How to create the right environmental conditions for growing-finishing pigs (Part 1)

Intensive @#@227@#@ production is carried out under high-density housed conditions, and the microclimate inside the pig house is the main environmental condition. The microclimate of a pig house includes: temperature, humidity, wind speed, gases, sound, and so on. These environmental factors all directly affect the weight gain rate, feed utilization rate and ultimately the economic benefits of pigs.

1. Suitable temperature and humidity Pigs have a poor ability to regulate their own body temperature; they have only very few sweat glands that can help regulate it in hot weather, and only very little hair coat to resist the cold of winter. Therefore, pig houses must have good heat insulation and warmth retention, and must be regulated with a ventilation system. Only when temperature and humidity are kept within a suitable range so that the pigs feel comfortable can high production performance be achieved. Conversely, whether too high or too low, it will cause stress responses in pigs and lead to adverse consequences. In addition, China has a vast territory, and the climate differs greatly between north and south, so creating the most suitable temperature and humidity conditions for the pig herd is very important for pig production.

Experimental research has proven that the optimal temperature for growing-finishing pigs is 20°C. When the temperature decreases, pigs are forced to eat more, and most of the energy intake is used for heat production rather than meat production. If the temperature is too high, the feed intake of pigs decreases. As the saying goes, "piglets fear cold, adult pigs fear heat," which shows that meat pigs of different body weights require different optimal temperatures. Research has proven that pigs with a live weight of 11-45 kg have an optimal temperature of 21°C, while pigs of 45-100 kg need 18°C, and pigs of 135-160 kg need 16°C.

When the outside environmental temperature is higher than 30°C, cooling measures should be taken: turn on the longitudinal exhaust ventilation system, spray cool water, or feed more green, juicy feed. When the temperature inside the house is too low, warmth retention measures should be taken to increase weight gain. In the cold season in northern regions, doors and windows should be sealed tightly to reduce the invasion of cold wind, and some bedding straw should be added appropriately. Adding plastic warm sheds to open-style pig houses can keep finishing pig houses between 11-18°C without affecting the weight gain of the pigs.

The effect of house temperature on growing-finishing pigs is related to humidity. The most suitable conditions for obtaining the highest daily weight gain are a temperature of 20°C and a relative humidity of 50%. Under the most suitable temperature conditions, the level of humidity has relatively little effect on weight gain and feed utilization rate. The level of humidity is related to other environmental factors and may cause disease, thereby indirectly affecting the rate of weight gain.

2. Ventilation and air exchange The ventilation and air exchange in a pig house are directly related to wind speed and ventilation volume. The level of ventilation speed has a certain effect on the daily weight gain and feed conversion rate of pigs. Some people conducted experiments with pigs weighing more than 40 kg, comparing the effects of different wind speeds on production performance at different air temperatures. When the air temperature exceeded 37.8°C, increasing the wind speed also decreased daily weight gain and increased feed consumption. When the air temperature was 4°C-19°C, exposure to drafty wind also reduced daily weight gain and increased feed consumption.

Growing-finishing pigs under intensive high-density rearing need ventilation and air exchange all year round, but in every season the contradiction between ventilation and warmth retention must be properly resolved. One must not pay attention only to warmth retention while ignoring ventilation and air exchange, as this will worsen the air hygiene conditions inside the house, reduce the weight gain of finishing pigs and increase feed consumption. In North China, turning on fans or opening south windows at noon and shutting off fans or closing windows at 3-4 p.m. can reduce humidity inside the house and increase fresh air. Enclosed finishing pig houses should maintain an inside temperature of 15-20°C and a relative humidity of 50%-75%; the air flow speed should be 0.2 m per second in winter, spring and autumn, and 1.0 m in summer; the air exchange volume per finishing pig per hour should be 45 cubic m in winter, 55 cubic m in spring and autumn, and 120 cubic m in summer.

3. Reasonable stocking density Excessive stocking density will obviously affect the production performance of pigs. It is generally believed that at least 0.1 sq m of floor area should be provided per 10 kg of body weight. The pen area that each pig should have at different growth stages (partially slatted floor) is: <25 kg, 0.25 sq m; 25-50 kg, 0.50 sq m; 50-75 kg, 0.70 sq m; and 75-100 kg, 0.85 sq m.

4. Suitable group size Under the condition of the same pen area per pig, different group sizes will also affect the rearing results. Some people compared the production performance of 8-16 pigs per pen with that of 16-32 pigs per pen and found that the former was clearly superior to the latter. Under housed conditions, the performance of smaller groups improved noticeably, because tail biting and fighting were reduced.

Rearing by original litter can avoid phenomena such as tail biting and fighting. The social order formed by original-litter pigs during the suckling period remains unchanged during the growing-finishing period, which is extremely beneficial to production. However, when the uniformity of the pig breed is somewhat poor, some weak pigs or low-body-weight pigs will inevitably appear. In this way, pigs similar in origin, body weight, constitution, temperament and feeding behavior are grouped together for rearing. The body weight difference among individuals in the same group of pigs must not be too large; at the piglet (early) stage, the body weight difference within the group should not exceed 2-3 kg. After grouping, the stability of the group should be maintained. Except for adjustments made because of disease, excessive body weight differences, or constitution too weak to be suitable for rearing in the group, the group should not be changed arbitrarily.

In addition, grouping and merging into pens should also be carried out at night, and management and training should be strengthened to avoid or reduce fighting and biting.