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Humic substances reduce ruminal methane production and increase the efficiency of microbial protein synthesis in vitro

Sheng, Ping, Ribeiro, Gabriel O, Wang, Yuxi, McAllister, Tim A
Journal of the science of food and agriculture 2019 v.99 no.5 pp. 2152-2157
acetates, ammonium nitrogen, climate change, dry matter digestibility, energy, greenhouse gases, humic substances, livestock nutrition, methane, methane production, neutral detergent fiber, rumen fermentation, ruminants, starch
BACKGROUND: In ruminants, enteric CH₄ represents a major energy loss for the host and is a potent greenhouse gas that contributes to climate change. Previous studies have shown that humic substances (HS) may have beneficial effects on livestock nutrition. The present study investigated the effects of HS on in vitro CH₄ production and rumen fermentation. RESULTS: Total gas production was linearly increased with increasing HS after 12 h of incubation, although it was unaffected after 24 and 48 h. Increasing HS linearly decreased CH₄ at all time points. Increasing HS linearly decreased NH₃‐N concentration and the molar proportion of acetate at 12 h, whereas the efficiency of microbial protein (MP) production and total dry matter digestibility (TDMD) linearly increased, with starch digestion (SD) responding quadratically. After 48 h, HS linearly increased MP and TDMD, with neutral detergent fibre digestibility responding quadratically. CONCLUSION: Inclusion of HS effectively reduced CH₄ production and increased substrate disappearance and the efficiency of microbial protein synthesis in vitro. However, its effect on in vivo CH₄ production, rumen fermentation and ruminant production requires further investigation. © 2018 Society of Chemical Industry