Feeding value of subterranean clover, lucerne, phalaris and Wimmera ryegrass for lambs

Abstract

The feeding values of subterranean clover, lucerne, phalaris and Wimmera ryegrass were measured in three experiments using weaned lambs. With dried herbage, the voluntary intake of each species increased linearly with organic matter digestibility over the range tested (57-83%). Regressions for the two grasses did not differ from each other, nor did those for the two legumes; a common regression for the legumes had the same slope as that for the grasses but dry matter intake was about 190 g/d greater on legume diets. Digestibility accounted for 50 and 68% of variation in intake of legumes and grasses, respectively, but when cellulose concentration in the diet was used as the predictor, a single regression satisfied all the data and accounted for 76% of variation in intake. Energy retention by weaned lambs offered diets of dried subterranean clover or lucerne was 53% greater than that by lambs receiving the same intake of metabolizable energy from phalaris. When the intake of the two legume diets was unrestricted, this difference increased to 128%. Despite the 30% higher voluntary intake of the legume diets, the weight of digesta in the reticula-rumen at the end of a meal was the same as it was for the phalaris diet. When all four species were compared in the field, with herbage amply available, lambs grazing the two legumes retained 57% more energy than those on the grasses during the main spring period when the species were of comparable digestibility. As there was little or no difference, under the conditions of this experiment, in the intake of food from the four swards, it is concluded that the difference in feeding value resulted from more efficient use of metabolizable energy. Overall, subterranean clover had as high a feeding value for lambs as lucerne, and phalaris was not inferior to Wimmera ryegrass.