The relationship between body weight gain, nutrient intake, and skeletal and muscle growth in broiler breeder pullets was studied in two experiments. A total of 720 and 540 pullets were started in Experiments 1 and 2, respectively. In the first study, growing pullets were fed either a 15% protein, 2,885 kcal ME/kg pullet grower diet or a 23% protein, 3,133 kcal ME/kg broiler starter diet from 2 to 16 wk of age. Within each dietary treatment, there were three body weight groupings (light, control, heavy) achieved by manipulating weekly feed allowances. At 8, 12, and 16 wk of age, 12 pullets from each diet and body weight grouping were killed for muscle [pectoralis major] and skeletal (shank, keel, tibia, clavicle) measurements. As body weight increased, so did skeletal growth, but there were no significant differences in skeletal measurements related to diet. At 12 and 16 wk of age, pullets fed the broiler starter diet had significantly larger p. major muscles. In Experiment 2, growing pullets were fed restricted diets: 1) the 15% protein grower diet (control), 2) the broiler starter diet adjusted weekly to the same calculated calorie intake as that obtained with the grower diet (broiler starter calorie), or 3) the broiler starter diet adjusted to the same calculated protein intake as the grower ration (broiler starter protein). At 16 wk, there were no significant differences between body weight or skeletal measurements of the control and broiler starter calorie treatments. Pullets in the broiler starter calorie treatment did have significantly larger pectoralis muscles and less abdominal fat than those fed the 15% grower diet. Pullets in the broiler starter protein treatment were significantly lighter and had shorter bones, less abdominal fat, and smaller p. major muscles than those in the control treatment.

In Experiment 1, two groups (n = 180) of breeder pullets were selected at 16 wk from two larger groups with BW of either 1,591 +/- 43 (LBW) or 1,988 +/- 59 g (HBW). From 16 wk of age until a peak feed allotment of 159 g per bird per day, weekly feed allowances were increased in a low (LOW), medium (MED), or high (HIGH) manner. There were significant differences (P less than .05) in BW between the LBW and HBW treatments through 32 wk of age. Within each pullet weight class, the HIGH treatment was numerically heaviest through 32 wk. The HBW hens had significantly improved hen-day production from 24 to 28 (P less than .001) and 28 to 32 wk (P less than .06). The LOW treatment resulted in significantly poorer production in both the LBW and HBW weight groups from 24 to 28 wk. There were no signficant treatment effects on egg weight at a given age. Within each pullet treatment, the HIGH treatment resulted in an increased percentage of double yolked (DY) eggs from 24 to 28 wk (P less than .05) and 28 to 32 wk (P less than .07). In experiment 2, pullets in each of two pullet treatments received approximately 12 kg of feed from 2 to 24 wk of age. One treatment received a greater quantity of feed early in the rearing period (HEAVY) while pullets in the other treatment received a greater quantity of feed later in the rearing period (LIGHT). One-half of the pullets from each rearing treatment were fed either a 14% (LOWPRO) or 18% (HIGHPRO) protein diet during the prelay period (18 to 24 wk). Pullets in the HEAVY treatment were significantly heavier (P less than .01) than those in the LIGHT treatment at 21 but not at 24 wk. The HIGHPRO treatment resulted in a significant improvement (P less than .05) in hen-day egg production from 24 to 28 and 28 to 32 wk. There were no treatment effects on egg weight, and the LOWPRO treatment resulted in a significant increase (P less than or equal to .01) in the number of DY eggs from 28 to 32 wk.

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