According to researchers at North Carolina State University, maintaining sow feed intake during the summer months is the most critical management step in reducing the impact of heat stress on seasonal infertility. Kevin Rozeboom, Todd See and Billy Flowers suggest a number of methods to sustain lactation feed intake when ambient temperatures and humidity climb.

Feed more often

Most producers who switch from feeding two times per day to three times per day experience a 10–15% improvement in sow feed intake. It is important to remember that, when you increase the frequency of feeding, you must decrease the amount that you feed each time. This strategy is successful because of the normal increase in body temperature that occurs after a sow consumes a meal. In theory, a smaller meal will not create as big an increase in body temperature because there will be less feed to be digested. As a result, this could be very helpful for sows whose body temperatures already may be elevated due to high ambient temperatures.

Keep feed fresh

Sows can be picky eaters. In warm conditions, feed is more likely to spoil, especially if it is a liquid feed or contains high levels of fat. Feeding more often and feeding slightly smaller meals is an excellent way to keep feed fresh.

Try liquid diets

Liquid feeding is a common practice to increase feed intake in growing pigs that also can be used during lactation. There have been varying levels of success with liquid feeding, but some reports suggest that sow feed intake has increased by as much as 15%.

Add fat to the diet

One way to make sure that sows are consuming enough energy, even though they are eating less, is to add fat to the lactation diet. Supplemental fat (7 to 10% animal or vegetable fat) will increase the energy content of the feed. Because sows are consuming less feed, dietary levels of essential vitamins and minerals will need to be increased to compensate for lower overall daily feed intakes.

Ensure water is always available

Water requirements increase with high ambient temperatures. Pigs will drink more than 50% more water when temperatures increase from 15°C to 35°C. The researchers suggest that nursing sows should consume 30–40 litres of water every day, while gestating sows need 12–20 litres. Flow rates are important or sows will get frustrated – ideally, the watering system should deliver two litres per minute, or at least a minimum of one litre per minute. Water temperature and quality are also important — pigs will consume almost double the quantity of cool water (10°C) as warm water (25°C).

The complete article, Management Practices to Reduce the Impact of Seasonal Infertility on Sow Herd Productivity, is available on North Carolina State University's website.