Derivation of the Omega-3 Index from EPA and DHA Analysis of Dried Blood Spots from Dogs and Cats

SIMPLE SUMMARY: Omega-3 fatty acids have known health benefits for humans, but the extent to which these benefits extend to animals is still being discovered. Any benefits derived depend on achieving specific blood omega-3 levels, and the metric often used in human studies is the Omega-3 Index (O3I). It is a valid measure of omega-3 status reflecting the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content of red blood cell membranes. The O3I is often calculated from an analysis of whole blood dried on filter paper; and how to convert whole blood EPA + DHA into the O3I is well established in humans, but not yet for other species. This study analyzed blood samples from dogs and cats and developed equations to estimate the O3I in both of these species. Having a validated measure of omega-3 status in these animals will facilitate further research to define exactly what blood levels of omega-3 fatty acids are optimal for each species. These levels can then be used by veterinarians and pet owners alike to gauge the amount of supplemental EPA and DHA each animal needs to achieve an optimal O3I. ABSTRACT: The Omega-3 Index (O3I) is the red blood cell (RBC) eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) content expressed as a percentage of total RBC fatty acids. Although a validated biomarker of omega-3 status in humans, little is known about the O3I status of dogs and cats; species in which omega-3 fatty acids have known health benefits. The purpose of this study was to develop equations to predict the O3I in these species from a dried blood spot (DBS) analysis. Random blood samples from 33 dogs and 10 cats were obtained from a community veterinary clinic. DBS and RBC samples were analyzed for fatty acid composition. For both species, the R(2) between the DBS EPA + DHA value and the O3I was >0.96 (p < 0.001). The O3I was roughly 75% lower in dogs and cats than in humans. We conclude that the O3I can be estimated from a DBS sample, and the convenience of DBS collection should facilitate omega-3 research in these companion animals.