the race were found to be significantly associated (p < 0.0001) with the performance traits Race Time (over a 480 metre distance), Speed and Rank (over all race distances). In addition, racing age was significantly associated with Race Time (p < 0.0001), Speed (p < 0.0001) and Rank (p < 0.0005). Stadium and number of dogs in the race were significantly associated (p < 0.0001) with both Race Time and Speed. Type of race and race distance were significantly associated (p < 0.0001) with Speed. Univariate mixed animal-model genetic evaluations were performed. Estimated heritabilities were found to be moderate-high for Race Time (0.44), moderate for Speed (0.37) and low for Rank (0.02). Repeatabilities were moderate-high for Race Time (0.56) and Speed (0.52), and low for Rank (0.03). Breeding values were estimated for 73,344 British Greyhounds for each performance trait. Both phenotypic and genetic improvements were observed in Race Time and Speed of British Greyhounds during the study period. This indicates that the current method of breeding based on phenotypic performance is effective for these traits. The study identified, however, that targeted genetic selection based on EBVs would be considerably more efficient. An archive of 237 British racing Greyhound DNA samples was established. In a Genome-Wide Association Study, single nucleotide polymorphism (SNP) genotyping of 21 case (stress fracture) and 24 control (uninjured) DNA samples was performed. No SNPs were found to reach genome-wide significance. The study, however, identified a number of nominally associated SNPs that may be implicated in the pathogenesis of Greyhound stress fracture, and that warrant further investigation. 11 SNPs were significantly associated at the p ≤ 0.0001 level and a further 96 SNPs at the p ≤ 0.001 level. Several of the most significantly associated polymorphisms were identified within or in close proximity to genes involved in bone metabolism pathways. Further work would be required to validate the associations by fine-mapping and targeted sequencing using a larger sample size. Additionally, the study found that high-intensity sprint exercise in Greyhounds results in a significant increase in salivary cortisol concentration, a measure of stress, which is detectable immediately post-race. There were significant differences pre-race and post-race between each Greyhound's paired salivary log cortisol concentration (p = 0.000004) and paired heart rate (p = 0.002). Genetic analysis of British Greyhound race performance, and genetic factors involved in Greyhound stress fracture injuries, have not previously been reported. The results of this work, along with further studies, can be used to inform future Greyhound breeding practices. The responsible use of targeted genetic selection within the industry would result in the production of stronger, better-performing dogs of predictable and superior genetic merit. Importantly, this may improve Greyhound welfare by minimising the number of surplus dogs produced.