It’s the season for producer meetings and I’ve already spoken with many producer groups and production system growers this winter. Another round of meetings begins again tomorrow.
At the previous meetings this winter I’ve been asked to spend time on common winter ventilation mistakes and my version of a grower’s daily chore routine. With 60F expected in southern Minnesota today and the prospects of field work beginning in a few weeks for many clients, common winter ventilation mistakes doesn’t make sense as a topic.
Instead, I’m spending time talking about summer cooling strategies. Seems funny to talk about summer heat when we had -10F for a low last week, but our first really hot days often occur when producers are busy with field work. Thus, now is the time to review your sprinkler and stir fan strategies and controller settings to accomplish these strategies.
As I’ve often discussed in this blog, because of the very rapid rates of lean deposition in late finishing, today’s pigs generate more heat that previous generations of pigs and as a consequence are more sensitive to hot conditions in their facilities. In addition, I continue to encounter producers who believe that blowing air (stir fans or tunnel barns) is adequate heat relief for growing pigs.
The skin temperature on a growing pig is approximately 95F. If we blow 90F air across the 95F skin surface, minimal heat exchange takes place as there is only a 5F differential in temperature. That is why the addition of water for evaporation is so critical to keeping pigs growing in warm/hot weather.
For every 1 lb of water evaporated from the surface of a pig, the pig loses 1044 Btu of heat. This is a big number when we consider that a market weight pig is producing somewhere between 1000-1200 Btu/hr of heat. To accomplish this cooling, I recommend that sprinklers (not misters) be set to turn on at 18-20F above set point, assuming set point is lowered to 60-62F in late finishing.
Sprinklers should be installed to wet approximately 50-60% of the pen area. Because a good part of a pen is not wetted during the sprinkling process, I’m not afraid to start sprinkling pigs if necessary when they are 60-80 lb (set point in the controller of 66-68F so sprinkling begins 86-88F). Smaller pigs will reduce feed intake and have growth depression from excess heat just as much as big pigs, just at a higher temperature.
Use large droplet size sprinkler nozzles/devices. Nozzles that result in fine mists of water above the pig cool the air above the pig and wet the hair tips of the pigs, not the skin of the pig. Cooling isn’t as effective, and the fine mist tends to drift in air currents.
Only leave the sprinkler on long enough to thoroughly wet the furthest pen of pigs from the solenoid. Pigs vaso-constrict during the application of the water so minimal cooling occurs. The cooling occurs during the evaporation of the applied water during the 15-20 minute off time of the cooling cycle.
Properly done, sprinkling of pigs on warm/hot days can make a significant difference in feed intake and daily gain for all ages of growing pigs.