In pig production, the reduction of nitrogen (N) input into soil via application of manure and the mitigation of ammonia
(NH3) and greenhouse gases emission into the atmosphere drew the attention of governmental regulations and of customers.
In general,the N excretion of pigs can be divided in an inevitable partthat occurs due to normalturnover processes of protein
in the animals (Tamminga, 2003), and another evitable part that occurs due to overconsumption of crude protein (CP) or
consumption of unbalanced ratios of amino acids (AA) in the diet (Aarnink and Verstegen, 2007; Rademacher, 2000). Hence,
strategies to reduce environmental impact of animal husbandry include reduction of N supply via feed by phase feeding
(Rademacher, 2000)