Enteric methane mitigation in sheep through leaves of selected tanniniferous tropical tree species

This study was carried out to investigate the effect of supplementation of three selected tanniniferous tropical tree leaves of Ficus benghalensis, Artocarpus heterophyllus and Azadirachta indica on enteric methane emission, rumen fermentation characteristics and protozoal population in 20 native Indian adult male sheep (Mandya). The experiment was conducted in randomized block design with four treatments of five animals each. The sheep in control group (CON) were fed on complete feed block (CFB) comprising finger millet straw and concentrate in the ratio of 60:40 (DM basis) without any inclusion of tropical tree leaves. Sheep in three test groups ie. FIC, ART and AZA were also fed complete feed block prepared from finger millet straw and concentrate in the same ratio (60:40) as control, but wheat bran in concentrate mixture of test groups was partially replaced (10 parts w/w) with selected tanniniferous tropical tree leaves of Ficus benghalensis, Artocarpus heterophyllus and Azadirachta indica, respectively. The condensed tannin intake in sheep between 7.15 and 10.8 g/kg dry matter intake via selected tanniniferous tropical tree leaves did not influence dry matter and digestibility. About 20-26% reduction (p < 0.05) in enteric methane emission is achievable simply through the supplementation of selected tree leaves in straw based diet. The reduction in protozoal numbers (p < 0.05) due to selected tropical leaves supplementation appeared as primary cause for the reduction in enteric methane emission. The study confirmed that entodinimorphs protozoa are more vulnerable to the condensed tannin supplementation. The study established that significant reduction in methane emission is feasible without affecting feed fermentation characteristics. However, studies in large productive (growing, lactating) ruminants are warranted in order to explore the persistency of ameliorative effect in long term and improvement in productive performance thereof.