Nitrogen budgets and losses in livestock systems

Abstract

Livestock farming systems encompass (i) grazing, (ii) mixed, and (iii) land-less systems. These systems convert crop protein into animal protein with an efficiency ranging from 5% to 45%, depending on animal type, system and management. The nitrogen (N) in the remaining fraction (55-95%) is in urine and dung, and is conducive to N losses. This paper reviews N input-output budgets and N losses in livestock farming systems. Systems differ in N inputs, outputs and budgets. Generally, N inputs and N losses increase in the order grazing systems < mixed systems