EFFECTS OF GROWTH STAGE AND SWARD STRUCTURE OF MACROPTILIUM-LATHYROIDES AND M-ATROPURPUREUM ON SELECTIVE GRAZING AND BITE SIZE IN GOATS

This study was conducted to investigate the effects of growth stage (2 6, 49, 63, 78 and 106 days of regrowth) and sward structure of phasey bean (Macroptilium lathyroides) and siratro (M. atropurpureum) on sele ctive grazing and bite size of oesophageal fistulated goats. The selec tively grazed parts of phasey bean and siratro had higher levels of le af, crude protein, in vitro dry matter digestibility (IVDMD) and diges tible energy (DE) and lower levels of cell wall components than the re sidual forage. There was more selection when grazing phasey bean than siratro. As plants matured, leaf percentage of the grazed phasey bean decreased but changes in siratro were small. Goats grazing phasey bean had the largest bite size when grazing the 106 day regrowth, whereas animals grazing siratro had the largest bite size when grazing the 63 day regrowth. Bite size of goats grazing phasey bean and siratro was p ositively correlated with sward height, stem length and dry matter yie ld, and a higher correlation was found for phasey bean than for siratr o. However, the relation between the leaf percentage in the grazed lay er of the sward and bite size was inconsistent between the two legumes .