[Effect of feeding on the excretion of nitrogen in fattening pigs].

In this review possibilities to reduce nitrogen excretion in fattening pigs are discussed. If the weight gain is high, the total nitrogen requirement for maintenance during the (shorter) fattening period is lower. Therefore the amount per fully grown animal is reduced. Diseases can increase the nitrogen turnover considerably. The optimal ratio of protein to energy for nitrogen accretion decreases during the fattening period. By reducing the protein content in the food in 3 steps (3 phase feeding, 160, 140 and 130 g crude protein/kg food) nitrogen can be saved. The addition of synthetic amino acids (lysine, methionine, threonine, tryptophane, isoleucine) allows a further reduction of the protein content in the food without loss of growth yield. The availability of amino acids in the food depends on their prececal digestibility. The main source of ammonia emission is urea, which is excreted renally. Since nitrogen over supply is mainly excreted by the kidney, the reduction of nitrogen by 3 phase feeding and addition of amino acids especially decreases ammonia emission.