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.
ASSOCIATION OF POLYMORPHISMS IN PROLACTIN RECEPTOR AND MELATONIN RECEPTOR 1C GENES ON EGG PRODUCTION AND EGG QUALITY TRAITS OF JAPANESE QUAILS (COTURNIX COTURNIX JAPONICA)
