Cool weather presents a completely different thermal environment challenge. Therefore the operator has to do a better job of managing the thermal environment in the building. An air speed of 30 feet per minute or less is recommended for nursery and growing pigs. Many confinement units have a couple of pens where one can measure air speeds at least 100 feet per minute in winter. Drafts lower feed efficiency through extra stress, extra feed energy requirement, and more health problems.
Air quality can impact feed efficiency.
Ammonia acts as a low-level stressor, robbing pigs of energy needed for growth. Keep room air velocities low in cool weather, because high air velocity picks up more ammonia from the manure pit or gutter surface. Farrowing and nursery rooms have the highest ammonia potential because the stored manure temperatures are highest in those. In partly slatted finishing buildings, keep the floors clean as possible, so that the pigs are not lying in wet manure. Ammonia tends to be highest in scraper-equipped rooms, followed by deep pit rooms, and lowest in gravity drain and pit recharge systems.