TRYPTOPHAN SUPPLEMENTATION OF DIETS FOR GROWING-FINISHING PIGS

A feeding experiment with 112 growing and finishing pigs (barrows and gilts) was carried out to investigate the effects of dietary tryptophan supplementation upon animal performance and carcass characteristics. The basal grower diet was fortified with 0; 0.2; 0.4 of 0.6 g l-tryptophan per kg., whereas to the basal finisher diet 0; 0.17; 0.35 or 0.52 g l-tryptophan per kg was added. In the grower as well as in the finisher diets the rations between total tryptophan and lysine were 18; 20; 22 or 24%. In the growing period (25-50 kg body weight) the dietary treatment with the 24% ratio between tryptophan and lysine yielded significantly higher weight gain when compared to the negative control group, while tryptophan supplementation exerted no significant effect upon feed intake or feed conversion. From the exponential regression between daily weight gain and percent dietary tryptophan, a 0.23% dietary requirement of this amino acid in the growing phase could be derived corresponding with 23% of the dietary lysine content. In the finishing period (50-100 kg body weight) there were no significant differences in growth rate between experimental groups, but daily feed intake and feed conversion tended to be lower in the negative control group. Based upon the feed conversion data a tryptophan requirement of at least 0.15% in the diet could be estimated for finishing pigs, corresponding with 18% of the dietary lysine. Carcass characteristics (dressing percentage, backfat thickness, carcass length and meat content) were not affected by tryptophan supplementation.