Summer weather is upon us, with all the misery that comes with it for many of our production facilities. I’ve been doing quite a few meetings and presentations these past weeks with industry supplier sales forces and producer groups regarding recommended management practices for summer heat in production facilities.

This week it is predicted to be in the low 90’s with dew points approaching 70 in southern Minnesota so we know it will be hot in our grow-finish units. As I do site visits and do the training meetings for producers and allied industry, I continue to meet people who don’t understand the impact of heat on growing finishing pigs. The week of July 18 in the upper Midwest last year had a major impact on sale weights. The 5 year average for barrow and gilt sale weight decline from January to mid-July is 8.7 pounds. Last year the decline was 11.2 pounds.

The decline is directly related to the success of production managers in helping growing pigs stay cool so that feed intake doesn’t decline too much. A common falsehood that I come across is that because today’s pigs are so lean with limited backfat, they are better able to cope with hot weather as there is less ‘insulation’ to hold heat in the pig.

In fact the opposite is true. Because today’s genetics have such high rates of lean gain compared to previous generations of pigs, their ability to deal with hot weather is less. There is good evidence that today’s genetics have higher levels of heat output (as much as a 10-15% increase in total heat output every 10 years). There is also mounting evidence that because of this higher heat output associated with the higher rates of lean gain the pig has a lower upper critical temperature. This means that the pig becomes hot and adapts mechanisms to deal with excess heat at lower temperatures than much of the scientific literature would suggest.

Data from the Netherlands in the early 2000’s suggests that 132 lb pigs on partial slats begin to reduce feed intake at 78F. Yet I continue to run into producers and allied industry advisors that don’t want to provide drippers/wetting of pigs until at least 85-90F because it might ‘stress’ the growing pig.

I also get into quite a few tunnel ventilated barns that have no provision for wetting of pigs. The owners believe that the high rates of air movement (often above 400 fpm) will be sufficient. This can’t happen. A pig’s surface temperature is approximately 95F. When 90-95F blows over 95F skin, not much heat transfer can occur unless the skin is wet and evaporative cooling occurs.

Since the pig can’t sweat it is our responsibility to provide water to the skin of the pig for effective evaporative cooling. The available data suggests that big droplets that thoroughly wet the skin are more effective than fine mists that cool the air above the pig. In addition, big droplets don’t ‘drift’ as much and are less prone to result in wet feed in feeders and’ green grass’ on the north side of curtain barns.

The basic recommendation remains to use big enough nozzles to wet approximately 60% of the pen in under 2 minutes and then turn off the nozzles for a 15-30 minute drying period. I recommend that curtain barns begin this process at 18F above the controller set point and that tunnel barns start at 20F above.