Effect of high concentrations of dietary vitamin D3 on pullet and laying hen performance, skeleton health, eggshell quality, and yolk vitamin D3 content when fed to W36 laying hens from day of hatch until 68 wk of age

The objective of this experiment was to investigate the effects of various dietary concentrations of vitamin D-3 (D-3) on pullet and laying hen performance, eggshell quality, bone health, and yolk D-3 content from day of hatch until 68 wk of age. Initially, 440 Hy-line W36-day-old chicks were randomly assigned to 5 dietary treatments: 1,681 (control); 8,348; 18,348; 35,014; 68,348 IU D-3/kg. At 17 wk of age, pullets were assigned to experimental diets with 12 replicate groups of 6 birds. At 17 wk of age, pullets fed diets containing 8,348 and 35,014 IU D-3/kg had an increased bone mineral density in comparison to the control fed birds (P <= 0.01). Body weights of pullets fed the diet with 68,348 IU D-3/kg were lower than other treatments (P <= 0.01). Hen-housed egg production (HHEP) of hens fed the 35,014 IU D-3/kg diet was increased in comparison to control-fed hens (P <= 0.01), whereas HHEP of those fed 68,348 IU D-3/kg diet was reduced in compar-ison to all other treatments (P <= 0.01). Shell breaking strength of eggs from hens fed 8,348, 35,014 and 68,348 IU D-3/kg was increased in comparison to eggs from control-fed birds (P <= 0.01). Fat-free tibia ash content of hens fed any of the diets supplemented with D-3 (8,348 to 68,348 IU D-3/kg) was increased in comparison to control-fed hens (P <= 0.05). Yolk D-3 content increased linearly with dietary D-3 and the D-3 transfer efficiency for the control, 8,348 IU, 18,348 IU, 35,014 IU, and 68,348 IU D-3 treatments were 8.24, 10.29, 11.27, 12.42, and 12.06%, respectively. These data suggest that supplementation of dietary D-3 up to 35,014 IU D-3/kg feed maintained if not increased laying hen performance and enhanced pullet and laying hen skeletal quality as well as yolk D-3 content and eggshell quality. Feeding pullets at a higher level 68,348 IU of D-3 resulted in reduced growth and ultimately decreased performance of laying hens.