Effects of dietary tryptophan deficiency in finishing pigs, according to age or weight at slaughter or live weight gain

Abstract

Abstract 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 the effects of dietary tryptophan (TRP) deficiency (0.10 vs. 0.13%) on feed intake, growth performance, body composition and tissue gain, and meat quality, according to age or BW at slaughter or BW gain. TRP deficiency depressed feed intake, growth performance, and tissue (muscle and fat) gains, with less pronounced effect with advancing age. Females were more sensitive to TRP deficiency than castrated males. The weights of lean and fat joints both decreased with TRP deficiency in pigs slaughtered at the same age, with no resulting change in carcass composition, while they were similar to those in control animals after slaughter at the same BW. The addition of dietary limiting TRP affected carcass conformation through preferential stimulation of development in depth (forehand, hindquarter) compared to development in length, thus producing longer carcasses at the same age at slaughter, but shorter carcasses when pigs were slaughtered at the same BW. This was also the case after feed restriction, for similar gain as in TRP-deficient animals. There was no effect of dietary TRP on muscle quality characteristics. The results were discussed in relation to the common stimulating effect of the limiting dietary factor for growth, whether amino acid or energy, on the development of the early maturing body compartments and the resulting changes in carcass conformation according to age or weight at slaughter.