Do you know The secret of Calcium and Dairy Diseases?

Dairy cows need a lot of calcium to maintain their lives and produce. Calcium is closely related to cow diseases.

Calcium has the following main functions in dairy cows: it constitutes bone and teeth together with phosphorus; regulates nerve excitability; is related to a muscle contraction; participates in hemagglutination process and has hemostatic effect; is a necessary component of cell coagulation, which can reduce blood vessel permeability; and promotes gastric juice secretion.

1. Calcium (Content and Dynamics) in Cattle

Adults contain about 10 kg of calcium, of which more than 99% is distributed in bones and teeth, and the rest is dissolved in body fluids. Half of the calcium in serum participates in these functions in the form of ions, while the other half binds to proteins. Although the serum calcium content is slightly less, it does not necessarily lead to postpartum paralysis. If there is postpartum paralysis, the serum calcium may not be reduced accordingly. This situation is best solved by adjusting the serum protein level.

Calcium requirement: adult cattle excrete about 10 g of calcium per day, which is mainly excreted through feces. Calcium in urine is less than 1 g per day. Calcium is occasionally discharged from the body surface invisibly. In general, about 1.2 g of calcium is contained in every kilogram of milk. Also, 10 g of calcium is needed daily in late pregnancy due to the needs of the fetus.

The body's essential calcium is obtained from the feed, which is absorbed mainly in the small intestine and in the upper part of the duodenum and jejunum. There are two modes of absorption: active absorption through specific carriers and passive absorption through ion diffusion. Active absorption mainly takes place in the duodenum, and its efficiency is higher; passive absorption mainly takes place in the ileum, and its efficiency is lower.

Cattle absorb a limited amount of calcium from their feed. In large amounts of lactation, 1.6 g of calcium is needed for every 1 kg milk. Also, 10 g of calcium is needed daily for the needs of the fetus in the late period of pregnancy-induced vibration. At this time, the cattle will be deficient in calcium. To maintain the stability of serum calcium concentration. It must be compensated by osteolysis. Usually, about a quarter of bone calcium can be used. If the calcium in bone is 10 kg, the available calcium is 2.5 kg. So bones are a reservoir of calcium. Calcium metabolism of dairy cows is in a negative balance at the peak of lactation, so it is necessary to supplement calcium.

2.Factors Affecting Calcium Absorption

Calcium must be dissolved before it can be absorbed by cows. Insoluble calcium salts such as calcium carbonate and calcium phosphate can become soluble calcium under the action of gastric acid (especially hydrochloric acid secreted by the true stomach). Experiments show that calcium lactate is absorbed well because of its water solubility. It has been proved that insoluble calcium salts such as calcium carbonate and calcium phosphate can be well absorbed only after they are dissolved in water in the stomach. There are many factors affecting calcium absorption. The influencing factors are listed in Table 1.

Table 1 Factors Affecting Calcium Absorption

From Table 1, it can be seen that the absorption rate of calcium depends first on the health status of cattle, age and the requirement of calcium for cattle. (Calcium requirement varies in different growth stages) and whether the amount of calcium is sufficient. Also, the following factors are also important.

2.1 Vitamin D.
Although VD is the most important substance to promote calcium absorption, the product can not play its due role when it acts directly on the intestinal tract as a prototype. It takes 15 hours to feed VD to livestock. This is because this product must be through the physiological role of the liver and kidney, into active VD3 before it can function.

VD3 plays a role by promoting the biosynthesis of calcium-binding proteins.

2.2 Parathyroid hormone. 
It can promote the activation of VD in the kidney, thus promoting the absorption of calcium. When the hormone is deficient, VD3 should be used to compensate.

2.3 Calcitonin. 

It can inhibit the absorption of calcium in the intestinal tract, and also inhibit the activation of VD.

2.4 Lactose.
Amino Acids  Lactose promotes the absorption of calcium, which is evident in distant intestinal segments such as the ileum. Lactose not only promotes the absorption of calcium, but also other divalent ions such as Mg++. On the one hand, the combination of lactose and Ca can increase the permeability of intestinal mucosa, prevent the precipitation of dissolved Ca and insoluble CaC03 in intestinal tract, so that the concentration of Ca++ in intestinal tract can be maintained to a certain extent; on the other hand, it also has the function of removing Ca++ transmission factor in distal intestine.

Xylose, sorbitol, and mannitol also have the function of promoting calcium absorption, but glucose and galactose have no such function.

Amino acids promoting calcium absorption include lysine, methionine, alginic acid, tryptophan, and leucine, among which lysine has the strongest effect. Its main action site is ileum, but glycine has no such effect.

These substances can not be fully transformed without being given orally and can not play their due functions.

2.5  Fat. 
A large amount of fat in the feed can reduce the absorption of Ca, but a small amount of fat can promote the absorption of Ca. Also, fat quality can affect calcium absorption.

3.Calcium-related diseases

Calcium-related diseases are very common, such as foot and limb disease, anterior gastric flaccidity, yogurt disease, hypothermia and so on. The most common ones are postpartum paralysis, which belongs to acute calcium deficiency, and chondroitin, which belongs to chronic calcium deficiency.

Symptoms of Calcium Deficiency in Dairy Cows: Initial depression, slightly hypothermia, molars. Loss of appetite, reduced rumination, weakness, reduced milk production. Long-term pleasure, difficulty in standing, alternate feet when standing, weak shaking hind body, slow reaction, cautious movement, unstable gait, muscle tremor. Sometimes cows are excited, manic, singing and gazing. Paralysis can occur within hours of symptoms.

3.1 Postpartum paralysis.  
The disease often occurs before and after childbirth, especially shortly after childbirth. Postpartum paralysis can be caused not only by a calcium deficiency in cattle but also by rapid changes in calcium balance caused by childbirth and lactation.

The main fruit of postpartum paralysis is treated by oral calcium supplementation and intravenous calcium supplementation, but a large amount of intravenous calcium supplementation should be injected slowly.

In cattle with postpartum paralysis, serum calcium is not only reduced, but also phosphorus is often reduced. With the increase of calcium content, the level of phosphorus can mostly return to normal, but some can not be restored. At this time, the combination of phosphorus preparations should be considered. If treated properly, the sick cow can stand in 30-60 minutes.

3.2 Prevention

3.2.1 Maintain good gastrointestinal function before and after delivery to increase calcium absorption or decrease calcium content.

3.2.2 easy-to-absorb calcium feed (e.g. calcium chloride) is fed before and after delivery.

3.2.3 Feed acidic feed within 5 weeks before delivery.

3.2.4 Feed low-calcium diet within 2 weeks before delivery.

3.2.5 Give vitamin D, 1.5 million IU at a time or 500,000 IU intramuscularly. Given the complex etiology of the disease, cattle with recurrent episodes should be eliminated.

3.3 Chondrosis    
The main symptoms of the disease were difficulty in standing, tight movement, rough skin, slight lameness, and easy fracture after falling. Hemochemical analysis: hypocalcemia, hypophosphatemia, a decrease of CaxP, an increase of alkaline phosphatase, a slight decrease of serum calcium tightness or normal, but a decrease of CaxP product was found in almost all cases.

There are many causes of chondrosis, but there are mainly the following:

3.3.1 VD deficiency: This is considered to be the main cause.

3.3.2 Ca deficiency: Calcium deficiency in feed or weak absorption capacity of dairy cows, especially in large amounts of lactation.

3.3.3 P deficiency: Some believe that phosphorus deficiency has a greater impact than calcium deficiency.

3.3.4 Improper Ca:P ratio: The serious imbalance of calcium and phosphorus ratio is the main cause of the disease. Excess P is easy to cause the Ca absorption barrier.

The disease should be treated according to its etiology. Ca and P should be supplemented first, followed by VD. Ca and P should be replenished after ascertaining the extent and proportion of the deficiency. VD usually takes 1-2 million IU orally or 500 000 IU intramuscularly.

4.Categories and dosage of calcium preparations

Calcium preparations can be divided into two categories according to their components: pure and compound; and injection, powder, and granule can be divided into three categories according to their dosage forms. Table 2 lists the raw materials for the preparation of animal calcium agents.

In the use of calcium preparations, attention should be paid to the differences among different varieties (such as ingredients, characteristics, advantages, and disadvantages), and the dosage forms and varieties suitable for the added conditions should be selected as far as possible. Considering the influence of various factors, the absorption rate of calcium as an additive is calculated as 70%. Water-soluble calcium is best given when a gastrointestinal function is impaired.

For Dutch dairy cows, the amount of calcium maintained could be calculated as 10g/head per day, and 1.6g calcium was added for each kg of milk produced.

Finally, it should be pointed out that calcium is very easy to be deficient from childbirth to the peak lactation period of dairy cows. At the same time, vitamin D, phosphorus and even vitamin A (the content of vitamin A in colostrum is 5-10 times higher than that in normal milk) are often accompanied in this period, which should also be paid attention to.