COMPARATIVE DIGESTION IN CATTLE AND SHEEP FED WHEAT SILAGE DIETS AT LOW AND HIGH INTAKES

Winter wheat (Triticum aestivum L.), harvested at late milk, early dou gh, and hard dough stages of maturity was ensiled for nutritive compar isons. Diets were adjusted to 13% CP with a soy protein concentrate an d fed to six ruminally fistulated growing steers and nine adult wether s in a repeated 3 x 3 Latin square design to study the effects of main tenance and ad libitum intakes on digestibility of different feed frac tions. At both intakes, digestion values for the steers were greater t han or equal to those for the sheep for all feed fractions except CP. Wethers achieved greater intake per unit of BW than steers during ad l ibitum intake. Voluntary OM intakes of steers only differed between th e milk stage diet and the dough stage diets. At low intake, the diets containing the more mature silage were more digestible. At high intake , the OM of diet containing the early dough stage silage was most dige stible. Increased intake caused a depression in digestibility of diffe rent feed fractions. The magnitude of the depression varied among diet s and fractions. Data indicated that the nutritive value of diets base d on whole crop wheat silage is affected by stage of maturity, animal species, and amount of intake. The assessment of the nutritive value o f diets based on whole crop wheat silage should therefore be made with the animal species and at the amount of intake for which the diets ar e intended.