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.