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 two commonly used oils in the equine industry, OLA and FLX, in healthy adult horses. Twenty-four adult horses, from two separate herds, were enrolled in this experiment. The horses underwent a gradual 4-week fat acclimation period to sunflower oil (~0.28% ALA), then were supplemented with either CAM (~34.9% ALA), OLA (~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 weeks. 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 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.