Genetic line, dietary calcium and non-phytate phosphorus, and age affect body composition and tibia ash of broiler breeder hens and their progeny determined by dual-energy X-ray absorptiometry

Body composition of the broiler breeder hen during lay is poorly characterized and it is unknown whether purelines differ in mineral, fat and lean tissue accretion, whether dietary calcium (Ca) and non-phytate phosphorus (NPP) alter it, or whether any difference reaches their progeny. Ninety-six hens from four purelines (A–D; 24 per line, four per diet) were scanned by dual-energy X-ray absorptiometry every four weeks from 21 to 51 weeks, and their progeny were scanned at hatch and 14 days. Diets supplied 2.25 to 3.25% Ca with 0.25% NPP, or 3.25% Ca with 0.40% NPP, equal to 3.08 to 4.45 g Ca and 340 or 550 mg NPP/hen/d at peak allocation. Line, diet and age each affected body mineral content, fat, lean tissue and tibia ash (p ≤ 0.0003). Line C hens had the highest mineral content (134 g; 3.8% of body mass), tibia ash (59.8%) and fat (726 g); line A the lowest mineral content (99 g; 2.9%) and tibia ash (56.9%). Mineral content in grams was lowest at 21 weeks and thereafter stable, so its proportional contribution fell from 3.8 to 2.9% as fat and lean tissue accumulated. The ranking carried into the progeny: 14-day chicks from line C dams had the highest body mineral proportion (2.72%) and those from line A dams the lowest (2.45%; p < 0.0001). Raising NPP from 340 to 550 mg/hen/d increased neither mineral content nor tibia ash. The same line ranking appears in eggshell quality and progeny mineral utilization in companion papers.