Effects of dietary inclusion of African catfish waste silage and probiotics on in vitro rumen fermentation and methane emissions.

This study evaluated the effects of African catfish (Clarias gariepinus) waste silage (AS) supplemented with or without probiotics (PB; Lactiplantibacillus plantarum and Bacillus coagulans) on in vitro rumen fermentation characteristics and greenhouse gas emissions using two ruminal inocula derived from White Fulani bulls and Red Sokoto bucks. Four White Fulani bulls (400 ± 20 kg) and four Red Sokoto bucks (25 ± 5 kg) served as rumen inoculum donors. Experimental diets were formulated with varying levels of AS inclusion (0%, 8%, 14%, and 20%), with or without probiotics (0.2 mL/g of diet). The diet was mixed with rumen inoculum to undergo fermentation. Total gas emissions were measured at 2, 4, 6, 24, 26, 28, 30, and 48 h of fermentation using a manometer for total gas production and a portable gas detector for methane (CH₄), carbon monoxide (CO), and hydrogen sulfide (H₂S). The pH levels were assessed using a potentiometer, while fermentation characteristics were determined using standard formulae. The inclusion of AS and PB significantly (P < 0.01) increased gas production rates and short-chain fatty acid production. AS alone increased pH, while PB inclusion tended to reduce pH in bulls, likely due to enhanced fermentation acidification. Asymptotic CH₄ production decreased (P < 0.0001) with increasing AS levels and probiotic supplementation. While probiotic inclusion reduced CO emissions, AS had no effect. Higher AS levels significantly (P < 0.0001) reduced H₂S production, with probiotics yielding the lowest H₂S values in both inocula. Probiotic supplementation also enhanced (P < 0.0001) dry matter digestibility and metabolizable energy, with the highest values observed at 20% AS inclusion. In conclusion, the inclusion of African catfish waste silage and probiotics (L. plantarum and B. coagulans) in ruminant diets reduced greenhouse gas emissions while improving rumen fermentation characteristics.