How Urea Can Be Part of The Solution to Reduce Diet Cost in Dairy Cows

Urea can be a cost-efficient ingredient in the dairy diet that partially replaces feed protein and reduces total ration costs. Ruminant animals such as, cattle and sheep make efficient use of diets that are poor in protein quality or content, compared to monogastric animals such as pigs. This is because the ruminal microbes can synthesize high quality protein, as well as utilize recycled urea nitrogen (N, from blood and saliva) that would otherwise be excreted in the urine.

For lactating dairy cows, dietary crude protein (CP) mainly functions as the source of supply for metabolizable protein for the animal to meet her maintenance and milk production requirements. In practice, a dietary CP of 18% is commonly fed to high producing cows in the Midwest. However, research has shown that there’s no difference in lactation performance for diets exceeding 16.7% CP. Overfeeding CP would result in an increase in waste N excretion to the environment, as well as a lower ROI since protein is normally the costliest feed ingredient in a dairy ration.

Due to its high N content (a protein equivalent of 292%) and lower cost relative to feed protein (such as amino acids and blood meal), urea has been used in ruminant diets as an economical N supplement, a partial replacement of feed protein for microbial growth, a ruminal fiber digestion and referred as a non-protein nitrogen (NPN) source. Milk urea and blood urea concentrations have been used to monitor and assess the dietary crude protein and N utilization efficiency in lactating cows. This is because urea is the primary form of excretory N in mammals, and blood urea concentration equilibrates rapidly throughout the animal body system.

However, caution must be taken to limit the amount of urea in diet so that it does not cause toxicity. Most cases of urea poisoning are due to either poor mixing of feed or errors in diet formulation, resulting in accidental over consumption of urea. Since urea is readily available (broken down into ammonia) and fully degradable in the rumen, the ruminal microbes might not be able to utilize ammonia-N in time before the unused ammonia is transported to the liver. The ammonia is then converted back to urea, and either recycled back to digestive tract or excreted out of the animal body in urine to avoid toxicity. For lactating cows, feed no more than 0.2 lb. of actual urea per head per day, and a maximum of 0.1 lb. for dry cows.

Origination offers feed grade urea in bags, totes and bulk. Let us be your trusted partner for all your feed ingredient needs. Please contact us for more information.

Fei Sun, PhD, PAS
Dairy Product Technical Manager, Origination LLC.
fsun@originationo2d.com
October 27, 2021