Ferulic Acid and Clinoptilolite Affect In Vitro Rumen Fermentation Characteristics and Bacterial Abundance

This study evaluated the effects of clinoptilolite (CTL) and ferulic acid (FA) supplementation on in vitro ruminal fermentation characteristics, gas production, and bacterial abundance. Treatments were arranged in a 2 × 2 factorial design (FA: 0 or 300 ppm; CTL: 0 or 1%) with repeated measures over time (2, 4, 8, 12, 24, 36, 48, and 72 h). Throughout the incubation period, the CTL and FAZ treatments recorded the highest pH values (<i>p</i> ≤ 0.05), maintaining levels closest to neutrality after 72 h. After 48 and 72 h, FA and CTL decreased (<i>p</i> ≤ 0.05) the ammonia concentrations while increasing (<i>p</i> ≤ 0.05) acetate and propionate. The methane, butyrate, and iso-VFA concentrations were unaffected (<i>p</i> > 0.05) by any treatment. FA increased the total gas production throughout the experimental period (<i>p</i> ≤ 0.05). Additionally, FA and CTL significantly reduced the relative abundance of <i>Ruminococcus albus</i> and <i>Streptococcus bovis</i> (<i>p</i> ≤ 0.05), while no significant effects were observed for <i>Selenomonas ruminantium</i> (<i>p</i> > 0.05). These findings suggest that both additives can positively modify the rumen fermentation characteristics and microbial composition, which could significantly contribute to animal nutrition by providing a promising strategy for enhancing rumen fermentation.