Three experiments were conducted with broiler chicks where diet composition varied with respect to dietary protein, energy, and essential amino acid (EAA) balance. Birds fed diets varying widely in EAA balance and protein and energy levels performed differently with respect to percentage carcass fat and protein. The absolute carcass protein deposition remained relatively constant between treatments, but body fat content varied depending on level of energy intake. Although abdominal fat content varied with level of dietary protein and energy, these values did not correlate well with total carcass fat deposition. Carcass fat deposition correlated well with dietary energy intake, which in turn appeared to be influenced by birds eating to satisfy their EAA requirement. With diets of similar EAA balance, birds appeared to have similar EAA intakes rather than similar energy intakes. Birds fed diets with similar EAA levels, but varying widely in level of nonessential amino acids, energy, or both consumed similar amounts of feed and deposited similar amounts of carcass protein. The present data suggest that level and balance of EAA can have a significant effect on feed intake, thereby influencing weight gain and carcass composition.

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Chez la plupart des poules nourries avec les raiions exp6rimentales, la production d'oeufs a diminu6 imm6diatement, ir environ 70%. Aprds le pic de ponte, le poids corporel des poules recevant les rations exp6rimentales est demeure constant ou a diminu6, alors qu'il a augment6 normalement chez les poules t6moins. En outre, I'accroissement de la taille des oeufs a 6t6 comparable, que les poules regoivent les rations exp6rimentales ou t6moin. Lors d'une deuxibme exp6rience effectu6e sur des poules plus Agees, la compl6mentation du r6gime experimental d l0% de protdines par de la m6thionine, de la lysine, di I'arginine et du tryptophune aentrain6 une prise de ces acides amin6s dans une proportion 6quivalente uu* "*ig"n""t minimilei du CNRC. La masse d'oeufs a toutefois 6t6 d'environ l1% inf6rieure )r celle obtenuJavec la ration t6moind l7 % de prot6ines. Enhn, bien que I'ingestion de plusieurs acides amin6s essentiels ait 6t6 infdrieure aux exigences, les carences calcul6es dans les deux exp6riences 6taient en accord avec la rdduction de la masse d'oeufs observ6e chez les poules nourries avec les rations exp6rimentales, comparativement aux t6moins.Can. J. Anim. Sci.

A number of experiments were undertaken using White Leghorn pullets to determine the effect of diet and growing treatment on 16-wk body weight and carcass composition. Irrespective of the level of dietary energy, body weight gain and carcass composition appeared to be closely correlated with energy intake of the pullets. Diets as low as 15% protein with and without methionine supplementation resulted in 16-wk body weights similar to those of animals fed diets containing 21% protein, suggesting that protein is not a critical nutrient influencing weight gain of pullets. Pullets fed ad libitum every other day from 12 to 16 wk of age were significantly lighter at 16 wk than pullets full fed a regular grower diet or the regular diet diluted with 20% oat hulls. Pullets must achieve a certain body weight and carcass composition in order to trigger the onset of production. Dietary energy, not protein, appears to be the critical nutrient involved.