Potential of Slow-Release Nitrogen in Ruminant Feeding

Protein is one of the expensive nutrients in ruminant diet. It has dual-faceted functions as being the source of nitrogen for rumen microbes as well as amino acids for the host ruminant, and hence it is an integral component of ruminant feeding. Ruminants are unique in their ability to utilize non-protein nitrogen (NPN) as nitrogen (N) source for the growth of microbes and microbial protein synthesis in the rumen, which in turn fulfills about 70–100% of protein requirements of ruminants. The NPN sources could partially substitute for true protein in the diet. The low-cost, high N content, and easy availability make urea as a feasible NPN supplement. And, effective utilization of NPN also requires a synchronization between N (ammonia) released from the hydrolysis of urea and available fermentable energy in the rumen. However, the property of rapid hydrolysis of urea challenges the effective incorporation of N into microbial cells and excess rumen ammonia accumulation will be of no nutritional significance. Hence, a controlled (i.e., slow and sustained)-release of N would be an attractive option to improving the efficiency of N capture in the rumen and microbial protein flow post-rumen, thereby improving the nutritional status and thus, possibly impacting the performance outcome. In this backdrop, this chapter comprehensively discusses the scope and limitations of slow-release N from theoretical perspectives to practical ruminant feeding based on the information emanated from research publications and patents.