Herbage quality in Rhodes grass (Chloris gayana Kunth). 2. Intra-variety variation in yield and digestibility of plants of similar heading date.

Abstract

20 clones of similar heading date and selected from within Rhodes grass cv. Masaba were assessed at 3, 6 and 9 wk of regrowth. Lengthening the period of regrowth increased yield of DM and yield of DOM, but decreased digestibility in vitro of leaf, stem and whole-sward samples and leaf:stem ratios. Clonal effects were also significant for these characters except for leaf digestibility and leaf:stem ratio. No significant clone X regrowth period interactions were observed. Stem and leaf digestibility fell by 0.20 and 0.17 units daily, resp., while leaf:stem ratio dropped to 1.1 at 9 wk regrowth which coincided with initial heading. At this stage whole sward digestibility had fallen to 53, at a rate of 0.22/day. Leaf digestibility was always higher than that of stem. Clones differed significantly in digestibility showing a 5-unit range which had no relation to leaf:stem ratios. The 7 clones best in digestibility were among the 9 lowest in herbage yield. The ranking for yield of DOM did not differ from that for yield of DM, which showed a range of 1.38-2.45 t/ha. It is concluded that potential genetic gain in digestibility and leaf:stem ratio is offset by a corresponding decline in herbage yield. (Abstract retrieved from CAB Abstracts by CABI’s permission)