Impact of nutrition on nitrogen, phosphorus, Cu and Zn in pig manure, and on emissions of ammonia and odours

In order to reduce N, P and trace elements in pig manure, research toward a better agreement between supply and requirement has been undertaken in recent years, and ways to improve the biological availability of these elements in feedstuffs have been investigated. Substantial reduction in N excreted by pigs can be achieved by phase feeding combined with a better adjustment of the dietary amino acid balance. Feeding pigs with low N diets also allows a reduction of ammonia emission and to some extent the production of malodorous compounds. Phase feeding is also effective in reducing P excretion. However, low digestibility of P in feeds remains the main problem, although it is partly alleviated by the supplementation of pig diets with microbial phytase and the use of highly digestible mineral phosphates. In the same way, lowering Cu and Zn dietary supply is obviously an efficient way to reduce pigs' excretion of Cu and Zn. In a whole-farm perspective, improving the efficiency of nutrient utilisation by the animals is an efficient way to reduce import of nutrients from outside the farm and decrease the environmental risks.