Amino acid requirements of pigs. 2. Requirement for apparent digestible threonine of young pigs.

Six trials involving a total of 460 young pigs were performed to study the threonine require­ ment during the live weight range of approximately 20 to 40 kg. To a negative control diet, containing 160 g crude protein and 5.6 g kg-' threonine, four additions of L-threonine (0.0, 0.6, 1.2 and 1.8 g kg -') were tested. Results were compared with those of a positive control diet with 185 g kg-1 crude protein and 6.8 g kg-1 threonine. The negative control diet was supplemented with lysine, methionine, tryptophan, isoleucine, histidine and valine in order to be sure that no other amino acids than threonine were limiting. The positive control diet was supplemented with lysine and methionine. The experimental diets were fed ab libitum as pellets. In two separate trials, the apparent faecal and ileal digestibility of the amino acids of the two control diets was determined. The requirement for total threonine was found to be 7.1 g kg1 for maximum weight gain, and 7.4 g kg-' for maximum efficiency of feed utilization, in a diet containing 2290 kcal kg 1 net energy. These figures correspond with 6.2 and 6.5 g kg-' faecal digestible and 5.7 and 6.0 g kg-1 ileal digestible threonine, respective­ ly. Pig performance on the negative control diet supplemented with the first limiting amino acids, was almost similar to that on the positive control diet.