The Inclusion Effects of Indigofera zollingeriana in Oil Palm Fronds Based Diet on Rumen Fermentation Kinetics and Microbial Yields In Vitro

Abstract

Oil palm fronds (OPF) cannot be used as a single feed for ruminants because its low rumen degradability due to low crude protein (CP) and energy content. The aim of this study was to investigate the inclusion effect of indigofera into OPF ration on rumen fermentation kinetics and microbial biomass production. The OPF and indigofera were milled through a 1 mm screen. Samples from individual OPF and indigofera and their combinations of 0.75:0.25, 0.50:0.50 and 0.25:0.75 (DM basis) were accurately weighed (1.0 g ± 0.0010 fresh weight in total) directly into Duran bottles. Samples were incubated in buffered rumen fluid at 39 ⁰C for 72 h. Gas production was measured at 2, 4, 6, 8, 10, 12, 16, 24, 36, 48, 60 and 72 h post incubation. Cummulative gas volume (three duplicate runs) were fitted to the exponential equation y = a + b (1-e^-ct). At 8 h, microbial biomass (MBO) and microbial nitrogen (MN) were estimated. Data were subjected to ANOVA based on CRD, and data showing significance between treatment means (P ≤ 0.05) were separated with orthogonal polynomial contrasts. The contrasts used were linear (L), quadratic (Q), or deviated from both L and Q (Dev). Significance was accepted at P ≤ 0.01. There were highly significant effects (P<0.01) of feed mixtures on gas prodcution profiles and microbial yields in the rumen. Increasing indigofera levels in the diet increased (quadratic effect, P<0.01) the gas asymptote and fermentation rate of the mixtures. Both MBO and MN had also the quadratic effects for the mixtures of OPF and Indigofera where the highest microbial yield was found in the combination of 25% OPF + 75% indigofera. It can be concluded from the present experiment that the optimal combination of OPF and indigofera was 25% and 75%, respectively.