Effect Of Two Fiber Source Diets On Enteric Methane Emissions In Dairy Cows

The effects of Rice straw (RS group) and Corn silage+ Rice straw (MF group) ingested on rumen fermentation, milk performance and enteric methane emissions in dairy cows were studied in this experiment. This study contained two main parts:1) Using automatic in vitro batch incubation system to investigate the effects on feed degradation characteristics, ruminal fermentation and methane production; 2) Animal trail to investigate the effects on feed intake, total tract degradation, milk performance and enteric methane emissions in dairy cows.The dry matter degradation, profile of volatile fatty acid, total gas and methane production were determined after 48 h in vitro fermentation. Compared with RS group, MF substrate had significant lower pH, and higher dry matter degradation, production of total volatile fatty acid, gas volume and initial fractional rate of degradation. It could be concluded that the fiber from MF group was easier to degrade for ruminal microorganism than that from RS group. Furthermore, we also observed the higher molar proportion of propionate and lower ratio of acetate to propionate and methane production in MF group than RS group, indicated that the pathway of rumen fermentation should be through propionate production for the fibre from MF group, and methane generation was decreased as a result.We selected fourteen Holstein cows with similar body condition in mid and late lactation, and devided into two groups based on paired-wised milk yields parities and days in milk. After 21 d adaptation, we performed the digestion trial, collected rumen fluid arid milk, measured enteric methane emissions in dairy cows. In. comparison with the RS group, the DMI, GEI and NDFI were significantly lower for MF group. It indicated that fibre from silage corn had better palatability and easier degradation in dairy cows. Total solids, protein, fat content and production in milk were greater in MF group than RS group, indicating that fiber from MF group improved milk performance in dairy cows. Enteric methane emissions in terms of methane conversion factor and methane per unit of milk yields were significantly lower for MF group than RS group, indicating that fibre from corn silage helped to decrease methane emissions in dairy cows.