How important is the rearing environment in chicken farming?
With the deepening of agricultural industrial structure adjustment and the internal structural adjustment of the livestock industry, the construction of breeding communities has developed rapidly, but because most poultry farmers do not have sufficient understanding of the rearing environment for chickens, the rearing efficiency of chickens is relatively poor. Several key issues in broiler rearing are briefly discussed below.
1 The harm of poor ventilation
Because broilers grow quickly, have vigorous metabolism, and are raised at high density, as the chickens continue to grow, the amount of fresh air needed increases more and more, more and more feces are excreted, and more and more harmful gases are produced. Among them, the gases most harmful to chickens are mainly ammonia and hydrogen sulfide.
Ammonia is a colorless gas with a strong irritating odor and a low specific gravity. In a warm house it generally rises to the roof, but because ammonia is produced on the ground and around the chickens, its content at the floor level of the chicken house is also relatively high, especially when the chicken house is humid and poorly ventilated, when the ammonia concentration inside is even higher. Chickens are especially sensitive to ammonia, which has an irritating effect on their mucous membranes and can cause hyperemia and edema of the conjunctiva and upper respiratory tract mucosa. Pathogens take the opportunity to spread through the upper respiratory tract and lungs to the thoracic air sacs and abdominal air sacs. After causing respiratory diseases in chickens, feed intake decreases, which not only affects the growth and development of the chickens but also reduces their resistance to disease. The incidence of chicken Gambaro disease and Mycoplasma gallisepticum disease increases, and production performance is greatly reduced. At the same time, because there is no diaphragm between the thoracic and abdominal cavities of chickens, after chickens develop respiratory diseases, secondary digestive tract infection can occur, causing Escherichia coli disease in chickens, thereby significantly increasing the mortality rate of chickens. Therefore, the ammonia concentration in the chicken house generally should not exceed 0.015%.
Hydrogen sulfide is a colorless, flammable gas with a special rotten-egg odor, and it is irritating and suffocating. It is produced from the ground, and because its specific gravity is high, the closer to the ground, the greater the concentration. Long-term poisoning by low concentrations of hydrogen sulfide can cause decline in the chickens' physical condition, reduced resistance, listlessness, poor appetite, and decreased production performance; high concentrations of hydrogen sulfide can cause paralysis of the respiratory center and death. Therefore, the hydrogen sulfide concentration in the chicken house generally should not exceed 0.5%.
2 Measures to maintain good air in the chicken house
2.1 Ventilation and air exchange. On the premise of ensuring a suitable temperature, try as much as possible to ensure ventilation and air exchange in the chicken house. The principles to grasp are: windows and doors should be opened slightly in the morning and evening when it is cool, opened wide at noon when it is hot, opened slightly when it is windy, and opened wide when there is no wind. This should be done gradually, and all windows and doors must not be opened fully during ventilation. When entering the chicken house and the smell is pungent, ventilation must be opened up and the indoor temperature raised. In the early stage of rearing, heat preservation is the main focus, and exhaust fans should be used while also providing ventilation; in the later stage, ventilation is the main focus while also providing heat preservation.
2.2 Strengthen sanitation management of the chicken house. When feces decompose under anaerobic conditions, harmful gases are formed. Therefore, feces must be removed promptly once a day to increase air circulation and reduce the production of harmful gases. The relative humidity of the air in the chicken house should be maintained at 55%-70%. If it exceeds 80%, ventilation should be strengthened, or some quicklime should be placed on the ground to absorb moisture. Manage the chickens' drinking water well and avoid overflow or leakage from drinkers. Prevent chickens from having watery feces in order to slow down the fermentation rate of feces.
3 Other rearing environment requirements
3.1 Temperature. The first aspect of the rearing environment in a chicken house is temperature. Different types and ages of chickens have different ideal temperature ranges. In general, the optimum temperature for laying hens is 24-27°C, the optimum temperature for broilers is 1-22°C, and newly hatched chicks need a temperature of 32-34°C. Afterward, as the age in weeks increases, the temperature gradually decreases, that is, for each increase of 1 week of age, the temperature decreases by about 2°C. By the 6th week of age, it is appropriate to keep the temperature at 22-24°C. Within a certain temperature range, the laying rate will decrease as the temperature rises. The suitable temperature for laying by adult chickens is 13-22°C, and the temperature at which the laying rate is highest is 1.5-18°C.
3.2 Humidity. The suitable relative humidity required for chicks is 60%-75%, and for adult chickens it is 60%-65%. Within this relative humidity range, the laying rate of adult chickens is highest. Under suitable relative humidity conditions, chickens appear energetic, their feathers are clean and glossy, disease resistance is enhanced, and the laying rate increases.
3.3 Lighting. Generally it is natural lighting, and there is also electric lighting. Both appropriate light levels can promote bone growth and accelerate the growth and development rate of chickens. At different stages of growth and development, chickens have different requirements for photoperiod and light intensity: during the first 5 days after hatching, chickens need 24-hour lighting, with a light intensity of 5-10 LX (lux), and lighting with a 25W or 40W bulb is sufficient. Afterward, as the age in days increases, the photoperiod should gradually decrease, by 1.5-2 hours per day, and by the 20th day 8 hours of lighting is sufficient. After 18 weeks of age, near the laying period, the photoperiod should gradually increase, and the most suitable photoperiod for laying is 17-18 hours. Therefore, during the laying period of chickens, artificial light sources must be used before sunrise and after sunset to supplement the photoperiod in order to increase the laying rate. Light quality is also important. In particular, red light and infrared light stimulate the chicken's pituitary gland through vision, increase hormone secretion, strengthen the vitality of the reproductive system, and can increase the laying rate.