For pork producers, mid-to-late March is really the time to start thinking about summer. A well-accepted fact of the business is that market-hog weights decline during summer months, although the amount varies somewhat due to location. For example, in the Iowa/Southern Minnesota market, which represents almost 44 percent of all market-hog sales, the average live-weight decline at slaughter for the past five years was 8.7 pounds from the January high to the August low. Carcass-weight declines were similar.

This loss in sale weight represents large income losses for production systems and producers. The current range for live-hog prices is $65 to $68 per hundredweight. As I write this, June through August lean-hog prices are trading at $98.50 per hundredweight. If I use a $2.50-per-hundredweight basis, this puts summer lean hogs at $96 per hundredweight, which translates to a live-hog price of $71 per hundredweight before any carcass merit is calculated.

If summer live-hog prices average $75 per hundredweight, then the lost weight of 8.7 pounds represents $6.52 less income per pig. The lower income is accompanied by the same fixed costs. The pigs weigh less due to slower rates of gain, as heat impacts performance, and the next group of pigs awaiting entry dictates the barn schedule.

This means the lost income really reflects a loss to the production system, since all expenses other than incremental feed use have already been paid by the pig. If feed conversion for the lost gain is 3.9, it represents 33.9 pounds of feed. The last diet is typically the cheapest in the finisher; if it costs $200 per ton, the lost gain represents $3.39 in feed savings.

Another way to sum that up is to suggest producers can afford to spend $3.13 per pig to get back the 8.7 pounds of lost weight. If summer hog prices exceed $75, they can afford to spend even more.

Research suggests that every 10 years growing pigs increase their heat output by about 15 percent. This is a function of genetic selection and management, both of which have resulted in much higher rates of lean gain. Data also is starting to suggest that one consequence of increased heat output is a decline in the upper-critical temperature. This means today’s growing pigs are more sensitive to excessive heat, and management strategies to help them deal with summer heat will increase gains.

You may have strategies to help alleviate the summer sales weight decline. Others just know sales weight drops in the summer and begin to modify their management once it starts.

Slaughter pigs that you’ll sell in June were weaned in mid-January and are already in grower facilities. Pigs weaned in early March will be placed in late April and early May and will be sold in August.

We think about summer and weight loss occurring because of July and August heat. But in recent years, the year’s high price has often occurred in mid-to-late May. So, it’s worth considering management strategies for pigs in your grow/finish facilities today that result in an increase in sale weight, which could have a huge financial impact on your income.

One management tool that’s often misapplied is wetting the pigs. I’ve seen producers who are so fearful of sick pigs that they refuse to wet them for evaporative cooling. I’ve seen producers and growers who won’t wet pigs in tunnel barns because they believe moving air over the pigs is cooling enough.

Wetting pigs correctly is one the more effective tools to provide heat relief. I generally recommend that controllers in curtain barns be set to wet pigs at 18° F above the set point. Sprinklers should provide large droplets (versus a fine mist) so that the pigs, not the air above them, are wet. Also 60 percent of the pen should get thoroughly wet in less than two minutes. Sprinklers on timers need to be kept on short intervals because during the wetting process the pigs’ blood vessels constrict in response to the cold water and heat loss declines. Cooling is maximized during the 15- to 30-minute drying period between wetting cycles via evaporative cooling.

Many producers and nutritionist are using fat in growing-pig diets, even at today’s price. Some nutritionists aggressively maintain high dietary energy levels for growing pigs since evidence suggests energy intake is the biggest limit on weight gain. Others add fat to all diets to reduce the metabolic heat load that limits feed intake in hot weather. Many also increase or begin using Paylean as a tool to maintain sales weight. Visit with your nutritionist about these and other dietary management tools that could pay off if timed correctly.