Starch is an important dietary carbohydrate ingredient in ruminants' diets, and can influence rumen fermentation, microbiota, methanogenesis and fiber digestibility. Dietary starch can influence both ruminal pH and hydrogen (H₂).

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences investigated the hypothesis that increasing starch intake can inhibit fiber digestibility through decreasing ruminal pH, increasing dissolved H₂ (dH₂) concentration and altering microbiota in the rumen. The main findings of this study are as follows: 1) The results showed a positive correlation between dH₂ and dissolved methane (dCH₄) in the rumen, and including explanatory variables of dH₂ with diet greatly improved prediction accuracy of dCH₄ concentration. These results indicated that enhanced ruminal methanogenesis induced by increasing starch intake are possibly mediated through mechanisms involving changes in ruminal dH₂. To our knowledge, this is the first evidence to verify that dH₂, rather than pH, was the best predictor of dCH₄ concentration. 2) For fiber digestibility, we found a great positive correlation between ruminal pH and NDF or ADF digestibility, and including explanatory variables of pH with diet greatly improved prediction accuracy of NDF or ADF digestibility. It suggests that decreased fiber digestibility induced by increasing starch intake are possibly mediated through mechanisms involving changes in ruminal pH.

The research was supported by the project of Hunan Province (Grant No. 2020NK2066), National Natural Science Foundation of China (Grant No. 31922080) and CAS President's International Fellowship (Grant No. 2018VBA0031).

The study entitled "Associations of ruminal hydrogen and pH with fiber digestibility and microbiota composition induced by increasing starch intake in beef cattle" has been published in Animal Feed Science and Technology, more details could be found at https://doi.org/10.1016/j.anifeedsci.2021.114980.

Contact: Rong Wang

E-mail: rongwang@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences