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Checklist to Reduce Heat Stress on Sows and Gilts

As the temperatures rise in summer, sow’s body temperature will increase, too, usually causing a drop in feed intake, especially during lactation. Lower feed intake causes sows to lose extra body weight, which can affect pig weaning weights, days to estrus after weaning, farrowing rate and subsequent litter size.

As the temperatures rise in summer, sow’s body temperature will increase, too, usually causing a drop in feed intake, especially during lactation. Lower feed intake causes sows to lose extra body weight, which can affect pig weaning weights, days to estrus after weaning, farrowing rate and subsequent litter size.

Because hogs have no sweat glands to cool themselves, we add extra stir fans, water drippers or cool cells in gestation and farrowing rooms to reduce the heat stress on sows and gilts.

A sow’s normal body temperature is 100-103o F. They prefer an environmental temperature at 80o F or less, which is their thermo-neutral temperature.

Two factors influence the effective environmental temperature (EET) of a hog – relative humidity and air temperature. These measures can help create a “heat index” that can be used to determine the temperature settings for cooling systems. The attached heat index chart (Table 1) shows how a change in relative humidity or air temperature can change a sow’s EET.

Following is a checklist of areas that can help reduce the effects of heat on the breeding females:

Semen and breeding management:

• High/low temperatures inside semen storage coolers should be charted daily. To get a more accurate reading, the high/low temperature probe can be placed in a bottle of water, so opening the cooler lid/door does not affect the readings.

• Keep the room temperature where semen is stored near 70 o F. to avoid overtaxing the semen storage cooler.

• When semen is delivered, check the temperature of bags on the perimeter and in the center of the container for hot spots. Record this information for follow up if a conception problem occurs.

• Review with your semen or extender supplier the ideal storage temperature for semen delivered or processed on farm.

• Start breeding earlier in the morning, before the peak heat of the day.

• Boars used for estrous stimulation/detection should be used only 30-45 minutes to ensure adequate pheromones are available to stimulate breeding females.

• To increase sex drive and pheromone production of heat-check boars, allow them to breed a sow or be collected at least once or twice a week.

• During estrous detection, boars should be moving into the flow of air coming from the cool cells to reduce early exposure of sows or gilts.

• During breeding, expose small groups of females to boars and breed as soon as possible to reduce the time a sow is in standing reflex, waiting to be bred.

• Give weaned sows extra feed from weaning to breeding to reduce days to estrus and increase the potential for larger litters.

• To reduce time spent breeding, cross-train some workers in proper breeding procedures so they can help during peak breeding times.

• With veterinary consultation, consider injecting Parity 1 females with PG600 at weaning to help stimulate the hormone system and reduce days to estrus.

• In the gilt development area, provide supplemental cooling to keep their environmental temperature below 85 o F. to ensure they keep cycling.
Lactation management:

• Increase cooling by adding fans, drippers and/or cool cells.

• Control body condition of sows entering farrowing, so they are not over-conditioned during summer heat.

• Check flow rates of waterers, providing at least 2 quarts/minute; spend extra time training first-litter gilts to use waterers. In summer, lactating sows can drink 10 or more gallons of water per day.

• Develop plans to keep daily feed intakes up by feeding more frequently, providing an extra feeding in the evening when it is cooler, and/or add a hopper to lactation feeders to allow 24-hour, ad-lib feeding.

• Record and review daily feed intake records. If feed intake drops during periods of higher temperatures, reformulate diets to provide adequate energy and protein levels.

• Feed Parity-1 and low-feed-intake females a higher density diet.
Ventilation management:

• Clean all exhaust fan blades and shutters to remove dust build up. Be sure shutters are clean on both sides so they can open completely.

• Check attic insulation for water damage (from winter snows) and for settling. R-factor should be 30-35.

• Use the heat index chart (Table 1) to determine when cooling systems will be activated.

• Check and repair cool cells, drippers, stir fans, and exhaust fans before it gets too warm.

• Check cool cells for winter damage, blockage due to dirt and calcium buildup, and air leaks due to shifting of cool cells.

• Measure speed of air coming through the cool cell with an air flow meter. If the cell is working correctly, the minimum speed should be 420 ft./min.

• Record external air temperature and relative humidity to calculate the heat index and fine-tune the cooling system.

• Suggested set point to start cooling systems in farrowing is 78 o F. and 74-75 o F. in gestation. Use the heat index to fine-tune starting temperatures.

• When using stir fans and drippers, start the stir fan before turning on the drippers.
Spend some time getting ready for the summer heat, putting plans in place to manage sows and gilts during extended periods of warm temperatures.

Key Performance Indicators
Tables 2 and 3 (below) provide 52-week and 13-week rolling averages for key performance indicators (KPI) of breeding herd performance. These tables reflect the most current quarterly data available and are presented with each column. The KPI’s can be used as general guidelines to measure the productivity of your herd compared to the top 10% and top 25% of farms, the average performance for all farms, and the bottom 25% of farms in the SMS database.

If you have questions or comments about these columns, or if you have a specific performance measurement that you would like to see benchmarked in our database, please address them to: [email protected] or [email protected].

Click to view graphs.

Mark Rix and Ron Ketchem
Swine Management Services, LLC