Abstract
Endogenous synthesis of vitamin C may satisfy its requirement for laying hens; however, some previous experiments showed beneficial effects of dietary supplementation of vitamin C in laying hens. Thus, the results are still controversial. The objective of the current experiment, therefore, was to investigate the effect of vitamin C supplementation in diets on productive performance, egg quality, relative organ weight, and tibia strength in laying hens. A total of 504 46-wk-old Hy-Line Brown laying hens were allotted to 1 of 6 dietary treatments with 7 replicates in a completely randomized design. Each replicate had 12 hens. Diets were prepared by supplementing the basal diet with vitamin C at the levels of 250, 500, 1,000, 2,000, or 3,000 mg/kg and were fed to hens for 6 wks. Results indicated that increasing supplementation of vitamin C in diets increased hen-day egg production and egg mass (quadratic, P < 0.05), but decreased production of broken or soft-shell eggs (linear and quadratic, P < 0.01) and feed conversion ratio (quadratic, P < 0.05). These positive effects were observable at the supplementation level of 250 mg/kg vitamin C, but there were no further benefits at the greater levels of vitamin C. Increasing supplementation of vitamin C in diets had no effects on egg quality, except for a decrease (quadratic, P < 0.01) in egg yolk color with increasing vitamin C supplementation. The relative weights of the liver, kidney, and spleen were not affected by increasing supplementation of vitamin C in diets. Tibia strength was not influenced by increasing supplementation of vitamin C. In conclusion, dietary supplementation of vitamin C has a beneficial effect on egg production of laying hens. Quadratic responses of increasing vitamin C supplementation in diets reveal that supplementation of 250 mg/kg vitamin C is recommended for diets fed to laying hens at 46–52 wks of age.
Hematological parameters and productive performance of heat-stressed laying hens as influenced by early heat shock program, sodium bicarbonate and/or vitamin C supplementation
