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 dough, and hard dough stages of maturity was ensiled for nutritive comparisons. Diets were adjusted to 13% CP with a soy protein concentrate and fed to six ruminally fistulated growing steers and nine adult wethers in a repeated 3 x 3 Latin square design to study the effects of maintenance and ad libitum intakes on digestibility of different feed fractions. At both intakes, digestion values for the steers were greater than 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 libitum intake. Voluntary OM intakes of steers only differed between the 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 digestible. Increased intake caused a depression in digestibility of different feed fractions. The magnitude of the depression varied among diets and fractions. Data indicated that the nutritive value of diets based on whole crop wheat silage is affected by stage of maturity, animal species, and amount of intake. The assessment of the nutritive value of 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 are intended.