Role of Exogenous Enzymes in Feed Digestibility and Reducing the Emission Intensity of Enteric Methane Production in Ruminants

Several ruminant production systems depend on forage as a major source of nutritional constituents. The presence of diversified microflora in the rumen helps ruminants to adapt to a variety of ecological niches, as the microbes were synthesizing and secreting fibrolytic enzyme complex in order to hydrolyze plant fiber. Exogenous cellulases, hemicellulases, xylanase, and pectinases are used in ruminant feed biotechnology to enhance feed utilization, improve digestibility of certain feed components, and increase milk or meat production. At the initial stage of evlauation of these enzymes, in vitro gas production is used as an indication of feed fermentation. Indeed, the degradation of the substrate in the rumen is directly and positively correlated with gas production, and thus in vitro gas production techniques was utilised widely to determine the effect of supplemenation of exogenious enzyme on feed degradation. Nevertheless, in vitro gas production can also be used to estimate the methane emission potential in forges and feedstuffs. The mixture of exogenous enzymes affects the rumen fermentation characteristics, increase volatile fatty acid production and improves the nutrients supply, which can be used to support animal production and eventually reduce the enteric methane per unit of products in ruminants. This chapter highlights the effect of exogenous enzymes on the digestibility of high forage total mixed ration, research techniques used to quanity their effect and also their ability to indirectly mitigate in vitro methane production in livestock by reducing the intensity of methane emission per unit product.