The effect of different levels of magnesium oxide with high purity on digestion-fermentation characteristics and methane emissions of a high-concentrate diet in the in vitro batch culture

Manipulation of ruminal fermentation can be considered as an optimization procedure for methane emissions. Although, magnesium oxide meet a large portion of the magnesium needed for ruminants, it has a proper buffering capacity and can alter the rumen fermentation pattern. In this study, the effect of a commercial magnesium oxide in the levels of 1, 2, 3 and 4% of a high-concentrate diet was investigated in an in vitro batch culture prepared from sheep's ruminal fluid. Some of fermentation and degradability parameters, methane emissions and gas production parameters were measured when the diet incubated to the culture medium. The pH of the culture medium was significantly increased compared to the control, but the total volatile fatty acids (TVFA) did not change when magnesium oxide was added to the culture medium. The lowest amount of ammonia nitrogen (23.26 mg/dL) was observed at 4% of magnesium oxide. The gas production parameters and methane emissions were significantly lower in the treatments containing magnesium oxide when compared to the control group. Although the partitioning factor (PF) and the microbial mass yield were not affected by the treatments, but the efficiency of microbial mass synthesis increased significantly in the treatments containing magnesium oxide. It seems that the use of magnesium oxide can improve the rumen fermentation pattern via enhance the efficiency of microbial mass synthesis; reduce methane yield and increase of organic matter degradability. Also, further studies are needed to determine the effects of magnesium sources according to in vivo conditions in the future.