Enhanced energy metabolism with only forage and no concentrate
A Swedish study used a method called proteomics to analyse metabolic changes in muscle in trotters in training when fed a forage-only diet compared to a 50:50 forage:concentrate diet. The forage-only diet consisted of early harvested energy rich haylage and the forage:concentrate diet consisted of late harvested haylage from the same ley. The concentrate consisted of mainly oats and soybean meal and both diets were supplemented with minerals and salt. The two diets, forage-only and forage:concentrate, provided the same daily energy and protein intake.
The results show that when the horses were fed only the early harvested haylage proteins (enzymes) involved in the aerobic energy metabolism in the mitochondria in muscle cells were up-regulated. In addition the enzyme pyruvate dehydrogenase complex, which is a key enzyme for high aerobic energy metabolism, was up-regulated when the horses were fed the forage-only diet. The expression of proteins which catalyse the oxidation of long-chain fatty acids in the mitochondria was also up-regulated when the horses were fed only forage and no concentrate. This show that feeding forage-only diets will enhance body lipid and aerobic glucose metabolism compared to a high starch diet (concentrate) and the metabolic changes arising in muscle resembles the effects of training.
This positive effect on horses’ energy metabolism is due to higher production of acetate in the hindgut when horses consume only forage, which stimulates aerobic metabolism to greater extent than a diet including starch (concentrate/cereals). Important to remember when feeding forage-only diets is that the forage has to cover the horses energy and protein requirements and therefore, especially for athletic horses, it should be harvested early and have high nutritional content. A forage-only diet also needs to be complemented with minerals and salt.
Most commercial concentrates are cereal based and therefore contain considerable amounts of starch. Horses’ limited ability to digest starch leads to problems with digestion when they are fed too high rations of cereal based concentrate. Feeding high rations of concentrate is associated with health risks such as gastric ulcers, different intestinal disorders (colic), and disturbances in the intestinal flora, rhabdomyolysis and behaviour disorders. There are now many and strong reasons, concerning both health and performance in horses, to adapt to feeding regimens better suited for horses’ physiology and natural feed choices.
Sara Muhonen, AgrD
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