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What effect does light have on the growth and health of pigs

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Lighting in pig houses can be divided into natural lighting and artificial lighting according to the light source. Natural lighting refers to direct sunlight and scattered light entering the pig house through light-transmitting structures such as doors and windows for illumination. In the solar spectrum, visible light accounts for 50%, and most of the remaining 50% is infrared light, with a small amount being ultraviolet light. Natural lighting in a pig house is generally expressed as the ratio of the total light-transmitting area of the pig house to the floor area inside the house, which is called the lighting coefficient. Artificial lighting uses artificial light sources (incandescent lamps or fluorescent lamps, etc.) for illumination. In the spectrum of incandescent lamps, infrared accounts for 60%

Lighting in pig houses can be divided into natural lighting and artificial lighting according to the light source. Natural lighting refers to direct sunlight and scattered light entering the pig house through light-transmitting structures such as doors and windows for illumination. In the solar spectrum, visible light accounts for 50%, and most of the remaining 50% is infrared light, with a small amount being ultraviolet light. Natural lighting in a pig house is generally expressed as the ratio of the total light-transmitting area of the pig house to the floor area inside the house, which is called the lighting coefficient. Artificial lighting uses artificial light sources (incandescent lamps or fluorescent lamps, etc.) for illumination. In the spectrum of incandescent lamps, infrared accounts for 60%-90%, visible light accounts for 10%-40%, and there is a small amount of ultraviolet light; fluorescent lamps are similar to sunlight, and their light output is 3 times that of incandescent lamps of the same power, but the application cost is high, so incandescent lamps are used more in production.

The intensity and duration of light have a certain effect on the productivity and health of pigs. The effects of infrared rays, which have thermal radiation effects, and part of visible light on pigs have been discussed in the previous section. The following mainly discusses the effects of light intensity and duration on pigs.

Suitable lighting can promote the deposition of protein, fat and minerals in the body, which is beneficial to growth; it can also increase the secretion of sex hormones, strengthen ovarian and testicular function, and improve the reproductive capacity of pigs. Appropriately extending the duration of light can promote sexual maturity in pigs, and appropriately extending the duration and intensity of light can promote estrus, mating and pregnancy in sows. Insufficient or excessive light is harmful to the productivity and health of pigs. Too short or too dim light can reduce the secretion and activity of digestive juices in pigs and reduce appetite; too strong and too long light strengthens body metabolism, increases activity, and increases energy consumption, thereby affecting weight gain. For example, test pigs with an illuminance of 5 lx had an average daily gain 5.7% lower than control pigs at 40 lx; while test pigs with an illuminance of 120 lx had an average daily gain 13.8% lower than control pigs at 50 lx. Giving lean-type pigs appropriately stronger and longer light can increase their carcass lean percentage, while giving fat-type pigs relatively weaker and shorter light is beneficial to weight gain.

Appropriate ultraviolet irradiation can ensure normal calcium and phosphorus metabolism in the pig body, promote bone growth and development, and has the function of preventing and treating rickets. Ultraviolet rays also have the effect of promoting metabolism in the body, thereby improving the productivity and feed conversion rate of pigs. Ultraviolet rays also have effects such as killing bacteria, viruses and fungi and destroying certain toxins (such as tetanus toxin), and have effects such as enhancing the bactericidal power of the blood and immunity. However, excessive ultraviolet irradiation (such as strong sunlight in summer) can also cause dermatitis in pigs (especially white pigs), keratitis and conjunctivitis, and in severe cases can act on the central nervous system, causing symptoms such as dizziness and headache. Visible light can cause a series of neural and endocrine changes in the body, affecting the pig's feeding, drinking, daily activity patterns, metabolic function, growth and development, sexual function and resistance.

II. The impact of noise on pigs

Noise refers to sound that can cause unpleasant and uneasy feelings or harmful effects. The intensity of noise is generally expressed as sound pressure level, with the unit being decibel (dB). The noise in a pig house should not exceed 75 dB.

In livestock production, the main sources of noise include: noise introduced from outside the house, such as the sound of cars and tractors starting, and the sounds of strong wind, thunderstorms, etc.; noise generated inside the house, including that produced by the operation of mechanical equipment, such as the sound of fans; and that produced by feeding and management activities, such as the sound of shovels scraping against concrete floors; in addition, activities such as pig vocalizations, fighting and feeding also produce relatively strong noise. Sound enters the brain through the auditory organ, the ear, causing neural and endocrine activity and affecting behavior, metabolic intensity and various life activities. Beautiful and pleasant music can excite the nerves, stimulate appetite and improve metabolic function, just as people feel relaxed and happy when listening to music. Noise will affect the pig herd, but because pigs are slow to respond to sound, noise has little effect on them.

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