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Twenty-four Australian cashmere goats (32-40 kg live-weight (LW)), held in separate metabolism cages, were used in an experiment with a 2x4 factorial arrangement of treatments to study the effects of supplements of the dried leaves (browse) from two species of fodder tree (Tipuana tipu, and Calliandra calothyrsus) at four different levels (0, 0.83, 1.66% LW and ad libitum) on voluntary intake and utilisation of a basal diet of barley straw (BS). A supplement of urea-molasses (UM) (30 g urea, 70 g molasses) was given to control goats (0% browse), and both these goats and those given browse supplements consumed BS ad libitum. The basal diet of barley straw plus UM was consumed in limited amounts (41 g/kg(0.75) day) and was of low DM digestibility (47-53%). At the lowest level of Tipuana supplementation (0.83% LW, 27% DM intake), voluntary consumption of BS was significantly increased above basal, resulting in a 50% increase in total intake, and 73% in digestible DM intake. When Tipuana supplements were increased to 1.66% LW (56% DM intake), BS intakes decreased to the same extent that the supplement increased, resulting in no further improvement in either total intake or efficiency of diet use. When Tipuana was offered as the sole feed, total voluntary intake and digestible DM intake reached a maximum (66.4 and 42.0 g/kg(0.75) per day, respectively), and from a consideration of all aspects of this evaluation, Tipuana tipu compared very favourably with other high-quality browse species. However, Calliandra calothyrus proved to be of less value. The lowest level of supplementation resulted in a small increase in total (18%) and digestible DM (19%) intakes, but a decreased digestibility and availability of N for absorption and use. Further increases in supplement increased digestible intake, but N availability remained low and limiting. When Calliandra was offered as the sole diet ad libitum, total and digestible DM intakes (45.6 and 21.6 g/kg(0.75) per day) were no better than the control (barley straw plus UM) diet (41.5 and 22.0 g/kg(0.75) per day) and may be characterised as low in nutritive value and, in comparison with other browse species, of limited value as either a supplement or sole feed for ruminants in the tropics. (C) 2000 Elsevier Science B.V. All rights reserved. |
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