Utilization by ruminants of poor quality hay supplemented with different nitrogen and carbohydrate sources
Two experiments were conducted to study the utilization of poor quality hay by ruminants. In the first experiment, several nitrogen supplements were compared under practical conditions when fed to stocker cattle receiving a hay diet. Sixty cattle were wintered on fescue hay with one of five supplements: 1) none, 2) liquid urea-molasses supplement injected into the bales, 3) liquid-supplement self-fed in lick-tank, 4) mixture of deep-stacked broiler litter and ground corn grain and 5) soybean meal. Preliminary observations showed that the liquid supplement injected into bales was poorly distributed. Highest daily weight gains were for the animals supplemented with urea-molasses self-fed, litter or soybean meal. Compensatory gains under spring-grazing conditions subsequently suppressed these differences. Feed intake was low for all treatments. Feed efficiency was best for the soybean-meal group but feed cost per unit of gain was lowest for the broiler litter supplemented group. In a second experiment, urea and carbohydrates were supplemented to a fescue hay diet fed to lambs cannulated at the rumen, abomasum and ileum. The treatment diets were: 1) hay, alone or supplemented with 2) urea, 3) urea and molasses and 4) urea and corn. Chromic oxide and Co-EDTA were used as markers. Urea supplementation improved N retention but did not affect DM, ADF and energy digestibilities. The extent and efficiency of rumen fermentations were low, with a high methane production. Supplementation did not significantly affect the partition of digestion of DM and N along the gastro-intestinal tract. ADF digestion in the large intestine was increased by urea supplementation. Mean retention time of food along the gastro-intestinal tract was similar among treatments.