DIGESTIBILITY AND VOLUNTARY INTAKE OF FORAGES FED AS HAY OR WILTED SILAGE TO BEEF STEERS

Publisher Website
Google Scholar
Abstract
Thirty-six steers (334 kg avg body wt.) were used to study the nutritive value of alfalfa (cv. Saranac), timothy (cv. Climax) and a mixture of red clover-timothy-Kentucky bluegrass. For 2 wk, the forages were fed ad libitum as either hay or silage. Dry matter (DM) intake was measured during the second week. Digestibility was determined during the fourth week by total collection with DM intake limited to 90% of that obtained previously. DM intake was highest for alfalfa and lowest for the grass mixture (P < 0.05) but was not affected by the method of storage. Total digestible nutrient values were similar for all forages. DM intake was highly correlated with lignocellulose content (r = −0.97, P < 0.01). Digestible protein intake was estimated by an equation previously obtained with sheep (r = 0.94, P < 0.01). Dry matter and energy digestibilities were similar for all treatments. Protein digestibility of alfalfa (67.4%) was higher than for timothy and the grass mixture while the opposite was observed for crude fiber. Comparing silages to hays, silage digestibility of crude fiber was five units higher and that of protein three units lower (P < 0.05). Digestibility of cell constituents was highest for alfalfa and lowest for timothy (70.5% vs 60.9%). Cell wall digestibility was highest for timothy (59.5%) followed by the grass mixture (57.5%) and alfalfa (47.4%). True digestibility of nitrogen was estimated to be 82.7% with a metabolic excretion of 5.74 g of N/kg of DM intake. Summative equations could not predict DM digestibility accurately. Key words: Nutritive value, steer, hay, silage, forage digestibility