humans. In human nutrition it has recently been recommended that rather than the ratio of n-6:n-3 in the diet, more emphasis should be placed on the actual amounts of the individual n-6 and n-3 fatty acids in the diet. Therefore, in horses, it may be more important to supplement the diet of horses with omega-3 fatty acids, as most individuals are likely to have enough omega-6 in their daily ration. Soy, corn, and sunflower oils are rich in omega-3, while linseed, flax, soy and canola are rich in omega-6. Fish oils (e.g. cod liver oil) are also rich sources of the omega-3 fatty acids.
Benefits of feeding oil
Studies have reported an improvement in athletic performance when oil is fed to horses as an energy source. It would appear that horses require between two to three months to completely adapt to oil-supplemented diets, although improvements in performance may be evident much earlier than this (3 to 5 weeks). Feeding horses oil instead of a starch-based feed has also been seen impact on behaviour in horses, with those fed oil as an energy source much less reactive and calmer than those fed the same amount of energy from starch.
Feeding oils can have health benefits; for example, there is increasing interest in human and animal nutrition in the potential benefits of omega-3 fatty acid supplementation (or alteration in the dietary n-6:n-3 ratio) on health. In horses, studies have demonstrated marked decreases in inflammatory responses in horses fed linseed oil and fish oil. Omega-3 fatty acid supplementation has also been seen to decrease inflammatory markers in arthritic horses, reduce indicators of pulmonary inflammation, and lower heart rate in exercising horses, which may delay the onset of fatigue. Omega-3 supplementation can also be beneficial for horses with allergies. Furthermore, supplemental n-3 has been associated with positive effects on fertility and foetal development in other species, while in the stallion n-3 FA supplementation has been seen to improve seminal characteristics. Moreover, n-3 balance may improve reproductive function in the mare. However, the physiological importance of these findings is still unclear and further research is required to determine the effects of omega-3 fatty acid supplementation on equine health.
Supplementary oils are well utilised by the horse with digestibility values of over 85 percent. However, the amount of oil that can be included in the ration is limited. Studies in other species have shown that oil can impact on fibre digestibility if fed in large amounts. In horses, the addition of oil at up to 15 percent of the total ration (DM basis) had no effect on fibre digestibility, whereas amounts above that have been seen to impact on the microbial populations in the large intestine. It is thought that horses have a limited capacity to digest oil in the small intestine and any undigested oil travels to the hindgut and has a negative impact on the microbes and consequently fibre digestion. The rate at which oil is introduced in to your horse’s diet is also important. Rapid introduction of oil-supplemented diets is associated with steatorrea (greasy faeces) and increased faecal output; again, an indication that the fat has escaped digestion in the small intestine. However, these adverse effects are generally avoided if fat is gradually introduced over a period of 4 to 14 days, depending on the level of fat supplementation.
Because oils are energy-dense there is a concern that feeding oil-supplemented diets can cause excess weight gain. Metabolic utilisation of absorbed fat is highly efficient in horses, and there is a greater conversion of the energy in oil compared to carbohydrate. Therefore, because oil is utilised by the horse for energy more efficiently than other sources of dietary energy, adding oil to the horse’s diet decreases the amount of dietary energy required for the same amount of activity. However, in horses that are less active or ‘easy-keepers’, feeding oil should be done in moderation and the animal’s