In situ rumen degradation characteristics of sixty cultivars of barley grain

Abstract

Our objectives were to determine the extent of genetic variability in the rate and extent of ruminal digestion among 60 cultivars of barley, and to evaluate the correlations between ruminal digestion characteristics and chemical composition and test weight of barley cultivars. Barley samples were ground through a 2-mm screen, and bags containing 1 g of ground grains were incubated in the rumen of three late-lactation Holstein cows with rumen cannulae for 0, 1, 2, 4, 8, 12, 16, and 24 h. The rate and extent of ruminal digestion were estimated. The insoluble DM fraction ranged from 33.4 to 56.4%, the degradable DM fraction ranged from 34.1 to 60.2%, and the rate of degradation of DM ranged from 0.200 h−1 to 0.624 h−1. Hulled barley cultivars had lower (P < 0.05) soluble and degradable fractions than hulless cultivars. The soluble fraction was positively correlated to starch content of barley cultivars (P = 0.01) and the degradable fraction was correlated to the test weight and CP content (P < 0.01). The observed variability in the ruminal digestion characteristics of barley cultivars indicates that genetic selection holds promise as a means of enhancing the nutritional quality of barley for ruminants. We also observed that 70% of the variation in digestibility could be explained by measures of bulk density, starch content, and kernel weight. Key words: Barley cultivars, in situ degradability