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 R2 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.

Background The Omega‐3 Index is a test that measures the amount of the long‐chain omega‐3 polyunsaturated fatty acids (n‐3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in red blood cell membranes, which is expressed as a percentage of all fatty acids. However, alpha‐linolenic acid (ALA) from flaxseed oil, which is a short‐chain n‐3 PUFA, is often promoted in pet feed as a n‐3 source, implicitly assuming it is an effective precursor of EPA and DHA. Objective This study was aimed to compare the effect of supplementation with a plant‐based short‐chain n‐3 PUFA source (flaxseed oil, FSO) with a marine long‐chain n‐3 PUFA source (astaxanthin krill oil, AKO) to increase the Omega‐3 Index in dogs. Methods Ten adult Alaskan Huskies of both genders were supplemented daily with 1,155 mg of EPA/DHA from AKO, whereas another 10 dogs received 1,068 mg ALA from flaxseed oil for 6 weeks. Fatty acid and Omega‐3 Index measurements of the two groups were taken after 0, 3 and 6 weeks for comparison. Results The EPA and DHA concentrations increased significantly only in the dogs fed with AKO resulting in a significant increase in mean Omega‐3 Index, from 1.68% at baseline to 2.7% after 6 weeks of supplementation (p < .0001). On the contrary, both EPA and DHA concentrations decreased significantly in the dogs fed with FSO, which led to a significant decrease in mean Omega‐3 Index from 1.6% at baseline to 0.96% at study end (p < .0001). Conclusions The results showed that supplementation of AKO from Antarctic krill led to a significant increase in the Omega‐3 Index in comparison to FSO in dogs. This suggests that preformed marine EPA and DHA sources are needed in dog feeds, as the dietary requirements proposed by feed industry organizations are not met with conversion from short‐chain n‐3 fatty acids.

(1) Background: it is only the longer chain omega-3 polyunsaturated fatty acids (n-3 PUFAs), eicosapentaenoic acid (20:5n-3, EPA), and docosahexaenoic acid (22:6n-3, DHA) and not the shorter chain α-linolenic acid (ALA, 18:3n-3) that have been linked to health benefits. (2) Methods: 45 dogs divided into three groups were first given premium dry food for 38 days (baseline). The O3I was then used as a diagnostic tool to provide a measure of the sum of EPA + DHA in red blood cell membranes given as a percentage of all fatty acids. The dogs were subsequently fed with either krill meal (krill), fishmeal/oil (fish) or flaxseed cake (flax) included in raw food providing daily 416 mg EPA + DHA (971 mg ALA), 513 mg EPA + DHA (1027 mg ALA) and 1465 mg ALA (122 mg EPA + DHA), respectively. (3) Results: the average baseline O3I level of all dogs was low (1.36%), warranting n-3 supplementation. After four weeks, O3I levels were significantly increased in the krill (from 1.36 ± 0.44 to 2.36 ± 0.39%) and fish (from 1.35 ± 0.22 to 1.9 ± 0.35%) groups (p < 0.001). No significant modification of the O3I was detected in the flax animals. (4) Conclusions: only marine n-3 PUFAs resulted in a significantly increased O3I, with dietary krill meal providing the highest increase.

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