Effect of supplementation of bioactive rich tree leaves on nutrient utilization, growth performance, methane emission and fatty acid profile in finisher lambs fed energy dense diet

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To study the effect of supplementing bioactive rich tree foliages in energy dense diet on lamb production and tissue fatty acid profile, 24 weaner male lambs (∼90days old) were divided equally into 2 groups and fed complete feed blocks without (C) and with 6% Hardwickia binata (anjan tree) leaves (T). Feed blocks in both the groups consisted of 3.25% rumen bypass fat. Dry matter intake and plane of nutrition were comparable among the groups but digestibility of neutral and acid detergent fibre were lower (P<0.05) in T than C. Rumen fermentation attributes revealed higher (P<0.05) concentration and proportion of propionic acid and total volatile fatty acids in T compared to C. The metagenomic equivalent values of total methanogens and protozoa were lower (P<0.05) while, population of Butyrivibrio fibrisolvens was higher in T compared to C. Loss of metabolizable energy through methane was reduced by 4.6 percentage points in T than C which resulted in higher microbial nitrogen synthesis in T from methane mitigation. Subsequently, the average daily gain in lambs was improved by 5.9% in T compared to C. The fatty acid profile of Longissimus thoracis muscle revealed higher (P<0.05) C18:2c9t11 content in lambs of T group than C. Hence, from the present findings it can be concluded that inclusion of Hardwickia binata leaves at 6% level increased condensed and hydrolysable tannin content of the diet which modestly affected rumen fermentation resulting in reduced methane production and enhanced conjugated linoleic acid content in muscle tissue.