Digestion characteristics of dallis grass (Paspalum dilatatum, Poir) pastures during the grazing season

A digestion trial, with four wethers fitted with rumen cannulas, was carried out to assess the effect of inclusion of a warm season dallis grass (Paspalum dilatatum) on the nutritive value of pastures during spring, summer and autumn. The design was a split-plot with a 2×3 factorial arrangement. Dry matter digestibility (DMD), in vivo, was higher (P<0.05) in autumn than in spring and summer (720, 680 and 650 g kg−1 DM, respectively). Kinetics of rumen digestion was measured with the nylon bags technique. Summer pastures with dallis grass showed the lowest (P<0.05) digestible fraction of neutral detergent fibre (NDF). Season had a significant (P<0.05) effect on the effective degradation of cell-wall (EDCW) (494, 364 and 386 g kg−1 for autumn, spring and summer, respectively). The inclusion of dallis grass did not have significant effects (P>0.05) on water soluble nitrogen, potentially degradable N, available fraction of total N consumed and fractional rate of degradation of N, while season had a significant (P<0.05) effect on the same parameters. Effective degradability was higher (P<0.05) for pastures without dallis grass (722 versus 687 g kg−1) and also higher (P<0.05) in autumn (939 g kg−1) than in summer (665 g kg−1) and spring (549 g kg−1). Rumen pH was higher (P<0.05) for pastures without dallis grass (7.01 versus 6.66). It is concluded that there exists a distinct season effect on nutritive value of pastures and that the inclusion of dallis grass may improve the use of dietary nitrogen.