Research on in vitro fermentation characteristics of Chloris virgata at different growth stages

Three Liuyang black goats fitted with ruminal cannulas were used in this study. Various indices were evaluated including 72 h total cumulative gas production, 0, 2, 4, 6, 8, 10, 14, 24, 36, 48, 72 h methane yield, both degradation rate of dry matter and concentrations of volatile fatty acid profile and ammonia N of Chloris virgata at different growth stages in vitro fermentation after 72 h. The result showed that significant (P0.05) or highly significant (P0.01) differences existed in Ash, crude protein(CP), neutral detergent fiber (NDF)、acid detergent fiber (ADF) levels between different growth stages. Compositions of CP and ash decreased and levels of NDF and ADF increased with the maturity. The VF of total cumulative gas production, methane yield and 72 h dry matter disappearance rate decreased with harvests prolonged. The growth staged did not affect the VF of total cumulative gas production (P0.05) because VF of methane yield during turning green, jointing, earing, flowering and maturity stage were not significantly different although they were significantly higher than withering stage.The 72 h dry matter disappearance rate during maturity, withering stage was significantly lower than that in the former growth periods. The concentrations of ammonia N, volatile fatty acid and acetic acid decreased and increased followed by decreased again. According to the changes of nutrients and fermentation gas production characteristics in vitro, it’s recommended that C.virgata should be harvested at the stage between earing to flowering.