In Vitro Fermentation and Methane Production with Diets of Varying Roughage (Prosopis cineraria leaves) to Concentrate Ratio

The experiment was conducted to study the effect of varying concentrate levels in diets with Prosopis cineraria dry leaves on in-vitro fermentation characteristics and methane production. Three composite feed mixtures (CFM) were prepared using Prosopis cineraria (Khejri) dry leaves as roughage source and barley grain in ratio of 80: 20 (D₁), 60: 40 (D₂) and 40: 60 (D₃) respectively, along with 2% mineral mixture and 1% common salt. The in-vitro dry matter digestibility (IVDMD), metabolites and methane production were measured for 24 h fermentation. In-vitro experiment revealed that increasing concentrate levels improved (P<0.05) the IVDMD of diets, which ranged from 70.18 to 74.25% and remained highest in D₃. Total gas (ml/g DDM) and methane (g/kg DDM) production as well as ME (MJ/kg DM) production were increased (P<0.05) with increasing levels of concentrate in the diets. There was a non-significant decrease in the pH of fermentation medium on increasing concentrate levels in the diets. TCA-ppt protein was reduced (P<0.05) whereas NH₃N, TVFA and protozoa population increased (P<0.05) by increasing concentrate levels in the diets. It is concluded that increasing level of concentrate improved total gas and methane production along with IVDMD. Methane production was lowest in diets having more Prosopis cineraria dry leaves because of high content of tannins in it, which inhibits the production of methane and reduced the population of protozoa.