Effect of Light on Pigs

The light of piggery can be divided into natural light and artificial light according to different light sources. Natural illumination means that direct and scattered light from the sun enter the pig house through transparent structures such as doors and windows. Visible light accounts for 50% of the solar spectrum, and the remaining 50% is mostly infrared light and a small amount is ultraviolet light. The natural light of the pig house is generally expressed by the ratio of the total area of the pig house that can be transparent to the ground area of the house, which is called the lighting coefficient. Artificial lighting is illuminated by artificial light sources (incandescent or fluorescent lamps, etc.). In the spectrum of incandescent lamp, infrared accounts for 60%, visible light accounts for 10%, 40%, and there is a small amount of ultraviolet; fluorescent lamp is similar to sunlight, its luminous amount is 3 times that of incandescent lamp of the same power, but the application cost is high, so incandescent lamp is used more in production.

The intensity and time of light have a certain effect on the productivity and health of pigs. The effects of infrared and partial visible light with thermal radiation on pigs have been discussed in the previous section, and the effects of light intensity and time on pigs are discussed below.

Suitable light can deposit protein, fat and minerals in the body, which is beneficial to growth, increase the secretion of sex hormones, strengthen the function of ovary and testis, and improve the reproductive ability of pigs. The proper extension of light time can promote the sexual maturity of pigs, and the appropriate extension of light time and intensity can promote estrus, mating and pregnancy of sows. Insufficient or excessive light is disadvantageous to the productivity and health of pigs, too short or too dark light time can reduce the secretion and activity of digestive juice and loss of appetite; too strong and long light can strengthen the metabolism, activity and energy consumption of the body, and affect weight gain. For example, the average daily gain of 5lx pigs was 5.7% lower than that of 40lx control pigs, while that of 120lx pigs was 13.8% lower than that of 50lx control pigs. Lean pigs with appropriate strong and long light can increase their carcass lean percentage, while fat pigs with relatively weak and short light are beneficial to weight gain.

Proper ultraviolet irradiation can ensure the normal metabolism of calcium and phosphorus, promote the growth and development of bones, prevent and cure rickets, and promote metabolism in the body, so as to improve the productivity and feed conversion rate of pigs. Ultraviolet rays also have the function of killing bacteria, viruses, fungi and destroying some toxins (such as tetanus toxin), and can enhance blood bactericidal power and immunity. However, excessive ultraviolet radiation (such as strong sunlight in summer) can also cause dermatitis (especially white pigs), cornea and conjunctivitis in pigs, which can act on the central nervous system and cause symptoms such as dizziness and headache. Visible light can cause a series of nervous and endocrine changes in the body, affecting feeding and drinking water, diurnal activity, metabolic function, growth and development, sexual function and resistance of pigs.

Second, the effect of noise on pigs

Noise is a sound that can cause unpleasant and uneasy feelings or harmful effects. The intensity of noise is generally expressed by the sound pressure level, in decibels (dB). The noise in the pigsty should not exceed 75dB.

In animal husbandry production, the main sources of noise are: noise from outside the house, such as the sound of cars and tractors, strong winds, thunderstorms, etc.; the noise generated in the house, including the operation of machinery and equipment, such as the sound of fans; there are also noise generated by feeding and management activities, such as shovel and cement ground friction; in addition, pig singing, fighting, feeding and other activities also produce strong noise. Sound is transmitted into the brain through the ear of auditory organs, causing neural and endocrine activities, affecting behavior, metabolic intensity and various life activities. Beautiful music can excite nerves, stimulate appetite and improve metabolic function, just like people who listen to music in a good mood. Noise will affect pigs, but because pigs are slow to respond to sound, noise has little effect on them.