Vitamin C-Strategy for improving laying hens during the late laying period

Li Mengying; Zhang Lei; Liu Guoqing; Zhang Honghe

Currently, commercial laying hens can be kept past the age of 80 weeks. egg production performance experiences a rapid decline towards the end of the laying cycle [1]. In addition, when the hens' bodies are more likely to produce large levels of free radicals during the later stages of the laying cycle, which in turn hastens the aging process [2]. The negative effects on the performance of late-laying hens are usually mitigated by a nutritional strategy. VitaminC, or L-ascorbic acid(AA), is a water-soluble vitamin which is able to scavenge many oxidative molecules and in multiple functions [3-4]. Studies of vitamin C have focused on its effects on early, peak-laying, or heat stress in poultry, but little work has been done on its effects in late-laying hens [5]. Therefore, the present study was conducted to evaluate the effects of vitamin C on the egg production performance and antioxidant properties of laying hens during the late laying period, and to compare the effects of vitamin C phosphate esters and coated vitamin C.

A total of 480 Hy-line variety brown (58-weekold) were randomly assigned to 5 dietary treatments, with 12 replicates of 8 hens. The control group (CON) received a standard corn/soybean meal basal diet (Table 1), formulated according to the requirement of Hy-line laying hens. The treatment groups were fed the basal diet that containing vitamin C (including vitamin C phosphate and coated vitamin C). After 2 weeks of adaptive feeding, the laying period lasted 6 weeks. Both vitamin C phosphate and coated vitamin C are provided by Zhejiang NHU Company Ltd. The content of vitamin C phosphate is 35 percent and the content of coated vitamin C is 97 percent.

Egg production performance

Antioxidant capacity

As a antioxidant, vitamin C protects the body from the threat of free radicals and increases antioxidant capacity in animals [6]. Antioxidant indicators are important parameters to monitor antioxidant status [7-8].Table 3 shows the concentrations of malondialdehyde (MDA) and the activities of antioxidant enzymes in serum of laying hens. In the serum, the MDA concentration decreased with increasing dietary vitamin C supplementation from 0 mg/kg to 100 mg/kg, the hens fed vitamin C (100 mg/kg) diets had significantly decreased the serum MDA levels (P<0.05). The activities of catalase (CAT) increased with increasing dietary vitamin C supplementation, the hens fed vitamin C (100 mg/kg) diets had significantly increased the activities of catalase (P<0.05). However, there were no significant differences in the superoxide dismutase activity (SOD) and antioxidant capacity (AOC) (P>0.05). Similar to the egg production performance of laying hens, there was no significant difference in the serum antioxidant capacity of laying hens between vitamin C phosphate esters and coated vitamin C at the same level of supplementation (P >0.05). Vitamin C increases antioxidant capacity and relieves the oxidation state of laying hens during the late laying period. While at the same level, vitamin C phosphate and coated vitamin C have similar effects.