Polyunsaturated fatty acids (PUFA), which include n-3 and n-6 fatty acids, are essential for the health of both humans and dogs. Consequently, the need to include n-3 fatty acids in commercial dog foods is gaining increasing recognition. Fish is a natural source of n-3 fatty acids; however, with the reduction in the global fish stock, alternate sources of n-3 fatty acids are gaining importance, and one such example is flaxseed oil. Besides the inclusion of PUFA in canine food, the need to cater to breed-specific dietary requirements is also recognised. In the light of this knowledge, the current research project investigated the breed differences in the biochemical (changes to plasma fatty acid composition) and transcriptional (changes to white blood cell inflammatory-related gene expression) responses to n-3 fatty acids from two dietary sources in two different breeds of dogs. Beagles and greyhounds were chosen for their differences in morphology and propensity to obesity.