Chemical composition, intake, apparent digestibility and nylon-bag disappearance of leaf and stem fractions from straw of four barley genotypes

Abstract

Four experiments examined the chemical composition, intake, dry matter (DDM) and organic matter (DOM) apparent digestibilities and rates of disappearance from nylon bags of hand-separated leaf and stem fractions of straw from four genotypes of barley: Arabi Abiad, Beecher, C63 and ER/Apam. In experiment 1, 900 g leaf from each genotype was offered to three or four wethers together with 200 g soya-bean meal (SBM), and in experiment 2 the leaf from the same four genotypes was offered ad libitum with 200 g SBM. In experiment 3, 500 g stem from Arabi Abiad and Beecher was offered with 100 g SBM to six wethers in two groups. Experiment 4 measured the rate and extent of disappearance of the leaf and stem fractions from nylon bags incubated in the rumen of wethers. The genotypes had widely contrasting morphological characteristics. Stems contained about half as much ash and crude protein as leaves and differences within fractions were small. The leaf and stem fractions of the two-rowed barleys Abiad and Apam contained less modified acid-detergent fibre than the six-rowed Beecher and C63 genotypes.

When leaf was offered with SBM, both restrictedly and ad libitum, the DDM and DOM of this fraction were similar between genotypes (P > 0·05) and in experiment 2 the intake of leaf was also similar between genotypes (P > 0·05). The apparent digestibility of stem differed significantly between Arabi Abiad and Beecher in experiment 3 (P < 0·05). Significant differences were apparent between genotypes in the extent and rate of disappearance of leaf and stem from nylon bags after 48 h incubation in the rumen.