EFFECT OF A DIETARY AMINO-ACID DEFICIENCY OR IMBALANCE DURING THE INITIAL PERIOD OF GROWTH IN PIGS ON SUBSEQUENT PERFORMANCE AT SLAUGHTER [French]

摘要

Effect of a dietary amino-acid deficiency or imbalance during the initial period of growth in pigs on subsequent performance at slaughter. A series of 5 experiments was conducted with a total number of 476 Large White pigs (females and castrated males) to study the influence of a deficiency in a particular amino acid (lysine, threonine or tryptophan) and an imbalance between amino acids (excess threonine relative to lysine) during the initial period of growth (18-20 to 40-50 kg live weight) on final performance at 100 kg slaughter when the pigs are fed the same finisher diet at the same feeding level. The results show that the pigs tended to eat more feed per kg metabolic body weight (BW0.75) when fed a suboptimal level of lysine or threonine. It followed that growth depression was associated with increased adiposity, which was maintained at slaughter after the animals were fed the same diet at the same feeding level during the finishing period of growth. Conversely, in the case of tryptophan, a reduced supply below the level for optimum growth severely depressed voluntary feed intake, with a resulting decrease of both lean and fat deposition. Due to this self-limitation of feed intake, the carcasses were leaner at 100 kg slaughter weight, following reequilibrated feeding during finishing. With regard to a dietary imbalance between lysine and threonine, an excess of threonine supply in the presence of a limiting supply of lysine exerted a depressive effect on feed intake and growth performance, as in the case of tryptophan deficiency In the same way, this initial self-limitation of feed consumption, followed by normal feeding during finishing, was associated with lowered fat content in the carcass at 100 kg slaughter weight. On the whole, growth performance during finishing was little or not affected by amino-acid deficiency or imbalance during the former growth period (around 20-50 kg), and this seems to invalidate the phenomenon of compensatory growth. From the observations at slaughter, it seemed that carcass length increased when the former slowing of growth was connected with increased adiposity, as was the case with lysine deficiency. On the contrary, carcass length was not modified or tended to decrease after tryptophan deficiency or excess threonine relative to lysine, that is when lean and fat deposits were both depressed. To conclude, the effects of dietary amino-acid deficiency or imbalance during the initial phase of growth (between 18-20 and 40-50 kg live weight) on the subsequent growth performance at 100 kg slaughter weight are closely related to changes in feed intake according to the type of deficiency or imbalance, and depending on whether lean and fat deposits are distinctly or simultaneously affected.