来源：The Pig Site
Winter is here. Are your barns ready?
The temperatures are dropping and the first snow has already accumulated in parts of the world. It can be challenging to keep pigs comfortable under winter conditions. Maintaining optimal barn conditions is important for animal wellbeing, farm productivity and people working in the barn. Good ventilation will remove humidity, dust, gases and it will provide fresh air.
PIC has observed lower respiratory challenges, lower mortality and higher feed intake in barns with optimal conditions versus barns with suboptimal conditions. The right ventilation strategy can make the difference. This article will review tips and tricks around ventilation management that PIC has developed over time in collaboration with many of its customers.
In the winter, there is a fine line between providing good air quality and comfort for the pigs. Too much cold air intake could lower pig activity resulting in decreased feed intake. In addition, too much cold air also leads to higher energy costs.
On the other hand, insufficient ventilation can lead to damp barns which can cause respiratory challenges and increased mortality. Dampness will also lead to degradation of the ceiling, roof and equipment.
The core premise of good ventilation management is that air exchange and temperature should be managed separately. Good ventilation practices are to maintain a minimum ventilation rate while optimising the air flow in the farms to reduce energy losses. Specifically two practices have to be combined:
· Minimum ventilation – the ventilation system is operating at the minimum setting when the room temperature falls below the set point. Table 2 shows the PIC minimum ventilation recommendation by pig. This minimum ventilation setting ensures sufficient air exchange.
1. 最低通风率 - 当室温低于设定值时，通风系统以最小设置值运行。表1为PIC的最低通风率建议。该设置可确保充分换气。
· Role of inlets – the correct settings for inlets help to achieve adequate air velocity across the ceiling of the barn and mixes cold air with warm air in the room before reaching pig level. Since cold air is typically denser than warm air it will start to fall faster than warm air. The goal of minimum ventilation is to mix cold outside air with warmer barn air. Proper mixing of air can be achieved through the correct air velocity .
This approach avoids producing a draft on top of the pigs and achieves an optimal air exchange. In addition it is important to match the inlet opening to the number of fans. Inlet openings that are too tight could result in freezing inlets and poor air mixing – which can result in chilled pigs, wet floors and increased energy costs.
With these concepts in mind, we would like to share some practical ventilation tips that help you prepare your barns for the winter:
2. 入风口的作用 – 正确安装入风口有利于空气充分流动，使上层冷空气在被猪群吸入之前，先与室内的暖空气中和。冷空气通常比暖空气更密集，因此会比热空气下沉得更快。设置最低通风率是为了将外部的冷空气与猪场内较暖的空气混合。合适的空气流速可以让空气更好地混合。此外，入风口的开口与风扇数量相匹配也很重要。开口过紧可能导致入风口结冰、空气混合不良 - 这可能导致猪群受冻、地板受潮，消耗更多能量。
· Ensure that all fans are clean following fall pumping season and ensure pump out covers are in place and sealed. Dirty louvers and fan blades may decrease fan efficiency by as much as 30 percent. Consider covering wall fans that will not be used during the fall and winter with plastic wrap to provide insulation and avoid stray cold air entering the barn;
· Clean temperature and brooder probes and ensure accuracy of reading. Place probes in spots that give accurate temperature reading and avoid placing them directly in front of inlets;
· Consider using bubble wrap in curtains to provide insulation to the room. Be sure to leave a gap of 10-12 inches at the top of the curtain to provide room for air to enter the building；
· Review minimum ventilation variable fan speeds and inlet openings to achieve a minimum of 600-800 FPM and less than 65 percent relative humidity;
6. 检查最小通风量、风扇速度和入风口开口，以达到最低600-800 FPM和低于65％的相对湿度;
· Variable speed fans should not run below 50 percent on the controller, otherwise these fans could be in jeopardy of needing frequent maintenance or freezing up;
· Adjust temperature bandwidth on the controllers, stage-to-stage, in winter time to approximately 1.5–2.0°F;
· Avoid heater overshoot. PIC recommends 2°F heater off-set below the set point. (For example, if the set point is 75°F, the heaters turn on at 72°F and off at 73°F);
9. 避免加热器超调。PIC建议在设定点以下2°F关闭加热器。 （例如，如果设定点为75°F，则加热器在72°F开启，在73°F关闭）;
· When using brooders and/or mats, comfort zones should be at 95°F directly beneath the brooder for 14-21 days, dependent on pig size and health. Additionally, pigs require 0.4 square feet of mat space to help maximise pig comfort and eliminate drafting from below the slats or plastic flooring;
· Consider adding fan cones to improve a fan’s CFM output by 10-20%.
While winter continues to be a challenge, it is also an opportunity for continuous improvement. By following the ventilation best practices, pig comfort can be increased over the long winter months. Striking a balance between ventilation and temperature will provide the best possible way to optimise barn conditions to help your farm reach its full potential.
Table 1- Minimum Ventilation Recommendations