Indices of stress in exercising horses fed diets containing varying amounts of omega-6 and omega-3 polyunsaturated fatty acids

Abstract

Dietary omega-3 polyunsaturated fatty acids have shown substantial benefits in humans including lowered serum cholesterol, blood pressure and indices of stress. The caloric and extracaloric benefits of feeding fat supplemented diets to performance horses are well documented (Webb et al., 1987; Meyers et al., 1989; Julen et al., 1995). However, omega-3 polyunsaturated fatty acids have not been studied to any great extent. This study was conducted to determine the efficacy of feeding omega-3 fatty acids on indices of stress and serum cholesterol in horses. Nine three- and four-year old horses were assigned to diet treatments according to sex, age and athletic ability. Concentrate diets consisted of: control (A), fatsupplemented diet with corn oil (B) and fat-supplemented diet with extruded/expelled soybean oil (C; N-3). Overall, heart rates were lower in horses fed the fat-supplemented diets compared to the control diet. On reining and cutting exercise days, heart rates were lower (P<.05) in horses fed fat-supplemented diets vs. the control diet. There were no differences (P>.05) in heart rates during exercise on reining and cutting days between horses fed the two fat-supplemented diets. Recovery heart rates following the SET from the end of exercise to 60 minutes recovery (R), were significantly quicker in horses fed diet C. Plasma cortisol concentrations were lowest in horses fed the soy oil-supplemented diet and highest in horses fed the corn oil-supplemented diet. Across treatments, plasma cortisol concentrations during the SET rose due to the onset of exercise and remained significantly higher (P<.05) than baseline during the SET. Serum cholesterol concentrations were higher in horses fed corn oil-supplemented diets than in the control or the soy oil-supplemented diets. There was no significant change (P>.05) in body weight between horses consuming these three diets. However, when compared to consuming diets B and C the horses fed diet A had higher (P<.05) concentrate intakes. There was no significant difference in hay intake (P>.05) between horses consuming the three diets.