Calcium deficiency is a common metabolic disease in pig production. In most cases, the body temperature is normal, the pulse and respiratory rate are normal or slightly increased, and occasionally there are secondary infections in which the body temperature rises, and the pulse and respiratory times increase significantly. Most of the pigs had swaying in the early hindquarters, and the spirit was depressed in the later stage. In severe cases, they were drowsy. The hindquarters were not sensitive to pain. The urine was pale yellow or yellow. The stool was dry and spherical, and the appetite and drink desire decreased. Those with mild symptoms can barely support for a while, but they can't persist for a long time.
Most people think that as long as the calcium content in the feed increases the occurrence of calcium deficiency. However, in actual production, when the calcium content in the feed is sufficient, calcium deficiency still occurs. What is the reason? We talk about the metabolism of calcium in animals.
Calcium mainly plays the following four aspects in the body: first, calcium is an important substance in bone formation; second, calcium is involved in the contraction process of muscles (including bone hunger smooth muscle); third, calcium is involved in neurotransmitters. Synthesis and release, hormone synthesis and secretion; Fourth, calcium ions are coagulation factors involved in the blood coagulation process.
In normal pigs, calcium accounts for about 1.5%-2.2% of body weight. 99% of the calcium is present in the bone and teeth in the form of hydroxyapatite, and the rest is distributed in body fluids and soft tissues, and exists in a dissolved state.
Calcium in plasma is called blood calcium. The blood calcium content is relatively stable, and its concentration depends on the relative balance between calcium and phosphorus absorption and excretion, calcification and decalcification. When the blood calcium concentration is insufficient, the body will automatically adjust to take more calcium from the digestive tract, reduce calcium excretion, and mobilize calcium in the bone to supplement blood calcium.
Calcium in the body is mainly supplied by food. Most of the calcium in food is complex calcium, which must be converted to free calcium ions to be absorbed by the intestines. When the pH in the intestine is less than 6, it is beneficial for the release of calcium ions. Since the small intestine microvilli have very low calcium ion permeability, a special transport carrier is required. It is known that there are a variety of calcium-binding proteins in intestinal mucosal cells, which have a strong affinity with calcium ions and can promote calcium absorption. The ratio of calcium to phosphorus in the feed is generally 2-2.2:1. Excessive phosphorus content leads to a decrease in the absorption capacity of the intestinal tract for calcium. If the feed contains interfering substances such as oxalic acid, it will reduce the utilization rate of calcium.
Therefore, when the calcium content in the feed is insufficient, the pH of the digestive tract is high, and the ratio of calcium to phosphorus in the feed is imbalanced or contains more oxalic acid, the pig's intake of calcium is insufficient.
Calcium metabolism is mainly regulated by hormones such as 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), parathyroid hormone and calcitonin.
Parathyroid hormone (PTH) is synthesized and secreted by the parathyroid main cells. PTH can promote the transport of intracellular calcium ions to the extracellular fluid. The effect on the kidney is mainly to increase the reabsorption of calcium ions by renal proximal tubules and to inhibit the reabsorption of phosphorus by renal tubules. The effect of PTH on calcium absorption is indirectly activated by activating kidney 1α-hydroxylase and promoting the synthesis of 1,25-(OH)2D3, which occurs more slowly. PTH has a dual role in promoting osteogenesis and osteolysis. Experimental studies have shown that low-dose PTH can promote osteogenesis, while large doses can promote osteolysis. The overall effect of PTH action is to increase blood calcium.
Calcitonin is a single-chain polypeptide hormone secreted by thyroid follicular cells (also known as C cells). The target organs of CT are mainly bone and kidney. The effect is opposite to that of PTH. Its function is to inhibit bone breakage, inhibit the reabsorption of calcium and phosphorus, and reduce blood calcium and blood phosphorus.
1,25-(OH)2D3 is a hormone that is metabolized by vitamin D3 in the body. Vitamin D3 in food can be absorbed in the intestines. The cholesterol metabolism intermediate in the skin is first converted to previtamin D3 under ultraviolet irradiation, and the latter is automatically isomerized to vitamin D3 under body temperature for 36 hours. 1,25-(OH)2D3 can promote the small intestine to calcium and phosphorus. Absorption; can promote renal tubular reabsorption of calcium and phosphorus. However, this effect is weak and in a secondary position. The overall regulation effect of 1,25-(OH)2D3 is to increase blood calcium and blood phosphorus.
Therefore, when the pig's parathyroid function is dysfunctional, or the body lacks vitamin D, it can also lead to calcium deficiency.
To solve the problem of calcium deficiency in pigs, we must first understand what causes calcium deficiency.
If the calcium content in the feed is low , try to increase the calcium content in the feed. This situation occurs when there are more wheat bran or when the sow is postpartum.
If the calcium content in the feed is calculated to be sufficient , consider whether the ratio of calcium to phosphorus in the feed is imbalanced or the feed contains anti-calcium absorption components such as oxalic acid.
If the pig does not see the sun for a long time , there may be a problem of vitamin D deficiency. It should be noted that vitamin D is added to the feed.
In the presence of kidney disease in pigs, calcium deficiency may occur due to too much calcium loss; when there is disease in the digestive tract, calcium deficiency may occur due to high pH of the digestive tract or problems of the intestine itself; when the pig persists in acidosis for a long time, It can lead to calcium loss in the bones. These conditions require separate treatments.
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