The effect of dietary camelina, flaxseed, and canola oil supplementation on skin fatty acid profile and immune and inflammatory responses in healthy adult horses.

Abstract

Camelina sativa is an oilseed crop rich in α-linolenic acid (ALA), an n-3 fatty acid (FA), and is resistant to harsh climates and pests. Previously, supplementation with camelina oil (CAM) in horses had no adverse effects on basic health parameters and had comparable skin and coat parameters as both flaxseed oil (FLX) and canola oil (OLA). Further, the plasma FA profile of horses was reflective of their respective treatment oil. The objective of this study was to assess the effects of dietary CAM supplementation on skin FA profile, immune, and inflammatory responses as compared to 2 commonly used oils in the equine industry, OLA and FLX, in healthy adult horses. Twenty-four adult horses, from 2 separate herds, were enrolled in this experiment. The horses underwent a gradual 4-wk fat acclimation period to sunflower oil (approximately 0.28% ALA), then were supplemented with either CAM (approximately 34.9% ALA), OLA (approximately 12.0% ALA), or FLX (56.0% ALA) at an inclusion rate of 0.37 g/kg body weight (BW) per day for an additional 16 wk. Immune and inflammatory responses were assessed by measuring antibody concentrations across time after sensitization to keyhole limpet hemocyanin (KLH) at weeks 10 and 12, and a subsequent delayed-type hypersensitivity (DTH) challenge. Skin biopsy samples were collected at weeks 0, 8, and 16, and FA composition was determined using gas-chromatography. All data were analyzed as a repeated measures ANOVA using PROC GLIMMIX in SAS. Antibody and DTH responses to KLH did not differ among groups (P = 0.262 and 0.813, respectively), and no treatment by time effects were observed (P = 0.764 and P = 0.817, respectively). Most FA in the skin changed in composition across time, with the sum of n-3 FA increasing (P < 0.001) and the sum of n-6 FA and skin n-6:n-3 ratio decreasing over time (P < 0.001 and P < 0.001, respectively). Only dihomo-γ-linolenic acid (P = 0.025) and the sum of n-3 FA (P = 0.031) had treatment-by-week effects. At week 16, the composition of eicosapentaenoic acid in the skin was greater in FLX than OLA, but neither differed from CAM (P = 0.049). These results suggest that ALA supplementation may beneficially impact skin FA profile. However, due to the small differences in n-3 FA and n-6:n-3 ratio among CAM, FLX, and OLA, a comparable skin FA profile, immune, and inflammatory response was observed among treatments at a dose of 0.37 g oil/kg BW. Therefore, CAM may be a suitable alternative to FLX in equine diets for the delivery of ALA. The fatty acids (FA) linoleic acid (omega-6; LA) and α-linolenic acid (omega-3; ALA) must be supplied in the diet as they cannot be endogenously produced by horses. Camelina oil supplies a similar omega-6 to omega-3 ratio (approximately 1:2) as other ALA-rich oils such as flaxseed oil (approximately 1:4). Omega-3 FA can benefit skin health, immunity, and inflammation, but the effect of camelina oil on these parameters in horses has not been investigated. Therefore, the objective of this study was to determine the effects of camelina oil on skin health, immunity, and inflammation in horses compared to 2 commonly supplemented oils, canola and flaxseed. Horses were supplemented with one of 3 ALA-enriched oils (camelina, canola, or flaxseed) for 16 wk and the skin FA profile, immune, and inflammatory response of horses in each treatment was assessed and compared. Within 8 wk of supplementation, skin favored the incorporation of omega-3 FA in all treatments, with greater incorporation of eicosapentaenoic acid (EPA) in the skin of the flaxseed group at week 16. Immune and inflammatory responses were not different among treatments. Our results suggest that supplementation with ALA increases n-3 FA incorporation into the skin and camelina oil produces similar skin FA, immune, and inflammatory responses as canola and flaxseed oil.