What are the nutrient requirements of pigs?
Mineral elements generally account for only 3%-4% of the pig's body, and are the main component of bones. Some are distributed in the hair coat, muscles, blood and other soft tissues, and some are components of vitamins, hormones and enzymes. Although these elements are not a source of energy, they play a role in participating in metabolism, regulating osmotic pressure and maintaining acid-base balance. They are necessary for maintaining the normal physiological functions and production of pigs, and they are also the framework that supports the body's form. There are many kinds of mineral elements; according to their content in the body, they are divided into two major categories: macroelements and microelements. Macroelements are elements that account for more than 0.01% of body weight, such as calcium, phosphorus, sodium, chlorine, sulfur, magnesium, potassium and other elements; microelements are those that account for less than 0.01% of body weight, such as iron, copper, manganese, zinc, iodine, selenium and other elements.
(1) Macroelements
1. Calcium and phosphorus: These are the elements required in the greatest amounts by the pig's body and are the main components of bones.
Calcium plays an important role in maintaining the physiological functions of nerves, muscles and the heart, as well as in regulating acid-base balance, promoting blood coagulation and forming bones. When calcium is deficient, rickets, osteomalacia, reduced bone growth and slow growth, and poor appetite occur, and pica, coma in suckling piglets, cramps and jumping and other symptoms often occur. Because lactating sows excrete large amounts of calcium, calcium deficiency can lead to paralysis. Boars show incomplete sperm development.
Generally, the calcium content in pig diets accounts for 0.8%-0.9%; for piglets and lactating sows it should account for 0.9%, and for other pigs 0.8%. The relationship between calcium and energy is that when energy increases, calcium should also increase. However, if the amount of calcium is too high, it will affect the pig's absorption of magnesium, manganese and zinc, and is also unfavorable to its growth, development and production. Generally, cereal feeds and bran contain very little calcium, so calcium feeds such as stone powder, bone meal and calcium hydrogen phosphate should be added to pig diets.
As a component element of bones, phosphorus content is second only to calcium. Phosphorus plays an important role in carbohydrate and fat metabolism, the absorption and utilization of calcium, and the maintenance of acid-base balance. The symptoms of phosphorus deficiency are the same as those of calcium deficiency. The pig's requirement for phosphorus is 0.6%-0.7%. Cereals and bran contain more phosphorus, but it mainly exists in the form of phytic acid phosphorus, and the pig's utilization rate of phytate phosphorus is very low. Therefore, when formulating diets, available phosphorus should be used as the indicator of phosphorus requirement.
Calcium and phosphorus have a close relationship; an excessively high content of one element in the feed will affect the absorption and utilization of the other element. Therefore, the two must maintain a certain ratio. The ratio of calcium to phosphorus is generally required to be (1.5-1.2):1.
In addition, vitamin D also affects the absorption and utilization of calcium and phosphorus. If the diet lacks vitamin D, calcium and phosphorus cannot be well utilized either, and this will likewise cause calcium and phosphorus deficiency in pigs.
2. Sodium and chlorine: These are important components of blood and body fluids. They play a regulatory role in maintaining osmotic pressure and water and acid balance in the pig's body. At the same time, they are also closely related to regulating cardiac muscle activity, protein metabolism, blood circulation, body temperature, increasing appetite, and the hydrochloric acid that forms digestive juices. If the feed lacks both, pigs will have reduced appetite, slow growth and pica. It can be seen that whether or not salt is added to the feed is crucial. However, salt must not be excessive, otherwise it will cause poisoning or diarrhea. The most suitable amount is 0.5%-1.0%.
(2) Microelements The microelements required by pigs include iron, copper, zinc, manganese, cobalt and iodine. Their functions for pigs are as follows:
1. Iron and copper: Iron is an important component of hemoglobin, hemosiderin, myoglobin, cytochrome enzymes and so on in the pig's body. Iron deficiency causes anemia, and piglets are especially prone to anemia, so newborn piglets should be injected with iron dextran or blood-producing agents. Copper and iron have a close coordinated effect; copper participates in the digestion and metabolism of iron and speeds up the formation of hemoglobin, so copper deficiency likewise causes anemia. In recent years, research has found that copper also has the effects of promoting growth, enhancing immune function and resisting bacteria. The daily iron requirement, calculated according to body weight at different growth stages, is 22-250 mg; the copper requirement is 1.3-9.33 mg, and copper can be even higher in high-copper feeds.
2. Zinc: It is a component of many metabolic enzymes, and is especially an indispensable element for the composition of carbonic anhydrase in the pig's cortex. This enzyme plays an important role in skin metabolism and hair gloss. The skin of zinc-deficient pigs is prone to keratinization, dryness and cracking, and hair loss, growth is slow, and they are prone to dermatitis and so on. The daily requirement is 22-155 mg. Generally, feed is deficient in zinc, so attention should be paid to adding zinc when formulating compound feed.
Manganese: It exists in the pig's liver, bones, spleen, pancreas and pituitary gland. It plays a role in bone formation, growth and development, and is a component of some enzymes in the metabolism of carbohydrates, fats and proteins. Manganese deficiency causes swelling of joints such as the tibia and toe bones, and in severe cases causes reproductive dysfunction in pigs, or the formation of mummified fetuses and stillbirths. The daily requirement is 1-22 mg.
4. Cobalt: It is a component of vitamin B12. Vitamin B12 is a vitamin that prevents anemia and promotes blood formation, so cobalt deficiency likewise causes anemia. 5. Selenium: It is a component of glutathione peroxidase. Selenium deficiency causes myocardial degeneration, liver necrosis, ventricular fluid accumulation, reduced reproductive function and white muscle disease. Piglets are more sensitive to selenium, and quickly die when deficient in selenium. Generally, feed in Henan Province is deficient in selenium, so selenium must be added when formulating pig diets. The pig's daily requirement is 0.03-0.08 mg.
Iodine: It is the main component of thyroxine. Iodine deficiency causes enlargement of the thyroid gland, metabolic disorders and reduced fertility in pigs. The daily requirement is 0.03-0.4 mg.