Bulk tank milk ureas are a useful tool when used in conjunction with milk proteins, cow condition score and herd production. Urea is the animal’s way of removing excess nitrogen from the system.
This is produced from the breakdown of protein in the rumen which is not being captured/utilised by rumen micro flora. Excess nitrogen is also produced when animals are losing weight or during the natural process of muscle repair.
Normal bulk tank urea levels run at between 200 and 350 mg/kg which may be expressed as 0.02 and 0.035. However we can see large variations across the year especially with diet changes such as the introduction of Spring grass.
Extremes in milk urea can be a problem. If they are too high then it is costing the animal a considerable amount of energy to excrete the excess, and may well mean that money is being wasted through excess protein supplementation. If urea is too low then it could be having an effect on rumen function, digestion of fibre leading to reduced intakes. It’s worth noting that herds with high maize inclusion and those running lower protein diets, comfortably maintain milk urea at 120 to 180 with no adverse affects.
When looking at milk urea the trend rather than an individual test is important and it is vital to look at other production indicators and run a ration check before making changes.