Rumen microorganisms can utilize non-protein nitrogen (NPN) such as ammonia to synthesis rumen microbial proteins for cattle and sheep. Urea is a cheap source of NPN but the hydrolysis rate of urea in the rumen is speedy and exceeds the ammonia utilisation rate of rumen microorganism. Surplus ammonia is harmful to the animal and is also associated with increased methane production. Coated urea is designed to provide a controlled release of urea in the rumen, allowing for a more efficient utilisation of nitrogen by rumen microbes.
In Figure 1, it is clearly shown that compared with Menogen plus (the coated urea), normal urea is almost completely degraded within 20 minutes. On the other hand, the degradation rate of soybean meal or canola meal is too slow. Within 8 hours, the degradation rate of soybean meal and canola meal is about 50% and 30%, respectively, considered as the good source of rumen undegraded protein.
However, less ammonia concentration may not provide sufficient nitrogen source for rumen microorganisms to effectively synthesise rumen microbial protein. Therefore, addition of the coated urea could provide stable nitrogen supply for rumen microbes. It is reported that providing 90 grams coated urea per day per cow could replace 450 grams soybean meal and increase milk production by 0.85 kg per day per cow.
Figure 1. The degradation rate of different nitrogen sources in Rumen
In summary, this controlled release urea can lead to several benefits in terms of methane reduction and overall animal nutrition:
- Reduced ammonia levels:
The coated urea undergoes gradual hydrolysis in the rumen, releasing ammonia at a controlled rate. This controlled ammonia release ensures a stable nitrogen supply for rumen microbes, reducing excess levels. High ammonia levels in the rumen are associated with increased methane production.
- Improved microbial protein synthesis:
The coated urea supports the growth of rumen microbes by providing a steady and controlled supply of ammonia. These microbes are responsible for breaking down fibrous materials and producing microbial protein. Efficient microbial protein synthesis can lead to improved feed digestion and reduce d methane emissions.
- Optimised nitrogen utilisation:
The coated urea allows for better synchronisation between available nitrogen and microbial needs. This synchronisation can lead to improved utilisation of dietary protein and reduced excretion of nitrogen in the form of urea. Lower nitrogen excretion can contribute to reduced ammonia levels and subsequently, reduced methane production.
- Balanced rumen environment:
The coated urea helps in maintaining a stable rumen PH and stable pH conditions are conductive to the growth of specific microbes that produce less methane during feed digestion.
- Increased fibre digestibility:
Improved microbial efficiency and balanced rumen pH can enhance the digestion of fibrous materials. Enhanced fibre digestion results in fewer substrates available for methane-producing microbes, leading to reduced methane emission.