The Effect of Calcium and Nonphytate Phosphorus on Chicken Genetic Line, Egg Production, Shell Quality, Bone Homeostasis, and Progeny Bone Quality

The study consisted of two parts to determine effects of dietary calcium (Ca) and nonphytate phosphorus (NPP) level on four pure genetic lines of broiler breeders. The first part was concentrated on body composition, egg production and shell quality changes according to diet and genetic line. The second part was the study of bone homeostasis variables combining hematology, bone histology and body composition changes according to diet and genetic line. In the study, pullets (246 from each of pure genetic line A, B, C and D) were individually caged and light stimulated at 21 weeks of age. The study duration was from 21 to 50 weeks of egg production. Hens from each line were fed one of six diets varying in calcium and nonphytate phosphorus (NPP): 1) 2.25% Ca with 0.25% NPP; 2) 2.50% Ca with 0.25% NPP; 3) 2.75% Ca with 0.25% NPP; 4) 3.0% Ca with 0.25% NPP; 5) 3.25% Ca with 0.25% NPP; and 6) 3.25% Ca with 0.40% NPP. Daily allotted feed intake was increased for every 8 percent increase in egg production going from 5% to peak. Egg production and egg quality variables were recorded throughout the experimental period. Chicks hatched from breeder hens from each treatment (line x diet) were fed a commercial broiler starter diet for 14 days. At 14 days of age plasma was collected from the chicks for bone specific alkaline phosphatase (BSAP), fibroblast growth factor 23 (FGF23), and tartrate resistant acid phosphatase (TRAP) determination. The breeder study was terminated at 50 weeks of age and blood samples were collected from 1000 hrs to 1300 hrs to evaluate bone homeostasis variables the same as the chicks. Tibia bones from hens were collected for histological TRAP staining. Chicks and hens were scanned with dual energy x-ray absorptiometry (DXA) (GE® Lunar Prodigy) for body composition. Statistical analysis was two-way ANOVA with interaction from two main factors (line and diet) and MANOVA for repeated measures procedure. The results showed, genetic line had effect on both egg production and shell quality (