Effect of supplementation with two levels of 25-hydroxycholecalciferol on egg internal and external quality in commercial laying hens

Hy-Line Brown layer hens were housed in individual cages from 19 to 80 weeks of age to study the effects of dietary supplementation with two levels of 25-hydroxycholecalciferol (25(OH)D3) on egg internal and external quality, and the amount of cuticle present on the eggshells. Ninety birds were divided into group A (control group) fed with normal commercial layer mash feed, and groups B and C (treated groups) fed with normal commercial layer mash feed plus 0.5 g of 25(OH)D3 [premix (68.9 μg 25(OH)D3)] per kg of feed and 1 g of 25(OH)D3 [premix (137.8 μg 25(OH)D3)] per kg of feed, respectively. There was a significant main effect (P<0.05) of hen age and treatment group on albumen height, Haugh unit, and yolk colour score. There was a significant main effect of both hen age and treatment group on most of the eggshell characteristics such as shell reflectivity before and after staining, difference in shell reflectivity, egg weight, shell weight, percentage shell, shell deformation, shell thickness, and cuticle single score value, whereas a significant interaction between these two factors was seen for yolk colour score and percentage shell. There was a significant effect only of hen age on shell breaking strength and translucency score. The results indicated that the highest albumen height, Haugh unit, yolk colour score, difference in shell reflectivity, and cuticle single score value and lowest shell reflectivity before and after staining were found in group A. In addition, the highest shell weight, percentage shell, and shell thickness and lowest shell deformation were for group C (which is the higher supplemental Hy-D group). Group B was lower than group C for shell weight and percentage shell and higher for shell deformation with group A intermediate, whereas group B was lower than the other groups for egg weight. Shell breaking strength and translucency score were affected only by hen age and there was no significant difference between the three treatment groups for these variables.