The nutritive value of subterranean clover herbage grown under irrigation in northern Victoria

Abstract

A series of experiments is described which considered the nutritive value of subterranean clover (Trifolium subterraneum) herbage grown under irrigation in northern Victoria. Digestion studies were undertaken with sheep and dairy cows and the degradation of herbage samples in nylon bags was evaluated. Digestion coefficients were estimated, 1eaf:stem ratios were measured, mineral and amino acid profiles were obtained, and protein degradabilities were assessed. The digestibility and chemical composition of freshly cut subterranean clover herbage was relatively constant until wilting of the herbage in mid spring. With few exceptions, in vivo DM digestibility and nitrogen content were greater than 75% and 3.2%, respectively, and neutral detergent fibre, acid detergent fibre and lignin were less than 40%, 30% and 6%, respectively. The chemical composition of leaves and petioles/stems were very different. The digestibility of the leaf fraction was often much lower than that of petiole/stem, but its nitrogen content was higher. Reasons for this, and their implications, are discussed. Discussed also are the adequacy of herbage minerals and their solubilities. Rumen protein degradability for vegetative herbage ranged from 0.51 to 0.64. Of the plant components, the protein in stems was more degradable than the protein in leaves. The effects of incubation of herbage in nylon bags in the rumen for 24 h on amino acid composition are also discussed.