Herbage quality in Rhodes grass (Chloris gayana Kunth). 1. The effect of heading date on intra-variety variation in yield and digestibility in vitro.

Abstract

350 selected plants of Rhodes grass cv. Mbarara (early-heading), Masaba (medium-heading) and Pokot (late-heading) were examined for both seed and herbage yield characters, the latter at the stage of initial heading. Within each of these cv. a large variation occurred between individual spaced plants in seed and herbage yield, leaf:stem ratio and OM digestibility in vitro (D-vitro). However, this variation was secondary, as it was largely accounted for by a wide variation in heading date, ranging over more than or equal to 8 wk within a cv. There was a progressive decline in yield characters with every wk of delayed heading. Early-heading plants produced yields of pure germinating seed more than double those of late plants. At the initial-heading stage these plants also had a higher herbage yield, leaf:stem ratio and D-vitro, but a lower content of stem and dead leaf. D-vitro was on average 7.6 units higher in early plants than in plants heading 8 wk later, but the extremes varied as much as 17 units between some early and late. D-vitro of leaf, stem and whole-sward samples fell by 0.07, 0.12 and 0.14 units, resp., with every day of delayed heading. Leaf digestibility and DM content were higher than those of stems. At the initial-heading stage whole-sward digestibility and leaf:stem ratio were higher in Mbarara than in Masaba and Pokot, because Mbarara plants were on the whole earlier in heading. Of those plants, however, which had a common heading date in each of the 3 cv. i.e. which were sampled at the initial-heading stage and on the same day, digestibility and leaf:stem ratios of Masaba plants were above those of Mbarara and, in particular, those of Pokot. (Abstract retrieved from CAB Abstracts by CABI’s permission)