Under the restrictions of feeding conditions, the market of breeding industry is not controllable, feed nutrition will become the most easily controlled factors. There is a strong correlation between the level of feed nutrition and the immunity and disease resistance of laying hens. The following is the relationship between vitamin and immunity of laying hens.

　　Although the proportion of vitamin in the mixed feed of laying hens is very small, it plays a very important and irreplaceable role in ensuring the health of the body, especially the immunity of the body.

　　1、vitamin A

　　Vitamin A plays an important role in maintaining the normal growth, development, reproduction and immune function of laying hens, which can improve the immunity of laying hens. In the experiment, it was found that sufficient vitamin A plays an enhanced role in the immune effect of Newcastle disease vaccine. The appropriate amount of vitamin A added in the full price compound is 9,000 IU/kg~ 12,000 IU/kg. Excess levels of vitamin A in chickens (some increased several times) can compensate for reduced hatching rates, motor disorders, blindness, decreased egg production and other immunodeficiencies caused by early vitamin A deficiency.

　　2、VD(Vitamin D)

　　The laying performance and shell quality of laying hens are affected by many factors, but calcium and vitamin D are the most important. The appropriate amount of vitamin D in the full-price compound feed is 2,000 IU/kg~ 4,000 IU/kg. When vitamin D deficiency is severe in the feed, the laying hens begin to develop symptoms within a week (e.g., rickets, eggs with thin shells, lower hatching rate of breeding hens). Chickens that have entered the peak of egg production are sensitive to vitamin D deficiency, resulting in large egg reduction and serious loss.

　　The suitable calcium requirement of laying hens is 3%~4%, but production practice shows that even if calcium supply is sufficient, the problem of broken eggs is still very serious. If additional vitamin D of 1-2 times can solve the problem of calcium absorption very well and effectively improve the quality of eggshell.

　　3、Vitamin E (tocopherol)

　　Vitamin E has immune regulation effect on laying hens, can improve the level of immunity, enhance the resistance to Escherichia coli, viral diseases. Selenium (Se) and vitamin E are ideal immunomodulators for inactivated Newcastle disease vaccine, which can maintain high antibody level in immunized chickens for a long time. Lack of vitamin E in the diet of laying hens may result in low egg production rate, low fertilization rate and hemolytic anemia. Subcutaneous and intestinal bleeding, white comb and other symptoms. The appropriate addition amount of vitamin E in the full-price compound feed is 15IU/kg~30IU/kg, which can improve the use amount of vitamin E when the fertilization rate of breeding chickens is not high and the egg production rate drops for unknown reasons, and can be improved to some extent.

　　4、vitamin C

　　Vitamin C has anti-stress and anti-infection effects. For chickens subjected to heat stress, adding vitamin C can improve egg production, shell strength and egg quality to some extent. Even at room temperature, adding vitamin C to feed can also improve the egg yield, shell quality, fertilization rate and hatching rate of breeder chickens. Vitamin C, like vitamin A, also has an enhanced effect on Newcastle disease antibody levels.

　　Under high temperature, cold, transportation and other stress conditions, and when feed energy, protein, vitamin E, selenium and iron are insufficient, the need for vitamin C in animals increases greatly. However, there is generally no regulation on the need for vitamin C in animals, and it is recommended to add between 100mg/kg and 300mg/kg.

　　5、vitamin B12

　　Vitamin B12 is essential for the normal growth, reproduction and health of chickens. In the case of deficiency, the growth retardation of chickens is anaemic, feed utilization rate is reduced, appetite is inappeased, and even death occurs. The egg production of adult chickens decreases, and the egg shape is small, the hatching rate decreases, and the newborn chicks have abnormal bones. All kinds of animal liver vitamin B12 content is the highest, fish meal, meat and bone meal and other animal protein feed content is also a lot, at present many feed formulations without fish meal and other animal feed raw materials, so, should pay attention to the addition of vitamin B12, recommended amount of 3-20 g/kg.

　　6、choline

　　Choline chloride used as feed additive is usually choline chloride, which plays an important role in ensuring the normal life activities of somatic cells, promoting the normal development of cartilage and the normal operation of the nervous system, etc. The typical symptoms of choline deficiency in chickens are thick and short bone and fatty liver. Generally, choline should be added to the feed of chickens and laying hens, and should be added at any time when preparing the full-price feed at other stages. It is recommended that the amount of choline should be between 300mg and 600mg per kilogram of feed.

　　7、Necessary additions for special periods

　　Various kinds of vitamin preparations on the market are various and can be added appropriately during the period of stress, immunity and disease. It is worth noting that, in the chicken stage, B vitamins can be supplemented, prenatal vitamin A, D needs to increase, after egg production, pay attention to the addition of vitamin D. Vitamin A supplementation should be paid attention to when cotton meal is used to make feed in the diet. High temperature season in drinking water can add vitamin C. However, excessive use of vitamins will not only cause economic waste, but also bring negative effects.

　　Rational use of vitamin feed resources, especially under the conditions of intensive production, livestock and poultry are prone to nutritional deficiency and nutritional metabolism disorders, affecting the growth and development of livestock and poultry, thus causing economic losses. However, there are also many problems for us to choose vitamins. How to choose multi-dimensional products becomes the key. We should avoid taking low unit price as the prerequisite, and products with low nutrition level are products with high unit cost.