In vitro dietary analysis of tropical browses and pasture consumed by goats

Goat production is rapidly expanding in tropical arid and semi-arid regions, yet limited knowledge exists on the feed they consume. This study investigated the in vitro digestibility, volatile fatty acid (VFA) profile, and methane production of 17 browse and eight forage species consumed by goats in Australia (Experiment 1) and tested interactive effects of forages (Avena sativa and Chloris gayana (Reclaimer)) and browses (Owenia acidula and Eucalyptus coolabah) combined in ratios of 25:75, 50:50, and 75:25, respectively (Experiment 2). Among browses, O. acidula exhibited the most favourable fermentation profile with 53.29% digestibility, 90.64 mL of gas/g dry matter (DM), total VFA concentration of 86.81 mM, 14.41 mL methane/ g digested DM, and an acetate to propionate ratio (A:P) of 1.54. Among the forages, A. sativa demonstrated the greatest digestibility (64.25%), total gas (115.02 mL/g DM), and VFA (114.02 mM), and the lowest methane production (19.90 mL/ g digested DM; P < 0.001). The 75:25 and 50:50 combinations of A. sativa: O. acidula resulted in greater DM digestibility (62.75% and 60.72%) and total gas (99.03 and 98.41 mL/g DM), while reducing methane (10.11 and 11.08 mL/ g digested DM), and A:P (1.91 and 2.17), respectively (P < 0.001) highlighting them as promising candidates for silvopasture systems.