Feeding to Reduce Oxidative Damage

Although they are necessary for many physiological functions, when produced in excess or without adequate resolution, free radicals may contribute to several equine diseases. For example, an 83% difference in protein carbonyls, a marker of oxidative damage to proteins, was noted in synovial fluid of horses with joint disease compared to non-diseased joints. In another instance, thiobarbituric reactive substances (TBARS), a marker of oxidatively damaged lipids, were reported as three times higher among ponies with chronic laminitis when compared to healthy counterparts. Horses with recurrent airway obstruction show a greater depletion of tracheal epithelial fluid antioxidant status following organic dust exposure as compared to healthy horses. Since oxidative stress is naturally associated with exercise in many animals, including the horse, attention must also be directed at the athletic horse. For instance, increased concentrations of TBARS have been detected in Thoroughbred race horses after a simulated race, and thoroughbreds in training have reportedly presented with a reduced endogenous antioxidant status when compared to an antioxidantsupplemented cohort. In fact, various measures of oxidative stress have been correlated with intense exercise in the horse. Free Radicals Can Damage Feeds Various fats in feeds are susceptible to oxidation and free radical production. Consumption of these rancid feeds could potentially induce oxidative stress within the body. Although omega-3 fatty acids are required for normal cellular function and are pivotal in moderating inflammation, they are highly susceptible to rancidity because of the multiple double bonds within their long carbon chain. Peroxide analysis is a common indicator of feed rancidity. With this in mind, an independent laboratory determined the peroxide concentration in an omega-3 and micronutrient supplement* as well as five commercial equine feeds also containing omega-3 fatty acids (Figure 1). While the level of rancidity in the commercial feeds ranged from 14 – 32 mEq/kg fat, peroxide levels were nearly undetectable in the omega-3 and micronutrient supplement (2.6 mEq/ kg fat). In fact, of all the compounds tested, only this supplement had a peroxide concentration within the acceptable and safe range for human consumption (<10 mEq/kg fat; no standards have been established for the horse).