Voluntary intake, apparent digestibility and prediction of methane production by rumen stoichiometry in sheep fed pods of tropical legumes

Foliages and pods of tropical legumes are alternative feeds for sheep which may contribute to improvement of their productive performance, and secondary metabolites such as tannins and saponins in the pods of Acacia pennatula and Enterolobium cyclocarpum may contribute to reducing methane production in the rumen. Rumen stoichiometry is a method by which methane production can be estimated. Our aim was to determine feed intake, apparent digestibility and methane production in hair sheep fed ground pods of two tropical legumes. Twelve male Pelibuey hair sheep were used in a completely randomized design with three treatments being: (1) control [commercial concentrate], (2) A. pennatula: substitution of 0.45 of ration dry matter (DM) with ground pods of A. pennatula and (3) E. cyclocarpum: substitution of 0.45 of ration DM with ground pods of E. cyclocarpum. There were no differences in DM intake between rations containing pods of legumes (1155 and 1122 g/d for A. pennatula and E. cyclocarpum, respectively), although there were differences (P<0.05) in DM intake between A. pennatula and control (933 g/d). Digestible organic matter intake did not differ among treatments, being 698, 737 and 730 g/d for control, A. pennatula and E. cyclocarpum, respectively. Apparent DM digestibility differed (P<0.05), with the control having the highest digestibility (0.84) relative to A. pennatula and E. cyclocarpum. There was no difference (P>0.05) in conversion efficiency of hexose to volatile fatty acids in the rumen with the control treatment which showed the highest efficiency (0.79), followed by E. cyclocarpum and A. pennatula (0.76). Energy loss as methane (kJ/mol) was not different (P>0.05) among treatments, with the control showing the lowest loss (195.7), followed by E. cyclocarpum (219.2) and A. pennatula (236.6). Further research is required to evaluate effects of the tannins and saponins in the pods of tropical legumes on rumen methanogenesis under practical sheep farming conditions.