Supplementation of rice straw with crop by-products. I. Legume straw supplementation

Abstract

The effect of legume straw supplements (mung bean, cowpea, pigeonpea, peanut and lucerne) on rice straw intakes and digestibility was evaluated in a series of experiments. In Experiment 1, three sheep were fed on each of the legume straws ad libitum. Intakes of the straws were significantly higher in sheep fed on mung bean straw and lucerne (36.2 and 39.8 g kg −1 BW day −1, respectively). Lowest intake (29.9 g kg −1 BW day −1) and digestibility (54.2%) were observed in sheep fed on pigeonpea. The rumen digestibility of leaf and stem fractions of the legume straws and that of rice straw was evaluated using the nylon bag technique in Experiment 2. Supplementation with legume straw significantly increased the rate of rice straw digestion. The digestibility coefficients of the leaf and stem fractions of mung bean straw and lucerne were very comparable, and were significantly greater than the corresponding fractions of the other straws. The leaf fraction of cowpea straw exhibited a very low rumen digestibility up to 24 h after incubation. Differences in rumen ammonia and sulphide concentrations could not explain the increased rate of rice straw digestion in animals fed on the various supplements. In Experiment 3, 30 sheep were offered one of six dietary treatments. Treatment 1 consisted of rice straw ad libitum sprayed with a urea solution. In Treatments 2–6, sheep were given 250 g day −1 of one of the legume straws plus rice straw ad libitum. Supplementation with legume straws significantly increased total DM intake (g kg −1 BW day −1) from 12.6 for the control rice straw diet to 18.9, 16.6, 16.5, 17.3 and 18.8 for sheep supplemented with mung bean, cowpea, pigeonpea straws and lucerne, respectively. The ability of the legume straw supplements to increase digestion of rice straw above that obtained by a urea/mineral supplement is discussed.