Effect of amino acid levels during broiler breeder pullet rearing on: 2. Egg weight and characteristics from 26 to 34 wk of age

Amino acid pullet nutrition affects growth and development and it is important to evaluate potential effects on egg traits. One experiment was conducted to determine the effects of four amino acid (AA) dietary levels fed to broiler breeder pullets during the rearing phase from 5 to 24wk of age on egg characteristics. A total of 1,360 Cobb-500 slow-feathering pullets were placed in 16 floor pens (85/pen). Up to 4wk all pullets were fed one starter diet in crumbles and after 29d of age fed with four mash grower diets containing 4 AA levels (0.40, 0.54, 0.60, and 0.66% of dLys with balanced protein) and 2,700 kcal/kg ME. From 16wk to 5% egg production, developer mash diets with 2,800 kcal/kg ME and 0.51, 0.57, 0.63, and 0.69% of dLys were offered. Feed amounts varied slightly (±3 g/d) among treatments in the developer phase to maintain BW close (±2%) to Cobb guideline. After 5% egg production all hens were fed one common layer diet and feed increments were made according to egg production by treatment. Onset of egg production occurred at 165d and reached 5% at 167d of age. Egg weights (30/pen) were evaluated after all treatments reached 50% egg production at 26, 28, 30, 32, and 34wk of age. Eggshell color, strength, and thickness were evaluated in 6 eggs/pen at 30wk. Egg components, albumen, yolk and eggshell percentages were calculated and Haugh units measured. Data was analyzed in a CRD with 4 AA treatments and 4 replicate pens each. One-way ANOVA and regression analyses were conducted. Results indicated that AA levels affected (P < 0.05) egg weight up to 28wk. Hens fed the highest AA level during rearing had eggs up to 2 grams heavier than hens fed the lowest AA level and the other treatments were intermediate. There was a linear effect (P < 0.01) of AA levels on egg weight up to 28wk. However, no effects (P > 0.05) of dietary treatments during rearing on egg weight were detected at 30, 32 and 34wk. No effects (P > 0.05) on eggshell color, thickness, yolk color or egg components were observed. Eggshell strength and elasticity (P < 0.05) of hens fed the highest AA level during rearing was lower (37.9N) than eggs from hens fed the two lowest AA levels (42.5N). In conclusion, AA dietary levels during rearing affected initial egg weight and eggshell strength.

Key Words: amino acids, pullet breeders, egg weight, eggshell strength.