Genotype-dependent impact of dietary vitamin D 3 on laying hens.

Vitamin D 3 has an integral part in calcium and phosphorus homoeostasis, which in turn plays a key role in egg production of hens. The present study aimed to investigate whether an additional vitamin D 3 supplementation improves the laying performance and egg quality of hens according to their genetic potential. For this purpose, four layer lines (low performing: R11 and L68; high performing: WLA and BLA) supplemented either with 300 or 3000 IU vitamin D 3 per kg feed were compared concerning serum 25-hydroxyvitamin D 3 (25-OHD 3 ), calcium, phosphorus and alkaline phosphatase (ALP), laying performance and egg quality. The higher supplementation of vitamin D 3 increased 25-OHD 3 serum concentrations in all genotypes, except for R11 and WLA hens in week 49, and also elevated vitamin D 3 and 25-OHD 3 content in the egg yolk ( p  < 0.05). In week 29, 3000 IU vitamin D 3 decreased pooled least squares means (LSMeans) of serum calcium concentrations considering all genotypes and increased the ALP concentrations in BLA hens ( p  < 0.05). Considering the whole experimental period daily egg mass of R11 hens was increased by an additional vitamin D 3 supplementation ( p  < 0.001). Regarding all genotypes and the whole experimental period the pooled LSMeans of breaking strength of eggs from hens fed 3000 IU vitamin D 3 were higher than those of hens fed 300 IU ( p  = 0.044). In conclusion, present results give evidence that the higher vitamin D 3 supplementation might have genotype-dependently beneficial effects on calcium and phosphorus homoeostasis of hens, which might improve feed efficiency in the early laying period and promote the persistence of the laying period irrespectively of genotype. The increase of serum 25-OHD 3 by the higher vitamin D supplementation supported the higher transfer of vitamin D in the egg yolk and improved genotype-dependently the breaking strength of the eggshell.