Effect of feeding and performance on nitrogen excretion of pigs

Abstract

In highly intensive pig production areas, manure disposal is a major problem especially for nitrogen, in relation to water pollution by nitrates and gaseous ammonia emissions. Nitrogen excretion, in urine and faeces, corresponds to the fraction of dietary nitrogen that is not retained by the animal. When we consider the growing-finishing pigs, 15 to 20% of nitrogen intake is excreted in the faeces and 40 to 50% in the urine, corresponding to a total excretion of 60 to 70% of intake. In practical conditions, we can predict, by modelling, nitrogen excretion by pigs, from protein intake and performance. The results from litterature show that it is possible to reduce nitrogen output preventively, through modifications in the feeding strategy or improvement of performance level. A better adaptation of the diets to each physiological or growing stage, and the improvement of protein quality are two complementary approaches for reducing N excretion. With these cumulative beneficial effects, it may be expected that N output in the slurry and in the atmosphere can be reduced by 15 to 25%, through better feeding management, without any important increase in feed costs. The positive effect of the improvement of performance level has also to be noticed. In breeding sows the most important parameter is the number of piglets produced per sow and per year, whereas for fattening pigs, feed conversion ratio is of primary importance.