EFFECTS OF DIETARY TRYPTOPHAN DEFICIENCY IN FINISHING PIGS, ACCORDINGTO AGE OR WEIGHT AT SLAUGHTER OR LIVE WEIGHT-GAIN

Three experiments were conducted with 188 finishing pigs (females and castrated males) of the Large White breed, between mean body weights ( BW) of 53 and 88 kg, and fed according to a feeding scale, to study th e effects of dietary tryptophan (TRP) deficiency (0.10 vs. 0.13%) on f eed intake, growth performance, body composition and tissue gain, and meat quality, according to age or BW at slaughter or BW gain. TRP defi ciency depressed feed intake, growth performance, and tissue (muscle a nd fat) gains, with less pronounced effect with advancing age. Females were more sensitive to TRP deficiency than castrated males. The weigh ts of lean and fat joints both decreased with TRP deficiency in pigs s laughtered at the same age, with no resulting change in carcass compos ition, while they were similar to those in control animals after slaug hter at the same BW. The addition of dietary limiting TRP affected car cass conformation through preferential stimulation of development in d epth (forehand, hindquarter) compared to development in length, thus p roducing longer carcasses at the same age at slaughter, but shorter ca rcasses when pigs were slaughtered at the same BW. This was also the c ase after feed restriction, for similar gain as in TRP-deficient anima ls. There was no effect of dietary TRP on muscle quality characteristi cs. The results were discussed in relation to the common stimulating e ffect of the limiting dietary factor for growth, whether amino acid or energy, on the development of the early maturing body compartments an d the resulting changes in carcass conformation according to age or we ight at slaughter.