In Vitro Screening and Optimization of Organic and Inorganic ingredients for Methane Mitigation with Rumen Fermentation Efficiency

Abstract

ABSTRACT

GHG emission from ruminants contributes to environment, responsible for global warming and through diet modification enteric emission may be diminished. The present study aimed to evaluate and optimize the efficacy of selected organic (ORG) and inorganic (INORG) feed additives for mitigating enteric methane (CH₄) production while maintaining rumen fermentation efficiency under in vitro conditions. Two experiments were conducted using a total mixed ration (TMR) comprising berseem, wheat straw, and concentrate. In the first experiment, a completely randomized design (CRD) with a 5 × 4 factorial arrangement (five additives × four inclusion levels) was employed, while in the second experiment, a CRD was used to evaluate composite feed additive at graded inclusion levels (0.5%, 1.0%, 1.5%, and 2.0%) to assess synergistic effects. Five additives (INORG 1, INORG 2, INORG 3, ORG 1, and ORG 2) were initially assessed at 0.15%, 0.30%, and 0.60%. Results revealed that INORG 1 reduced methane production in a dose-dependent manner, with 0.15% identified as the optimal level balancing methane mitigation and digestibility. INORG 2 (0.60%) improved nutrient digestibility while reducing methane, whereas INORG 3 (0.30%) enhanced fermentation efficiency and reduced methane through propionate formation. ORG1 (0.60%) and ORG 2 (0.30%) effectively reduced methane without adversely affecting digestibility. In the composite study, CH₄ (%) showed a substantial reduction of approximately 37.7% at 1.5% inclusion, while maintaining acceptable digestibility and microbial efficiency. Although higher inclusion levels further reduced methane, they showed a declining trend in digestibility. Overall, the study demonstrates that optimized combination of organic and inorganic additives exerts a synergistic effect in mitigating CH₄ while sustaining rumen fermentation. The 1.5% composite feed additive was identified as the optimal level, offering a balanced approach for methane mitigation without compromising nutrient utilization, thereby providing a promising strategy for sustainable ruminant production. However, in vivo study to be conducted for validation of efficacy of the additive, while safety study in milk producing animals.

Keywords

Methane emission; In vitro gas production; Inorganic ingredients; Organic ingredients; Rumen fermentation; Electron sink; Composite Feed additives; Dose optimization