Effect of Azadirachta indica leaf extract on in vitro enteric gas production, protozoan, bacteria and methanogen populations in cattle rumen

Abstract

Several mitigation approaches including drugs, antibiotics, vaccines and chemical supplements have been adopted to mitigate methane emission from ruminants but found to be toxic to the host animal and sometimes expensive. This work studied the effect of methanolic extract of neem (Azadirachta indica) leaf as a cost effective and nontoxic supplement in cattle feed. The study determined the effect of increasing doses of neem leaf extract on bacterial, protozoa, methanogen population and total gas production in 24hrs of in vitro incubation. Treatments were designed to 9 doses of percentage methanolic extract of neem leaf (0, 10, 20, 30, 40, 50, 60, 70, and 80 %) supplemented to the cattle feed. Increased percentage of neem leaf extract resulted in significant (p ˂ 0.05) decreased in total gas production. The highest inhibitory effect was recorded at 60% neem extract which reduces total gas produced from 23. 47 mL/g DM to 4.23 mL/g DM. The least inhibitory effect at 10% neem extract reduces gas production to 20.43 mL/g DM. Increased percentages doses of neem leaf extract also resulted in significant decrease (p ˂ 0.05) in protozoa and methanogen counts as compared with the control. However, neem leaf extract at 10 – 20 % increased total bacteria count to 26. 67 × 10⁶ CFU/mL as compared to control (25.33 × 10⁶ CFU/mL) but increased percentage of neem leaf at 30% and above reduced total bacteria count as compared to the control. Therefore, this study shows that methanolic extract of neem leaf is a promising feed additive as rumen modifying agent. It has the potential to reduce enteric gas production and consequent emission from ruminants.