In vitro gas production, methane production and fermentation kinetics of concentrate diet containing incremental levels of sodium humate

The redox potentials of humic acids make it a veritable pathway to hydrogen consumption in the rumen that may be a strategy to mitigate methane production. This study assessed the fermentability indices and methane production of incremental levels of sodium humate by in vitro gas production technique. Five experimental diets containing sodium humate at 0, 5, 7.5 10 and 12.5 g/kg diet were formulated. Inoculum prepared was from rumen fluid of West African Dwarf (WAD) goats. Incubation period was 24 hours at 39°C. Fermentation kinetics, methane and rumen metabolites production were analysed using one-way analysis of variance as outlined in the GLM procedure of SAS. Results revealed a decrease (p < 0.05) in CH4, VFA, acetate, propionate, butyrate, hydrogen consumed via CH4/VFA pathway (HC), volume of gas from degradable fraction (A) and rate of gas constant (c) with addition of sodium humate in the diet up to 10 g/kg diet. There were increase (p < 0.05) in VFA, acetate, propionate, butyrate, HC, A and c at 12.5 g/kg diet humate inclusion. Also, hydrogen recovery (HR), metabolizeable energy (ME), adenosine triphosphate (ATP), microbial biomass, organic matter digestibility (OMD) and short chain fatty acids (SCFA) increased (p < 0.05) with incremental levels of sodium humate inclusion, but above 10 g/kg diet inclusion, ATP, MB, ME, OMD and SCFA were observed to decrease (p < 0.05). It was concluded that the impact of sodium humate in diet of goats is dose dependent and that supplementing the diet of WAD goats with sodium humate for up to 10 g/kg diet can effectively reduce methane production while also providing energy for rumen microbes and other metabolic activities of the animal