The effect of dietary manipulations of energy, protein, and fat during the growing and laying periods on early egg weight and egg components.

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.