The main function of fat is to provide energy. Like carbohydrates, fat is the main energy source for pigs. The energy produced by fat is 2.25 times higher than that of carbohydrates with the same weight, and each gram of fat can produce 29.33 kilojoules of heat energy. When pigs ingest organic substances such as carbohydrate, protein and fat from the outside, after digestion, absorption and utilization, the excess part can be converted into body fat and stored under the skin and around the internal organs of pigs, which plays a role in reducing body heat loss and protecting internal organs. When the nutrition of pigs is insufficient, the fat stored in the body can be used to provide energy to ensure the normal growth and production of pigs.
Another function of fat is as a solvent for fat-soluble vitamins. Vitamins A, D, E and K can only be dissolved in fat, so the absorption and utilization of fat-soluble vitamins by pigs must be done with the help of fat.
The third function of fat is to improve the survival rate of piglets and ensure the normal reproduction of sows and the weight gain rate of growing pigs. Adding proper amount of fat to pig feed can improve the production performance of sows, piglets and fattening pigs. If 10% soybean oil or lard is added to the feed of pregnant sows 35 days before delivery, part of the fat can be transported to the fetus through the placenta for deposition, so that the activity of fatty acid oxidase in piglets can be expressed in advance, thus enhancing the energy supply capacity of oxidized fat and increasing the blood concentration of newborn piglets, and reducing the decomposition of blood sugar and glycogen within 12 hours after birth. In addition, adding fat to the feed can improve the lactation yield and milk fat content of sows, so that newborn piglets can get enough energy, greatly enhance the anti-stress ability of piglets and improve the survival rate of piglets. Adding proper amount of fat to the feed of lactating sows can not only improve lactation ability, but also reduce fat loss of sows during lactation, which is beneficial to early estrus and mating after weaning. Adding proper amount of fat to the feed of growing-finishing pigs can improve the weight gain rate and feed utilization rate by 5% ~ 10%. The fat supply of growing pigs is generally in the middle and early stage of growth, but generally not in the later stage.