Le besoin en tryptophane des porcs en croissance (20 - 55 kg)

Two trials were performed on the tryptophan (TRP) requirement of growing pigs (20 - 55 kg). In both trials, diets were formulated to contain 9.8 MJ/kg of net energy and 8.2 g/kg of standardized ileal digestible (SID) lysine (LYS). This LYS level was chosen so that the LYS level would limit the growth of the animals in the trial, allowing the ideal TRP requirement to be assessed as a ratio to LYS. In the first trial (28 - 55 kg), pigs received either: 1) a control, high crude protein (CP) diet (171 g/kg) with an SID TRP:LYS ratio of 22%, 2) a low CP diet (142 g/kg) with an SID TRP:LYS ratio of 17% or 3) a low CP diet (142 g/kg) with an SID TRP:LYS ratio of 20%. The results showed that TRP was limiting for performance in the low CP - low TRP diet. The best results were observed with the control diet, although not significantly different from the low CP - high TRP diet. In the second trial (20 - 44 kg), a low CP - low TRP diet (138 g/kg – 16.5% SID TRP:LYS) was supplemented with increasing levels of TRP (dose-response) to yield different SID TRP:LYS ratios (16.5, 18.0, 19.5, 21.0 and 22.5%). With increasing TRP levels, pigs showed a linear increase in feed intake (P = 0.002) and daily gain (P < 0.001) and a linear decrease in feed conversion ratio (P = 0.003). Although it was not possible to determine a break point with broken line models, the results suggest an SID TRP:LYS requirement greater than 19.5%.