Enteric methanogenesis in ruminants is identified as one of the primary anthropogenic sources of total atmospheric methane. Recent evidence suggests that rumen methanogenesis is significantly suppressed by lovastatin. Nevertheless, it has not been reported whether the methane reduction by lovastatin depends on ruminant livestock type, nor has fiber degradability been examined. The current research aimed to analyze the in vitro effect of lovastatin on the major fermentation end-products, gas production (GP) kinetics, and fiber degradation of a forage-based diet using rumen inoculum from sheep, goats, and cows. The experiment was conducted as a 3 × 3 factorial arrangement of treatments (dose of lovastatin: 0, 80, and 160 mg/L and three inoculum sources) in a completely randomized design. The results suggested that lovastatin did not affect the GP kinetics parameters. The anti-methanogenic properties of lovastatin were variable depending on dose and inoculum source. Lovastatin demonstrated a superior methane-lowering effect in sheep rumen inoculum compared with goat and cow inocula. The total volatile fatty acid (VFA) production was unaffected by lovastatin, but changes in acetate and valerate proportions were registered. Remarkably, lovastatin decreased the NH3-N concentration with goat and sheep inocula and the in vitro neutral fiber detergent (NDF) degradation for all inoculum sources.

This work aimed to evaluate the lovastatin (Lv) production by solid-state fermentation (SSF) from selected crop residues, considering the post-fermented residues as feed supplements for ruminants. The SSF was performed with two substrates (wheat bran and oat straw) and two A. terreus strains (CDBB H-194 and CDBB H-1976). The Lv yield, proximate analysis, and organic compounds by GC–MS in the post-fermented residues were assessed. The combination of the CDBB H-194 strain with oat straw at 16 d of incubation time showed the highest Lv yield (23.8 mg/g DM fed) and the corresponding degradation efficiency of hemicellulose + cellulose was low to moderate (24.1%). The other three treatments showed final Lv concentrations in decreasing order of 9.1, 6.8, and 5.67 mg/g DM fed for the oat straw + CDBB H-1976, wheat bran + CDBB H-194, and wheat bran + CDBB H-1976, respectively. An analysis of variance of the 2² factorial experiment of Lv showed a strong significant interaction between the strain and substrate factors. The kinetic of Lv production adequately fitted a zero-order model in the four treatments. GC–MS analysis identified only a couple of compounds from the residues fermented by A. terreus CDBB H-194 (1,3-dipalmitin trimethylsilyl ether in the fermented oat straw and stearic acid hydrazide in the fermented wheat bran) that could negatively affect ruminal bacteria and fungi. Solid-state fermentation of oat straw with CDBB H-194 deserves further investigation due to its high yield of Lv; low dietary proportions of this post-fermented oat straw could be used as an Lv-carrier supplement for rumen methane mitigation.