USE OF NON-PROTEIN NITROGEN IN THE NUTRITION OF DAIRY COWS: METABOLISM, PRODUCTIVE PERFORMANCE AND MILK COMPOSITION

Abstract

The objective of this review is to address the rumen metabolism of nitrogen, the use of non-protein nitrogen (NNP) in feed for dairy cows, and also to discuss its effects on consumption, digestion, productive performance and composition of milk protein fractions. There is a great variety of compounds characterized as NNP. Among these, urea is highlighted by the low cost, availability, ease of use, and it is widely used in animal feed, especially in ruminants. Several factors influence the use of nitrogen by ruminant, among them, the protein:energy ratio, the concentration of nitrogen in the diet, supplementation of sulfur and the period of adaptation of the diet. Although the inclusion of non-protein nitrogen sources in the diet of dairy cows is common practice in dairy production systems, more studies are needed in order to have greater efficiency and optimization of the use of dietary nitrogen and reduce the losses to the environment.