Vitamin D and calcium and phosphorus deficiency

99% of the calcium ingested by chickens is used to form bones and eggshells, and the rest of the calcium is distributed in body fluids in a free state, which plays an important role in maintaining the normal function of nerves, muscles and heart and maintaining acid-base balance in the body. About 80% of the phosphorus ingested by chickens is composed of bone together with calcium (bone contains 36.5% calcium and 17% phosphorus), and the rest is distributed in the whole body tissue, which has a wide range of physiological functions.

The rate of action of calcium and phosphorus depends on the content of vitamin D in the feed. In the absence of vitamin D, the absorption and transport of calcium and phosphorus in the small intestine is reduced, the deposition of calcium and phosphorus in the bones of the growing chicks is reduced, and the content of calcium in the egg shell of the laying hen is reduced. The improper proportion of calcium and phosphorus in the diet also affects the absorption and function of calcium and phosphorus. Excessive calcium may lead to calcium, phosphorus imbalance, bone distortion. Excess phosphorus can cause malnutrition in bone tissue. Therefore, calcium, phosphorus deficiency and proportion imbalance, can cause chick rickets and laying hens rickets.

(I) etiology

1. The content of calcium and phosphorus in the diet is insufficient or lacking

First, the formula did not meet the chicken's requirements for calcium and phosphorus when designing the formula. Second, due to the poor quality or adulteration of feed raw materials, the calculated value of the formula does not match the actual content of raw materials, especially the lack of phosphorus is more common.

2. Calcium, phosphorus ratio imbalance

Calcium, phosphorus in the feed to have the appropriate proportion is conducive to the absorption of chicken. The common cause of excessive calcium is feeding chicks or young chickens with the feed of laying hens, or adding too much shell powder and lime to the feed.

3. Insufficient vitamin D in the diet

Vitamin D can regulate the metabolism of calcium and phosphorus and promote the absorption of calcium and phosphorus. If the lack of vitamin D in the feed, even if the calcium, phosphorus content is sufficient can not be fully absorbed.

4. Excess fluorine

As a source of calcium and phosphorus, excessive fluoride content of calcium hydrogen phosphate can affect bone calcification and decalcification of bones.

(II) symptoms

1. Calcium deficiency

Disease chicks are mainly manifested as growth and development is blocked, legs become soft, standing instability, lameness, severe lying on the ground. The chicks also saw that when they were forced to stand, their legs were stiff and forked in the shape of "eight" or bent outward in the shape of "O". They were depressed, lost their appetite, and died of later failure. Calcium deficiency in adult chickens is mainly found in laying hens and is characterized by weakness of legs, paralysis in severe cases, decreased egg production, thinning of eggshells or soft-shelled eggs.

2. Phosphorus deficiency

The clinical characteristics of chicks are sudden onset, obvious lameness and difficulty in standing at the beginning of the disease, rapid progression and high mortality. Symptoms are similar to calcium deficiency.

(III) necropsy change

1. Calcium deficiency

The chick's beak shell becomes soft, and the sternum is bent and deformed. In severe cases, it is "S" shaped. Wing, leg long bone soft and easy to bend, mid-term femur, tibia and metatarsal proximal section visible growth disc widening. The bone of the spine becomes soft and curved in an "S" shape. The lesions with diagnostic significance are the thickening and rounding of the ribs, soft and curved in a "V" shape or wavy shape, and constant folding. The lesions of calcium deficiency in adult chickens are bone thinning and even fractures, especially the vertebrae, ribs, tibia and femur. Ducklings were characterized by soft and pliable ribs and large, white hemispherical projections of mung bean rickets beaded on the inner surface of the backbone.

2. Phosphorus deficiency

The characteristic lesion of the chick is that the ribs are flat and soft but not curved, and the head of the rib (proximal) is fusiform and beaded, gray-white. The characteristic lesion of ducklings is that the ribs are naturally everted and soft, and the middle part is bent into the chest cavity, which is still difficult to restore to its original state by force. The maxilla is extremely soft like rubber and is folded in half continuously. The tibia is mostly curved in arch, the backbone is thickened, and the middle part is mostly fractured and bulbous and hard.

3. Prevention and control

Ensure the appropriate content of calcium, phosphorus and vitamin D in the diet, and the proportion of calcium and phosphorus is appropriate. The suitable amount of calcium in the diet of growing chickens is 0.9%~ 1%, the suitable amount of laying hens is 2.25%~ 3.25%, and the suitable amount of phosphorus is 0.55%~ 0.65%. In use, the calcium and phosphorus contents of the raw materials (such as bone meal, fish meal, shell powder, stone powder, etc.) need to be tested. According to the demand of chickens, the actual addition amount is calculated, and the ratio of calcium and phosphorus should be adjusted. Generally speaking, the ratio of calcium and phosphorus in the growing poultry diet is 2: 1, while that of laying hens is higher, about 3.5: 0.4. The quality of the raw materials used should be guaranteed, and unqualified ones should not be used.

After the onset of the disease, the first test feed to determine the content of calcium, phosphorus and fluorine. If there is more calcium and less phosphorus in the diet, it is necessary to supplement phosphorus while supplementing calcium, such as calcium hydrogen phosphate and calcium superphosphate. If more phosphorus and less calcium in the diet, the main calcium supplement is shell powder. In the absence of laboratory conditions, 1% ~ 2% of high-quality bone meal can be added, and cod liver oil (concentrated cod liver oil or Zhongren Jinwei) can be added at the same time.