RESUMEN
The present study was conducted to investigate the aqueous extracts of Azadirachta indica (AZN), Cnidoscolus angustidens (CNA), and their combination (MIX) at dosages of 0-, 0.6-, 1.2-, and 1.8- mL for their ability to reduce greenhouse gases and fermentation profiles in an in vitro study using horse feces and a nutrient-dense diet (as substrate). The quantity of greenhouse gas and fermentation profiles were determined in in vitro incubation for 48 h. Extracts of AZN, CNA, and MIX reduced total gas production of the incubated and degraded substrates in a dose-dependent and time-dependent manner. Production of CH4 was reduced (P < .05) by 4.41% to 54.54% with the incubated substrates and by 1.16% to 61.82% with the degraded substrates. However, AZN and MIX reduced (P < .05) CO by 4.43% to 12.85% with the incubated substrates and by 0.70% to 16.78% with the degraded substrates. In like manner, the plant extracts and combination reduced (P < .05) H2S production in a dose-dependent and time-dependent manner by 18.37% to 67.35% with the incubated substrates and by 8.51% to 67.23% with the degraded substrates. Extracts maintained pH within the normal range, reduced dry matter digestibility and metabolizable energy, and improved (P < .05) concentration of short chain fatty acids. Overall, aqueous extracts of AZN and CNA and their combinations had a positive effect on reducing the greenhouse gas production with no deleterious effect on fecal horses' fermentation activities.