PREDICTION OF THE NUTRITIVE VALUE OF ALFALFA (SARANAC), BROMEGRASS (SARATOGA) AND TIMOTHY (CHAMP, CLIMAX, BOUNTY) FED AS HAY TO GROWING SHEEP

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Abstract
Forty-five male sheep (31.6 kg average body weight) were used to determine the nutritive value of three cultivars of timothy, (Champ, Climax and Bounty), one of bromegrass (Saratoga) and one of alfalfa (Saranac) fed as hays. Daily dry matter intake of Bounty (76.7 g/kg0.75 per sheep) was similar to that of alfalfa and bromegrass (76.4 and 73.9 g/kg0.75, respectively) and higher (P < 0.01) that that of Champ and Climax (65.1 and 65.8 g/kg0.75, respectively). Apparent nutrient digestibility values were highest for bromegrass, with the exception of protein, nitrogen-free extract and lignin, which were more digestible for alfalfa than for the grasses. Saratoga bromegrass had the highest TDN values and supported the highest average daily weight gains. Protein digestibility was directly related to the crude protein content of the hays (r = 0.98, P < 0.01). The true digestibility of nitrogen was estimated to be 90.12% with a metabolic nitrogen excretion of 4.46 g of N/kg of dry matter intake. Digestibility of cell contents was also directly related to its percentage in the forages (r = 0.97, P < 0.01). Dry matter digestibility was predicted from cell wall components by a summative equation (r = 0.96, P < 0.01). Voluntary dry matter intake (g/kg0.75) was negatively correlated with "water retention capacity" (r = − 0.99, P < 0.01) and with "packed volume" values of the hays (r = − 0.93, P < 0.05). It is suggested that under certain circumstances, the physical characteristics of hays such as density and water retention capacity are factors that influence voluntary intake.