TRYPTOPHAN REQUIREMENT OF PIGS BETWEEN 60-KG AND 105-KG LIVE WEIGHT

In a growth trial, the tryptophan requirement of castrated male pigs w as determined using the daily gain from 60 to 105 kg and the nitrogen balance at approximately 70 kg live weight as parameters. A total of 1 2 animals per group were fed rations based on maize and peas containin g 12.8 % crude protein, 9 g/kg lysine and 1.0, 1.2, 1.4, 1.6 and 1.8 g tryptophan, on a dry-matter basis. A control ration based on maize an d soy bean meal containing 16.5 % crude protein, 9 g/kg lysine and 1.6 g tryptophan was fed to six animals. All rations were offered at a ra te of 90 g dry matter per kg metabolic live weight. Feeding the ration s containing 1.0 g/kg tryptophan led to a deterioration in growth perf ormance, reduced feed intake and to the developement of skeletal abnor malities. Raising the tryptophan content of the ration led to a more h omogeneous performance within groups and the gradual disappearance of leg weaknesses. Tryptophan requirement was determined to be 1.6 and 1. 8 g/kg dry matter, equalling tryptophan:lysine ratios of 0.18 and 0.20 , using nitrogen retention and daily gain as parameters. Considering t he small effects of higher tryptophan levels on growth performance, a preferable range of tryptophan supplies is suggested. A tryptophan:lys ine ratio lower than 0.16 may lead to adverse effects on feed intake a nd skeletal development.