Efficiency of nitrogen use for dairy cattle

Abstract

The objective of this review is to address the metabolism of nitrogen (N), the use of different sources of N protein and non-protein in diets of dairy cows and discuss their effects on intake, digestibility, ruminal environment, productive performance, milk composition and especially on the N use efficiency (NUE). Ruminants have low NUE. This low efficiency has implications not only in economic and productive efficiency, but also in the emission of contaminants into the environment. Several factors influence the nitrogen utilization by ruminants, including the source of nitrogen and its concentration in the diet, the protein:energy rate, mineral supplementation, the total ration and diet adjustment period. NUE can be directly improved, understanding and modifying key processes regulating the NUE, including capture of N in the rumen, protein degradation, digestion and absorption in the gastrointestinal tract and use of amino acids (AA). This understanding of the processes involving the use of N by the ruminant, enables the development of strategies to manipulate or regulate the supply of AA for microorganisms to the animal and the mammary gland, ensuring greater efficiency, reconciled to a lower excretion nitrogen to the environment.