About this Research Topic
Microbial metabolism in the rumen leads to both desirable and undesirable products. Volatile fatty acids are the main source of energy and carbon for the ruminant animal, and the main source of glucose in case of propionate. The profile of volatile fatty acids absorbed from the rumen is also important to voluntary intake and energy partition. Fermentation intermediates serve as carbon skeletons where ammonia can be incorporated and amino acids synthesised, and absorbed and used by the host animal. Also, the content of some nutritionally desirable long chain fatty acids in meat and milk is strongly influenced by rumen fatty acids metabolism. On the other hand, methane formation in the rumen is wasteful in terms of energy and also contributes to climate change. Also, excess rate of ammonia release results in much nitrogen voided to the environment in urea, a process that is energy-costly and environmentally damaging. Therefore, it is an objective of applied rumen microbiology to intervene fermentation pathways and enhance the output of desirable products and decrease those products that are inefficient to production and harmful to the environment.
Research on manipulation of ruminal fermentation pathways needs both of basic science to understand the system, and applied science on strategies to manipulate fermentation. Central to basic understanding of rumen energetic metabolism is gaining insights on the control of metabolic hydrogen flows. With regard to nitrogen metabolism, the efficiency of nitrogen utilisation in the rumen is affected by catabolism of nitrogen compounds (proteolysis and amino acids fermentation), incorporation of nitrogen into microbial biomass, and intrarumen nitrogen recycling. With respect to the rumen outflow of long chain fatty acids, much progress has been made recently in elucidating the various steps of the complex process of biohydrogenation. The continuity of the advances in these areas is supported by molecular biology and –omics techniques, empirical and mechanistic modelling, as well as more classical biochemical/analytical, and in vitro cultivation techniques and in vivo animal experiments. Comparative gut microbiology also has much potential to help understanding microbial ecology and flows of metabolites.
We welcome contributions based on the above described or other approaches, or integrations of them, to answer questions like: i) How is the profile of end products of fermentation controlled? ii) What limits microbial growth in the rumen? iii) What is the impact of intra-rumen nitrogen recycling on the ruminant energy and nitrogen economy and what can be done to ameliorate it? iv) What do we need to know to better predict and manipulate fatty acids biohydrogenation? We would like to emphasise an approach that narrows down what needs to be elucidated and explicits future research hypotheses. Original research, reviews and mini-reviews, perspectives, and hypothesis and theory manuscripts are all welcome.
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