Ruminal digestibility and fermentation characteristics in vitro of fenugreek and alfalfa hay combination with or without the inoculation of Neocallimastix sp. YAK11

Fermentation characteristics of 5 combinations of fenugreek (Trigonella foenum-graecum L., FH) and alfalfa (Medicago sativa L., AH) hay in ratios (FH:AH) ranging from 100:0 to 0:100 were studied in response to inocula of either rumen fluids (RF) or rumen fluids plus a fungal culture of Neocallimastix sp. YAK11 (RFF). For the RFF treatment, the forage combinations were anaerobically incubated with fungal culture and Menke's medium for the first 24 h and then incubated with the stratified rumen fluids for 72 h. The value of the in vitro dry matter disappearance did not differ between RF and RFF. Cumulative gas production (ml/g DM) was fitted to an exponential model: GPt = GPmax×(1 − e−c×time); the maximum gas production (GPmax) was lower in RFF than in RF (P<0.01), but the rate constant c showed no difference. Molar proportions of CO2, CH4, and H2 were similar in both treatments. The pH values were lower for RFF than RF (P<0.01). Concentrations of ammonia N and total volatile fatty acids (VFA) did not differ between RF and RFF. In VFA pattern, molar proportions of propionate and valerate did not differ between RF and RFF. Molar proportion of acetate was greater in RFF than in RF (P<0.05), while molar butyrate and branch-chained volatile fatty acids proportions were lower in RFF than RF (P<0.01). Fibrolytic activities of carboxymethyl cellulase, avicelase, ferulic acid esterase, and acetyl esterase were similar between RF and RFF, but xylanase activity was greater in RFF than in RF (P<0.01). Regardless of the ratios of FH to AH in the forage combinations, the fungal inoculation at the inclusion level used did not alter the in vitro digestibility, but increased the molar acetate proportion and decreased the molar proportions of butyrate, branch-chained volatile fatty acids and maximum gas production.