The Interaction Between Dietary Valine and Tryptophan Content and Their Effect on the Performance of Piglets

Four experimental diets for newly weaned pigs were formulated: (1) low valine and low tryptophan; (2) low valine and high tryptophan; (3) high valine and low tryptophan and (4) high valine and high tryptophan. Dietary standardized ileal digestible (SID) lysine content was 1.06 g/kg. The SID valine to SID lysine ratio was 0.58 and 0.67 for the low and high valine diets, respectively, and SID tryptophan to SID lysine ratios were 0.19 and 0.22 for the low and high tryptophan diets, respectively. In total, 64 pens of 6 pigs (3 barrows and 3 gilts) were divided over the four experimental treatments. No interaction between dietary supply of valine and tryptophan was observed (P > 0.1 for all parameters). Increasing the dietary valine content increased the daily feed intake, daily gain and gain:feed (P < 0.001 for all three parameters). Increasing the dietary tryptophan content improved gain:feed during the first 2 weeks (P < 0.05) and overall (P < 0.05). Valine supply had a greater effect on performance results than tryptophan supply. It may thus be beneficial to provide a diet with an optimal dietary concentration of valine even if other amino acids are at suboptimal dietary levels.