The Effect of CLA Supplementation on Fat Deposition and Lean Muscle Mass in Horses.

Fatty acids are utilized within the equine industry to increase the caloric density of a diet as well as replace soluble carbohydrates. Omega-3 fatty acids are the most commonly supplemented fatty acids due to their potential health benefits; however, palatability limitations have spurred an investigation into alternative fatty acids like conjugated linoleic acid (CLA). CLA has shown health benefits similar to that of omega-3s, but the effect of CLA on equine fat deposition and lean muscle mass has yet to be established. The purpose of this investigation was to evaluate the effects of supplementing elevated levels of CLA on both lean muscle mass and fat deposition in young growing horses. In phase I of this study, 10 Quarter horses were fed between 5.0% and 10.0% of the concentrate diet, increasing the supplementation level every 3 d to determine the maximum inclusion rate of CLA in horses. In phase II, 9 Quarter horses were separated into 2 treatment groups fed either a control diet of soybean oil or CLA (n = 4 and 5/group, respectively) for 12-wks with BW and sex evenly distributed across treatments. Diets were formulated to be isocaloric and isonitrogenous and each treatment was offered at 0.015% BW/d. Growth measurements were collected weekly; rump fat thickness (RFT), ribeye area (REA), and intermuscular fat (IMF) were measured on d 7, d 42, and d 84 of the feeding period. The MIXED procedure in SAS was used with repeated measures to detect differences in growth performance and ultrasound measurements. There were no differences in performance characteristics or fat content between treatment groups (P > 0.05). In order to account for initial differences between treatments (P < 0.05), REA between the 17^th and 18^th ribs (REA17) was run with d 7 as a covariate. Mean REA17 tended to be higher in CLA supplemented horses (P < 0.07) when compared to controls. These results suggest that in an equine model, CLA does not affect growth performance or fat deposition, but may increase lean muscle mass in young growing horses. Further studies examining these effects over longer supplementation periods or in obese or insulin-resistant horses may offer insight to potential benefits of CLA in the horse.