Effects of saponin on enteric methane emission and nutrient digestibility of ruminants: An in vivo meta-analysis

Abstract

Although saponin originated from plants has been used to control methanogenesis performed by archaea methanogens in the rumen, its effect has been inconsistent. The objective of this study was to evaluate the effect of dietary saponin on enteric methane emission and nutrient digestibility of ruminants across various studies by employing a meta-analysis method. A database was developed by integrating data from 17 studies that originated from 11 articles. Different ruminant species, i.e., both small and large ruminants were included in the database. Data on related in vitro studies were excluded. Papers should be based on in vivo studies only that simultaneously reported dietary saponin and methane emission. Treatments were divided into control (no saponin), low saponin (saponin level less than 0.5% DM) and high saponin (saponin level above 0.5% DM). The treatments were considered as fixed effects whereas various studies were considered as random effects in the statistical mixed model methodology. Results showed that dietary saponin decreased enteric methane emission of ruminants as compared to control (P<0.05), and this was true for both low and high levels of saponin. Interestingly, low level of dietary saponin increased dry matter digestibility, organic matter digestibility, neutral detergent fiber digestibility and acid detergent fiber digestibility in comparison to control (P<0.05). However, saponin at high administration level reduced these nutrient digestibility than that of control (P<0.05). In conclusion, saponin is effective to mitigate enteric methane emission from ruminants in vivo and enhances nutrient digestibility provided that the level use should not exceed 0.5% DM.