The only essential amino acid that has a requirement listed in the National Research Council's "Nutrient Requirements of Horses" is lysine. For an adult horse of mature body weight of 500 kg (1,100 lb), the range listed is 23.3 to 31 g of lysine per day. Protein sources with high lysine concentrations include legume forages, soybean meal, and fish meal. Corn by-product protein supplements like distillers dried grains, corn gluten meal, and brewers grains contain only about a third or less the concentration of lysine found in soybean meal. Luckily, mature horses like yours can generally meet their lysine requirement by consuming good-quality forage, grass forage included, as long as it is harvested at a fairly early stage of maturity and has been well fertilized, etc. If the forage is overly mature, stemmy, and lacking leaves, then a grain mix with soybean meal as the primary protein supplement can be added to the diet.

Browse related Faqs by tag: horses, aminoacids, lysine