Amino acid requirements of pigs. 3. Requirement for apparent digestible threonine of pigs in different stages of growth.

The requirement for threonine of pigs was examined in feeding experiments on individually housed pigs in the live weight range 45 to 105 kg and on group-housed pigs in the live weight range 65 to 95 kg. Lysine supply corresponded with the lysine requirement of growing-finishing pigs. To a negative control diet, containing 134 g kg* 1 crude protein and 4.5 g kg- 1 threonine, three levels of supplements of L-threonine (0.6, 1.2 and 1.8 g kg -1 ) were tested. These results were compared with those of a positive control diet containing 152 g kgcrude protein and 5.7 g kg -1 threonine. To prevent other amino acids than threonine to be limiting, the negative control diet was supplemented with lysine, methionine, trypto­ phan, isoleucine, histidine and valine. The positive control diet was only supplemented with lysine and methionine. The requirement for total threonine of growing-finishing pigs for maximum growth performance was found to be approximately 5.6 g kg-' in a diet contain­ ing 9.4 MJ NE f kg -1 . This figure corresponds with approximately 4.7 g kg~' apparent fae­ cal digestible threonine and 4.3 g kg-' apparent ileal digestible threonine. There was no sig­ nificant difference in response between the growing and the finishing pigs. The requirement for ileal digestible threonine, relative to ileal digestible lysine requirement, was approximately 64 %. It appeared, that dietary protein levels can be reduced with 2 percentage units without any disadvantageous effect on growth performance, when limiting amino acids are sup­ plemented sufficiently.