Abstract:
The feeding value for cattle of Wynn cassia hay (Cassia rotundifolia cv. Wynn) was assessed by measurement of dry matter intake (DMI) and average liveweight daily gain (ADG) of yearling steers fed chaffed diets of native pasture hay (0.44% N) that included 0, 10, 25, 50, or 80% of cassia hay. The cassia hay was obtained after seed harvest and, so, was of relatively poor quality (1.10% N, 70% stem). For comparison, lucerne hay (Medicago sativa cv. Trifecta) (2.42% N) treatments were also fed with native pasture hay at the same dietary legume proportions. The experiment was conducted over an 80-day period. Cattle fed only native pasture had low DMI (2.9 kg/head.day) and ADG (0.012 kg/head). DMI increased curvilinearly and ADG increased linearly with the proportion of cassia in the diet. Both DMI and ADG were significantly (P<0.05) increased when 50% cassia was fed (to 5.24 kg/head.day and 0.210 kg/head, respectively), while only 25% lucerne was needed to obtain significant increases in both parameters (to 5.69 kg/head.day and 0.310 kg/head). The poorer response to increasing dietary legume measured with cassia diets was not unexpected given that it had been cut at a more mature stage of growth. However, when the responses were examined against a common index of feed quality (protein content), both legume hays gave similar responses. Despite its relatively poor quality, the cassia hay was readily eaten at levels up to 50% of the diet, and improved both DMI and ADG. Our results suggest that cassia successfully introduced into native pasture will improve the liveweight performance of grazing cattle.