Modulating rumen fermentation and methane emissions in vitro with Terminalia tomentosa, Bauhinia variegata, and Butea monosperma forest tree leaves of Ajodhya hill areas, Purulia (India): a comparative study

Abstract

This study aimed to evaluate the effects of three unexplored forest legume tree leaves—Terminalia tomentosa Roxb., Bauhinia variegata L., and Butea monosperma Lam.—on in vitro rumen fermentation and methane production. These tree leaves, along with Leucaena leucocephala (used as a control), were collected from the Ajodhya Hills Forest areas in Purulia, West Bengal, India. Total mixed rations (TMRs) were prepared as a basal substrate, comprising a concentrate mixture (40%), maize fodder (30%), and paddy straw (30%). The experimental TMR substrates were formulated by incorporating the test tree leaves (T. tomentosa, B. variegata, and B. monosperma) at inclusion levels of 5.0%, 7.5% and 10.0%, while the control TMR included L. leucocephala at equivalent levels. In vitro analyses assessed nutrient degradability, fermentation parameters and methane production. All tree leaves exhibited crude protein content > 10%, total carbohydrate content > 65%, rumen undegradable protein < 16%, and neutral detergent fiber < 50%, contributing to in vitro true organic matter degradability exceeding 55% across all TMRs. The production of volatile fatty acids (acetate, propionate, and butyrate) and the nitrogen (N) fractions (total-N, ammonia-N etc.) in the in vitro fermentation bottles were within normal physiological ranges. Incorporating these tree leaves into the TMRs, particularly at up to 7.5% of the total diet, supported favourable rumen fermentation profiles in vitro. Notably, the TMR containing T. tomentosa leaves exhibited a promising methane-mitigating effect. However, further research is required to confirm the impact of these tree leaves on the production and reproductive performance of ruminant livestock.