Vitamin D Is Not a Limiting Nutrient Regarding Growth Performance and Tibia Parameters in the Rearing Period of Laying Hens Bred for High Laying Performance Compared to Non-Selected Resource Populations.

Bone damages in laying hens are of great concern in poultry farming. Besides various risk factors like housing systems or nutrient supply during egg production, it has often been hypothesized that genetically high-performing laying hens may be more prone to bone damages. The relevance of dietary support during the rearing period of pullets for optimal bone development has been little addressed so far. In the present study, an increasing dietary vitamin D content within EU legislation was tested during the first 12 weeks of life in two high and two moderate-performing pullet lines (white and brown layer lines). For this purpose, a total of 940 chickens of both sexes were housed at the Institute of Animal Welfare and Animal Husbandry (Friedrich-Loeffler-Institut, Germany). The three experimental diets differed only regarding the added vitamin D amount (300/1000/3000 IU Cholecalciferol/kg diet). After every 4 weeks, randomly chosen animals per genotype and dietary treatment were slaughtered for dissection. Serum 25(OH)-Vitamin D concentrations reflected the dietary treatment. Body weight differed regarding genotype. No effect of dietary vitamin D content as a single influence factor on bone parameters like breaking strength, bone dimensions or mineral content could be shown, but age, sex and genotype had impacts and influenced traits in an interactive manner. Therefore, during the first 12 weeks of the rearing period of layer pullets, the different dietary vitamin D contents did not influence performance or bone parameters in the four genetically diverse purebred layer lines. Adjusted dietary vitamin D recommendations for pullets depending on genetically predetermined egg-laying performance do not appear to be necessary if dietary vitamin D contents are within EU legislation.