Evaluation of the feeding value of pasture legumes

Abstract

The distinction between nutritive value and feeding value of forages for animal production is an important one, since variation in voluntary feed intake accounts for a large proportion of the variation that is observed in the feeding value of forages, while nutritive value is largely independent of voluntary feed intake. Some of the limitations in using estimates of dry matter digestibility as indices of nutritive value, and some alternative approaches to evaluation of the feeding value of forages including pasture legumes are discussed. For example, an index can be calculated from production responses of grazing sheep which reflects differences among cultivars of subterranean clover, Trifolium subterraneum, in their feeding values, expressed in terms of efficiency of production of wool. The extent to which the amount of forage that an animal consumes falls short of the amount that the animal needs to consume to meet its capacity to use energy as the constraint to forage intake (FCC) has been quantified previously. Feeding value of forages and some biomechanical and chemical constraints to voluntary feed intake, including the presence of plant secondary compounds, are considered in this context.