Effects of dietary supplementation of vitamin C on productive performance, egg quality, tibia characteristics and antioxidant status of laying hens

The objective of the current experiment was to investigate the effects of dietary supplementation of vitamin C on productive performance, egg quality, tibia characteristics and antioxidant status in laying hens raised under normal temperature conditions. A total of 504 46-week-old Hy-Line Brown laying hens were allotted to 1 of 6 dietary treatments with 7 replicates in a completely randomized design. A commercial-type basal diet was formulated without inclusion of supplemental vitamin C. Five treatment diets were prepared by adding 250, 500, 1000, 2000 or 3000 mg/kg vitamin C to the basal diet. Hens were raised under normal temperature conditions (20.3°C of room temperature and 60% of relative humidity, on average) for 6 weeks. Results indicated that increasing supplementation of vitamin C increased (quadratic, P < 0.05) hen-day egg production and egg mass, and decreased feed conversion ratio (quadratic, P < 0.05) and the incidence of broken and shell-less eggs (linear and quadratic, P < 0.01). The positive effects on productive performance were observable for hens fed diets supplemented with 250 mg/kg vitamin C, but no further improvements at the supplemental levels of over 250 mg/kg vitamin C were identified. Egg quality, tibia characteristics and liver antioxidant status were not affected by increasing supplementation of vitamin C in diets. Gene expression of l-gulonolactone oxidase was increased (linear, P < 0.05) in the kidney by increasing supplementation of vitamin C in diets; however, this increase was not observed in the liver. Increasing supplementation of vitamin C in diets improves productive performance of laying hens but has no effects on egg quality and tibia characteristics. The quadratic improvements in productive performance suggest that dietary supplementation of 250 mg/kg vitamin C is recommended for laying hens raised under normal temperature conditions.