Ruminant Protein Metabolism Characteristics
Cows are anti-animal and have a rumen that acts like a fermenter. Nitrogen-containing compounds that enter the anti-automated object include proteins, amino acids, and non-protein nitrogen compounds, which are degraded by microorganisms in the rumen and enzymes secreted by them or synthesized by rumen microorganisms. 60% to 80% of the feed protein is degraded in the rumen, and the remaining 20% to 40% directly enters the abomasum and small intestine. It can be seen that the protein of the ruminant is mainly derived from the microbial cell protein, and the nitrogen source required by the rumen microorganism may be derived from protein feed such as soybean meal, cotton aphid, etc., and may also be derived from non-protein nitrogen such as urea, ammonia, etc. Can meet the needs of nitrogen growth and reproduction of bacteria. Therefore, the conversion of dairy feed protein in the rumen can be divided into feed protein degradation and microbial protein synthesis.
1 degradation of feed protein in the rumen
When the rumen microorganisms are in contact with the feed protein, the proteolytic enzymes secreted by the rumen microorganisms and the peptidase hydrolyze the ingested protein into peptides and free amino acids, and some of these free amino acids can be directly utilized to synthesize microbial proteins or other components of the microorganisms. As the cell wall and nucleic acids, other amino acids continue to decompose to produce volatile fatty acids, carbon dioxide and ammonia. A portion of the ammonia is utilized by the microorganisms, but most of it diffuses into the liver through the rumen wall and is converted to urea. A portion of the urea is recycled to the rumen through dilution and diffusion of saliva and rumen, while other portions are excreted through the kidneys and lactation.
2 Synthesis of rumen microbial proteins
Rumen microorganisms synthesize microbial proteins using degradation products (peptides, amino acids, and ammonia) of feed proteins. NRC (1989) reported that microbial protein can provide 39% to 79% of the protein required for 45 kg of cows per day. Clark (1992) showed that 59% of dairy cow's chyme protein is microbial protein. This shows the importance of converting feed proteins into microbial proteins.
Some non-protein nitrogen compounds, such as urea, are not proteins, but provide a nitrogen source for the synthesis of rumen microbial proteins in ruminants, which in turn meets the host's need for protein. In the cancerous stomach of ruminants, a large number of microorganisms such as bacteria and ciliates are parasitic. The urea enzyme secreted by bacteria decomposes urea into ammonia (NH3) and carbon dioxide (CO2). Bacteria use ammonia as a raw material, and the compound decomposition product organic acid is used as an energy source. Five to six hours after the cows ate urea, the bacteria in the rumen increased several times. Ciliates eat a lot of bacteria and multiply them. Therefore, 10 to 16 hours after the cows eat the urea, the bacteria are drastically reduced, and the ciliates are soaring. A large number of bacteria and ciliates that have been propagated by urea enter the stomach and intestines, are killed by gastric juice, and are absorbed and utilized by cows as high-quality protein. Therefore, the rational addition of non-protein nitrogen in the cow's diet can reduce the amount of protein added, which can save the shortage of protein resources and greatly reduce production costs.