Two experiments were conducted to determine the effect of dietary energy, protein, and fat during the latter parts of the growing period and the early parts of the laying cycle on early egg weight and egg components. In Experiment 1, pullets were fed diets containing two levels of energy (2,816 and 3,036 kcal ME/kg), two levels of protein (14 and 18%), and two levels of fat (0 and 4%) in factorial arrangement from 14 to 18 wk of age. From 18 to 34 wk of age, pullets from all of the growing regimens were fed a 16.5% protein diet. In Experiment 2 (18 to 34 wk of age), six diets were used. The energy, supplemental fat, and protein content of the diets were: T1:2,816 kcal/kg, 0%, 17%; T2:2,816 kcal/kg, 0%, 21%; T3:2,816 kcal/kg, 4%, 17%; T4:2,816 kcal/kg, 4%, 21%; T5:3,036 kcal/kg, 4%, 17%; and T6:3,036 kcal/kg, 4%, and 21%. The data were analyzed factorially with energy constant and fat and protein variable (T1 to T4) and with fat constant and energy and protein variable (T3 to T6). In Experiment 1, 18-wk body weight increased slightly (P < .05) due to increasing the energy or adding fat to the diets, whereas egg weight during the early stages of egg production was increased modestly (P < .05) only due to increasing the energy level. In Experiment 2, when energy was constant, egg weight was increased due to increasing the protein level or adding fat to the diets (P < .05). When fat was constant, egg weight was increased only due to increasing the protein level (P < .05). The increased egg weight under these conditions was due mainly to increasing the albumen weight. The results indicated that egg weight during the early stages of the egg production cycle can be increased due to increasing the protein level from 17 to 21% or by adding 4% fat to the conventional layer diets, and that the beneficial effect of fat on egg weight is independent from its energy effect.

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Whether the association with gut microflora modifies the energy metabolism of chickens was investigated by varying the metabolizable energy consumption level from zero to above the maintenance requirement in the germ-free and conventional states. Single comb White Leghorn chicks were either fasted for 3 d (Expt l), or fed for 6 d at a fixed daily meal intake of 2, 5 or 8 g/d (Expt 2), or 5, 10 or 15 g/d (Expt 3). Changes in carcass energy deposition and heat production indicated that when no dietary energy was available the presence of the gut microflora could benefit the birds by reducing energy losses, whereas when dietary energy was supplied the efficiency of energy utilization was reduced by the presence of the gut microflora. It was concluded, therefore, that the heavy burden of the gut microflora modifies energy metabolism by exerting a buffering or a counter-productive action on the energy utilization of the chicken.

Capsaicin (CAP), a pungent principle of hot pepper, enhanced the energy metabolism of rats through the beta-adrenergic action of CAP itself. The present study was done to clarify the effects of dietary red pepper on feeding behavior, abdominal fat content and laying performance in laying hens. Single Comb White Leghorn laying hens were given diets containing varying levels of red pepper (0, 2 and 10g/kg diet) ad libitum for 10 weeks. The red pepper contains 0.22% CAP. There were no significant differences in feeding behavior in any treatments. This suggests that the receptor for the pungent stimuli might be deficient in chickens. The abdominal fat content and liver color were not altered by dietary red pepper, being implied that the beta-adrenergic action of CAP might be smaller in chickens than in mammals. Laying performances were hardly influenced by dietary red pepper. Roche color fan score and the redness of egg yolk color significantly increased as the dietary red pepper content increased, but the reverse was true for the yellowness and lightness of egg yolk color. In conclusion, it is difficult to depress the excess fat deposition of laying hens by dietary red pepper through the action of CAP. Dietary red pepper is only available for the egg yolk pigmentation, particularly in redness.

The e#ect of L-carnitine supplemented into a commercial diet on egg weight, albumen height, Haugh unit, yolk weight and albumen weight of eggs from laying hens was examined. The levels of dietary L-carnitine supplementation were *, ,/, /* and ,** mg/kg. Laying hens were given the diets for 2 weeks. Albumen height and Haugh unit were the highest in the ,/ mg/kg L-carnitine group. When L-carnitine was added at the levels of more than /* mg/kg, yolk weight was significantly increased. In conclusion, dietary L-carnitine supplementation had a beneficial e#ect on albumen quality and could modify the components of the edible part of the egg.