Abstract:

Abstract: This review summarized the research progress of feed additives in rumen fermentation in 2009. Ionophores, such as monensin alters volatile fatty acid (VFA) production in the rumen towards more propionate (Pr) production at the expense of acetate (Ac), which results in increased glucose availability to the animal through gluconeogenesis, decreases the production of methane by inhibiting H2-producing bacteria but not directly inhibiting methanogens. Ionophores decrease milk fat content by an incomplete biohydrogenation process of long-chain fatty acids in the rumen that interferes with de novo fat synthesis in the mammary gland. Adding fibrolytic enzymes and amylase to ruminants can improve the nutrient digestibility. Saponin decreases the production of methane by inhibiting rumen ciliate protozoa. The appearance and proliferation of tannin-tolerant bacterial species to enhance their tolerance to tannins and only condensed tannins extract influence the ruminal biohydrogenation. Essential oils reduce protein and starch degradation and an inhibition of amino acid degradation in rumen due to the selective action on certain rumen micro-organisms. DFM include yeast, lactic acid bacteria, Bacillus can increase in nutrient digestibility, alteration of the proportion of volatile fatty acids produced in the rumen, reduction in ruminal ammonia, and increase of ruminal microorganism population. But the beneficial effects of yeast products depend on lactation stage, diet characteristic and environmental condition.

Key words: Key words:ionophores; enzyme preparations; plant extract; direct-feeding microorganism; rumen fermentation modifiers