Discuss the major sources and fate of the following substances in ruminant digestion
i.
Propionic, ethanoic and butanoic acid
ii.
Methane
iii.
Carbon dioxide
iv.
Ammonia
in details
i. Propionic, ethanoic, and butanoic acid:
These organic acids are primarily produced through the fermentation of carbohydrates by rumen microorganisms. Propionic acid is mainly produced during the fermentation of sugars, while ethanoic and butanoic acids are produced during the fermentation of starches and cellulose. These acids play a crucial role in energy metabolism in ruminants as they can be used as substrates for gluconeogenesis in the liver.
The fate of propionic, ethanoic, and butanoic acids in ruminant digestion involves their absorption across the rumen wall and further metabolism in the liver. Once absorbed, propionic acid is metabolized in the liver to produce glucose, which is used as an energy source by the animal. Ethanoic and butanoic acids are also converted into other metabolites, such as ketone bodies, which can be further metabolized for energy production.
ii. Methane:
Methane is produced as a byproduct of the fermentation of carbohydrates by rumen microorganisms, specifically by methanogenic archaea. It is generated in the rumen through a process called enteric fermentation, where carbon dioxide and hydrogen produced during fermentation are converted into methane by methanogenic archaea.
The fate of methane in ruminant digestion involves its release into the atmosphere through belching (eructation). Methane is a potent greenhouse gas and contributes to global warming. Strategies to mitigate methane emissions from ruminants include dietary interventions, such as adding plant secondary compounds or using feed additives that inhibit methanogenesis.
iii. Carbon dioxide:
Carbon dioxide is produced during the fermentation of carbohydrates in the rumen and is also a byproduct of methane production by methanogenic archaea. It can also be produced through the oxidation of organic matter by rumen microorganisms. Additionally, carbon dioxide can be generated in the rumen through the breakdown of carbonates in the feed.
The fate of carbon dioxide in ruminant digestion involves its absorption across the rumen wall and its release into the bloodstream. It can then be transported to the lungs and exhaled into the atmosphere. Some carbon dioxide may also be used in the process of gluconeogenesis in the liver.
iv. Ammonia:
Ammonia is produced in the rumen through the microbial breakdown of dietary proteins and urea. It is an important source of nitrogen for rumen microorganisms and can be used for microbial protein synthesis. However, excess levels of rumen ammonia can be toxic to the animal.
The fate of ammonia in ruminant digestion involves its absorption across the rumen wall and its conversion into urea in the liver. Urea is then excreted in the urine or recycled back to the rumen to provide a source of nitrogen for microbial protein synthesis. Excess ammonia can also be converted into microbial protein or absorbed into the bloodstream and excreted by the kidneys.