The inclusion of vitamin A and E in the feed is one of the key factors influencing egg yolk coloration. Vitamin A is an essential fat-soluble vitamin for poultry, playing a crucial role in their growth, development, immune function, and reproduction. Vitamin E is an antioxidant that protects the pigments in the egg yolk from oxidative damage, thereby prolonging the color stability of the yolk.Research has shown that the level of vitamin A in the feed has a significant impact on egg yolk coloration. Adequate supplementation of vitamin A can enhance the color and increase the intensity of the yolk.
One study found that adding an appropriate amount of vitamin A to the feed significantly improved the yolk color index. However, excessively high or low levels of vitamin A can decrease the color index of the yolk. It has been noted that when the addition of vitamin A exceeds 10,000 IU/kg, the color value of the yolk begins to decrease. This is because excessively high levels of vitamin A can slow down the metabolism of carotenoids in the yolk, resulting in reduced color intensity. On the other hand, insufficient levels of vitamin A can lower the synthesis rate of carotenoids in the yolk, affecting the formation of yolk color.
Similar to vitamin A, excessive or inadequate levels of vitamin E can also affect yolk coloration, although to a lesser extent. Excessive vitamin E can inhibit the deposition of cholesterol in the yolk, leading to lighter yolk coloration. Insufficient vitamin E can make the pigments in the yolk more susceptible to oxidation, resulting in poorer coloration.Therefore, it is crucial to properly balance the levels of vitamin A and E in the feed to ensure optimal egg yolk coloration.
