Discuss the major sources and fate of the following substances in ruminant digestion

Question

1 propionic, ethanoic , and butanoic acid
2 methane
3 carbon dioxide
4 ammonia

Answer 1

1) Propionic, ethanoic, and butanoic acid: These are volatile fatty acids (VFAs) produced during the fermentation of carbohydrates by microorganisms in the rumen of ruminants. Carbohydrates from the animal's diet are broken down by microbes into VFAs, with propionic acid being the main VFA produced. These VFAs are important energy sources for the ruminant, providing up to 70% of their total energy needs. As VFAs are absorbed through the rumen wall, they are transported to the liver, where they are converted to glucose or used for energy production.

2) Methane: Methane is a byproduct of rumen fermentation and is mainly produced by methanogenic archaea. These microbes produce methane as they breakdown fiber, starch, and other organic matter in the rumen. Methane is released by the animal through eructation (belching). Methane production in ruminants is a significant source of greenhouse gas emissions, contributing to global warming. It is estimated that ruminants contribute around 20% of total methane emissions worldwide.

3) Carbon dioxide: Carbon dioxide (CO2) is mainly produced as a result of fermentation processes in the rumen. Some CO2 is also produced through the animal's own respiration. CO2 is dissolved in the rumen fluid and can be absorbed and transported to the lungs for excretion. However, most of the CO2 produced in the rumen is eructated along with methane during the belching process.

4) Ammonia: Ammonia (NH3) is produced during the microbial breakdown of dietary protein in the rumen. Proteins are initially broken down into amino acids, and then further deaminated by rumen microorganisms, releasing ammonia as a byproduct. Ammonia is a source of nitrogen for the ruminant and is assimilated by the ruminal wall and metabolized by the liver into urea. Some ammonia can also be absorbed and utilized by microbes in the rumen for their own growth and protein synthesis.