Interactive effects of vitamins A and K₃ on laying performance, egg quality, tibia attributes and antioxidative...

Extending laying cycle is a tendency in hen breeding, but egg quality declines as laying hens age. The present study was conducted to investigate the interactive effects of vitamins A and K₃ on laying performance, egg and tibia quality, and antioxidative status of aged Roman Pink laying hens. In a 3 × 3 factorial arrangement, 1 080 87-week-old laying hens were allocated to nine groups with eight replicates in each group. Deficient, adequate and excess vitamins A (0, 7 000 and 14 000 IU/kg) and K₃ (0, 2.0 and 4.0 mg/kg) were supplemented into a basal diet with 1 320 IU/kg of vitamin A and 0.5 mg/kg of vitamin K₃. After 2 weeks of adaption to basal diet, hens were fed corresponding diets for 8 weeks. Vitamins A and K₃ did not significantly affect the laying performance. However, they showed interactive effects on yolk ratio at week 93 as well as tibia weight and diameter (P < 0.05), and hens fed deficient vitamins A and K₃ had the highest yolk ratio and tibia weight, but the lowest tibia diameter. Compared with deficient addition, adequate or excess vitamins A and K₃ increased yolk color at weeks 93 and 97 (P < 0.05). Compared with hens fed deficient or excess vitamins, hens fed adequate vitamins A and K₃ had higher eggshell strength at week 93 or 97 (P < 0.05). Increasing vitamin A elevated plasma total superoxide dismutase (T-SOD) activity and decreased hepatic glutathione peroxidase (GSH-Px) activity (P < 0.05). Excess vitamin K₃ increased hepatic T-SOD activity (P < 0.05). Vitamins A and K₃ exhibited interaction on the activities of antioxidative enzymes in eggshell gland (P < 0.05), and adequate or excess vitamins A and K₃ increased the activities of GSH-Px, T-SOD and catalase (CAT). Adequate and excess vitamin A up-regulated the mRNA expression of GSH-Px1, GSH-Px3 and SOD1 in eggshell gland (P < 0.05). Vitamins A and K₃ showed interactive effects on CAT mRNA expression in eggshell gland (P < 0.05) and hens fed adequate vitamins A and K₃ had the highest CAT mRNA levels. In conclusion, dietary addition of vitamins A and K₃ improved the eggshell quality and yolk color as well as antioxidative status in eggshell gland of aged laying hens. Adequate vitamins A and K₃ showed beneficial effects and excess levels did not exhibit superior effects.