Protein and urea
The majority of forage eaten by cattle is broken down in the rumen, primarily by a range of microbes collectively known as ‘rumen bugs’. Nitrogen, energy and sulphur are required to maintain a healthy population of rumen bugs. These are the key ingredients of most protein supplements.
Protein supplements can be divided into two broad categories, rumen degraded protein (RDP) and undegraded dietary protein (UDP), also known as bypass protein. As the name suggests, RDP is broken down in the rumen. Bypass protein is digested in the abomasum (‘true’ stomach) and the small intestines.
Protein meals such as cottonseed meal and copra meal are common sources of RDP, bypass protein and energy. Urea contains no energy or bypass protein but when fed in conjunction with sulphur can be utilised by rumen bugs to improve digestion. Urea is commonly referred to as non-protein nitrogen (NPN).
Feeding urea can increase feed intake by up to 20%, resulting in significantly higher grazing pressure. Urea is usually fed as blocks, loose mixes or through water medicators.
Urea poisoning
Urea can be toxic to stock if fed too quickly. When feeding urea start with low, or even no, urea content to prevent gorging and subsequent urea poisoning. Gradually increase the urea content to a maximum of 30%. Symptoms of urea poisoning include:
- muscle twitching
- excessive salivation (drooling)
- bloat
- breathing difficulties (either rapid and shallow or deep and slow)
- death.
When feeding urea it is essential to protect the supplement from rain. Supplement troughs should also have drain holes. Blocks can trap water, leading to urea poisoning.