Different microbial genera drive methane emissions in beef cattle fed with two extreme diets

Feed additives for methane mitigation: Recommendations for testing enteric methane-mitigating feed additives in ruminant studies

There is a need for rigorous and scientifically-based testing standards for existing and new enteric methane mitigation technologies, including antimethanogenic feed additives (AMFA). The current review provides guidelines for conducting and analyzing data from experiments with ruminants intended to test the antimethanogenic and production effects of feed additives. Recommendations include study design and statistical analysis of the data, dietary effects, associative effect of AMFA with other mitigation strategies, appropriate methods for measuring methane emissions, production and physiological responses to AMFA, and their effects on animal health and product quality. Animal experiments should be planned based on clear hypotheses, and experimental designs must be chosen to best answer the scientific questions asked, with pre-experimental power analysis and robust post-experimental statistical analyses being important requisites. Long-term studies for evaluating AMFA are currently lacking and are highly needed. Experimental conditions should be representative of the production system of interest, so results and conclusions are applicable and practical. Methane-mitigating effects of AMFA may be combined with other mitigation strategies to explore additivity and synergism, as well as trade-offs, including relevant manure emissions, and these need to be studied in appropriately designed experiments. Methane emissions can be successfully measured, and efficacy of AMFA determined, using respiration chambers, the sulfur hexafluoride method, and the GreenFeed system. Other techniques, such as hood and face masks, can also be used in short-term studies, ensuring they do not significantly affect feed intake, feeding behavior, and animal production. For the success of an AMFA, it is critically important that representative animal production data are collected, analyzed, and reported. In addition, evaluating the effects of AMFA on nutrient digestibility, animal physiology, animal health and reproduction, product quality, and how AMFA interact with nutrient composition of the diet is necessary and should be conducted at various stages of the evaluation process. The authors emphasize that enteric methane mitigation claims should not be made until the efficacy of AMFA is confirmed in animal studies designed and conducted considering the guidelines provided herein.

Stabilization of microbial network by co-digestion of swine manure and organic wastes

The production of biogas from organic waste has attracted considerable interest as a solution to current energy and waste management challenges. This study explored the methane (CH4) production potential of swine manure (SM), food waste (FW), and tomato waste (TW) and the changes in the microbial community involved in the anaerobic digestion process. The results revealed that the CH4 production potentials of the four kinds of SM samples were influenced by the characteristics of SM (e.g., age and storage period). Among the four kinds of SM samples, the CH4 yield from the manure directly sampled from primiparous sows (SM3) was the highest. The CH4 yield was significantly improved when SM3 was co-digested with FW, but not with TW. The addition of SM fostered a stable CH4 production community by enhancing the interaction between methanogens and syntrophic bacteria. Furthermore, the addition of FW as a co-substrate may improve the functional redundancy structure of the methanogenesis-associated network. Overall, the characteristics of SM must be considered to achieve consistent CH4 yield efficiency from anaerobic digestion since CH4 production potentials of SM can be different. Also, the contribution of co-substrate to the synergistic relationship between methanogens and syntrophic bacteria can be considered when a co-substrate is selected in order to enhace CH4 yield from SM.