In order to obtain the best production performance,We must learn environmental control system in mechanical ventilation and natural ventilation., there are many type of environmental control system of piggery from simple to complex.Although each kind of ventilation system has its uniqueness in some ways,but each type has it’s worth mentioning that can provide a range of environmental conditions to ensure the best production performance and health to pigs.All the design and management of ventilation system must be suitable for the environmental,So that we can attainThe environmental conditions we need.
Feed intake is the principal security of pigs’ production performance.In addition to the genetics and nutrition,we need to design the hog house for promoting the independently of pig feed intake, reducing the hazards of staff,reducing the pig temperature stress and other environmental stress.Independent appetite affect by the size and the composition of the pig group,temperature environment(temperature,airflow velocity,humidity),feed slot and the area of each pig.We must analyze each kind of ventilation system and prepare provide the appropriate environment to pigs raise in it.This is prerequisite to the best production performance of pig and necessary to keep workers healthy.
Factors of temperature environment
Keep the temperature of hog house in the comfort zone of pigs and the appropriate relative humidity(Usually is 50% ~ 65%) is the two main functions of ventilation system.However, when we analyze the whole building system,we need to analyze how the pig change it,So that we can determine the effective environmental temperature.Effective environmental temperature is the actual temperature pigs in.Pigs emit the heat by four ways: conduction,convection,radiation and evaporation.
Conduction is heat transfer from one surface to another surface,accounted for 10% ~ 15% of pigs for total heat release.Conduction can affect the growth of the pig, because conduction affect pig comfort level.Dry cement board on dell can make the 5 ℃ lower than the room temperature. when the weather is cold,the main advantage of laid mat grass on the ground is increasing the effective temperature of 4 ℃ ~ 9 ℃.Specific higher depends on the size and weight of pigs.In this case,its OK to set the room temperature low.In contrast, in the room with cold and wet board, the room temperature need to set high to compensate the low effectively environmental temperature .
Convection is the heat transfer from an object to the surrounding air,Convection of pigs is as much as 35% of total heat dissipation.Convection is required in the hot weather conditions,But when the environment is cold and the wind speed is too high the convection is harmful.For example,convection can cause problems in poor maintenance of weaning and fattening pig house.In cold weather, get the wind speed should be controlled at the levels of less than 0.15 m/s.To bigger pigs,wind speed should be controlled at the levels of less than 0.20 m/s.The ground wind speed was influenced by wind speed through the port,counterblast, distance from wall to port,unexpected wind and so on.With improvement of ventilation rate, the speed of wind is usually increase. When you want to increase the rate of ventilation because of the high room temperature.The increase of ventilation vehicles is limited to don't make pigs feel cold.The high wind speed have an adverse effect on pigs.
Radiation is heat send out from pigs to the surrounding process of no direct contact with the pigs.Radiation heat usually account for about 30% of the total heat release.W need pay attention to the non-insulated surface just like cement wall and curtain.Especially for weaning pigs in a fattening pig house.
Evaporative cooling is advantageous in hot weather.Pigs can directly dissipate heat through the skin and dissipate the body heat by improving the breathing.As shown in table 1,The 1.5 meters per second wind speed can make the pig feeling 10 ℃ temperature decrease.But When the environment temperature too close to the body surface temperature,the convection heat dissipation through the surface will reduced considerably.At this moment,we not only need to improve the wind speed,but also need to assist to the evaporative cooling.We can achieve evaporative cooling by adopting the spray and wet curtain.
The design of the ventilation system
Ventilation is the key factors of deciding any pig enterprise success or not. Well designed and easy managing ventilation system can ensure the environmental conditions is benefit to pig production performance.The purpose of ventilation system is mixing the the fresh air with the old air in house through prearranged opening , bring the Heat, moisture and contaminants in air and discharging the damp air and contaminants out.The ventilation system and management way will affect the following conditions:
Moisture condensation on the surface of the object;
The evenness of the air temperature in house.
Wind speed blowing the pigs;
Smell in the air and the viscosity of the harmful gases.
Standard of dust and pathogenic microorganisms of inner air.
To accurately determine the performance of the ventilation system,we need to determine animal life zone from the ground to the air quality within the scope of 0.6 meters above the ground.The good ventilation of animals living area depends on the design of the ventilation system,management skill,management of investment,the layout in piggery,the layout of the farm buildings,construction technology,The correct application of heat insulation and the carefully of selected materials.
The ventilation rate of pig house need to change with the weather.In the most ventilation strategy,The volume of fresh air is depended on the temperature of inside and outside.When the weather is cold, warm and hot, the ventilation rate is different.The ventilation in the cold days need provide the enough oxygen and the ventilation for the decontamination. The ventilation in warm weather can change the temperature and increasing air flow and control the room temperature.the wind blowing pigs can achieve the cooling effect.This is improving the comfort of a pig by increasing air cooling effect.The ventilation in the hot days improve the speed of blowing wind and produce the cooling effect.
Three most common types ventilation system include:（1）full mechanical ventilation,(2) mechanical - natural comprehensive ventilation,（3）natural ventilation.Mechanical ventilation systems and can be divided into two types:the first type is use ventilator on the wall or under the cesspit of the floor,at the same time,setting the air inlet on the ceiling,It’s the traditional type.Another type also the traditional mechanical ventilation systems but it is adopt the longitudinal ventilation in summer.Mechanical - natural comprehensive ventilation is using the ventilator and the air port in some of the warm days and the cold days.And use the curtain on the side wall in the rest of the warm weather, and all the hot weather.Natural ventilation system is using the principle of wind and the floatation of hot air for the animals living area.The need of ventilation car change at different stages of big,it makes the design of the ventilation system become the challenging.
Mechanical ventilation system include the exhaust fan,the ceiling air inlet,heater and controller in cold weather.the design of fan for animals must made by the credibility manufacturers,we should choose the fan that can meet the following standard when the fun run under the full speed condition:
Design air supply rate can resist 25～31 pascal static pressure.
Airflow comply with the design standards.
To be able to run continuously.
Adopt the closed circuit.
Can run under the all sorts of airflow condition.
Tolerated and discharge rust and dust in the air。
Through test of qualification testing agencies。
In order to ensure the air can be mixed evenly as planned,must make the air appropriate distribution in the piggery in order to keep maintain proper airflow.As for eliminate blind angle and limit the undesirable evil wind.There are many different types of air inlet.There is the continuous air inlet with the ceiling of the airway,the self-adjusting ceiling air inlet(including one-way,both way,four directional,statements of air inlet),wall air inlet preheat through the aisle or sidewall inlet directly intake from the outside world and the opening of wind curtain.Each inlet design have their advantages and disadvantages,but its position and operation should be able to make the fresh air was sent to all the pigs and have a proper wind speed in the standard of pigs. It may occur a problem here, the position of each inlet get too close thus maybe produce reverse flow.So,two direction of air flow can touch each other and produce downward flow.It will result that too much air blowing the pig.We must set up the sufficient number of port so that fresh air can be distributed throughout the house and the capacity of the air intake to match with the capacity of the fan.The port which matched with the speed 3．5～5m/s of outlet will produce 10 ~ 18 of static pressure inside.
The controller we choose must be sensitive and matched with its ventilation system. It also need to be well-adapted, easy to use,reliable and accurate, easily maintained and durable service.Among them, one of the key characteristics should be simple and easy to use.Many controller has a lot of functions, but pig breeders feel complex.