Pigs in Hot Weather: Address Summer Feed Consumption Decreases in Sows

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Purina Animal Nutrition

Heat stress is a seasonal challenge that can be detrimental to sow productivity.

Swine producers must face the challenge of pigs in heat head-on every year. Sows that suffer from heat stress have a greater potential to experience seasonal infertility, smaller litter sizes, decreased embryo survival rates and death losses.1 These issues may be a result of decreased feed consumption, commonly resulting from heat stress.
Sows can begin to feel heat stressed as temperatures surpass 70ºF, depending upon humidity. Sows are most comfortable between 45º and 70ºF; the range of 60º to 65ºF is optimal for lactating sows.2 As temperatures increase outside of this range of comfort and humidity levels exceed 40 percent relative humidity, feed consumption can begin to decrease.
Temperature and humidity cause stress to the animal. The combination of these two numbers is known as the Temperature-Humidity Index (THI). THI levels can provide insights to the level of heat stress risk for sows. 
In addition to using the THI index, monitoring a sow’s resting respiration rate can be a good indicator if the animal is experiencing stress. Count the number of times the rib cage moves in and out in a 60-second period. Normal respiration rates are between 15 and 25 breaths per minute. When respiration rates exceed 40 breaths per minute, the pigs are at risk of heat stress.
Environmental controls can help adjust the temperature in the facility; however, adjustments in the sow’s ration should also be implemented to avoid decreased feed consumption.
Nutrition and management tips to promote summer productivity include:
Nutrition tips
1. Promote consistent feed consumption. Help sows maintain a body condition score (BCS) of 3 on a 5-point scale through consistent feed consumption. Incorporate a summer feed additive into the diet, such as True Appetizer® feed from Purina Animal Nutrition, to address summer consumption decreases.
2. Feed nutrient-dense diets. Feed a palatable, concentrated source of energy to sows to compensate for reduced intake that is formulated correctly based on energy concentration of the lactation diet. A dense source of energy, fed with a summer sow feed additive, can help the sow consume the nutrients needed to support milk production and maintain body condition.
3. Feed sows according to stage. BCS is important for all sows, so an ad libitum ration is suggested during lactation with limit-feeding during gestation. Feed sows to maintain condition during gestation as overconditioned sows at farrowing may consume less in lactation. Overconditioned sows also have more stress potential during hot weather.
4. Lactation feed intake is critical as sows need greater nutrient levels. Pearson recommends adjusting lactation rations in the summer to help sows receive the nutrients needed to maintain condition.
5. Increase feeding frequency. Feed sows smaller meals, more times throughout the day to decrease the heat generated when breaking down the feed. A sow’s body temperature will increase less if she consumes 4.5 pounds of feed vs. 6 pounds.
Switching from two large meals to three small meals can increase sow feed intake 10 to 15 percent. Account for this additional feed when making ration changes.
6. Provide calories through fat vs. fiber. Include higher levels of fat, such as tallow, choice white grease or vegetable oil at 2 to 6% of the diet. Fat increases caloric density while reducing the amount of heat generated during digestion.
Management tips 
1. Manage water carefully. Keep sows hydrated through a quality water source. Adjust and test waterers to ensure proper flow rate and accessibility. An increase in air temperature from 54º to 60ºF to 86º to 95ºF can cause sows to drink more than 50 percent more water. Lactating sows drink 8 to10 gallons of water daily, which can double as THI levels increase.
2. Provide an adequate water-to-feed ratio. A general rule is to maintain a water-to-feed ratio of 5:1. Provide water near 50ºF for optimal consumption.
3. Maintain ventilation and cooling systems. Provide adequate air movement in the facility. Minimum enclosed facility ventilation rates during the summer months are: sow and litter: 500 cubic feet per minute (CFMs); gestating sow: 180 CFMs; and breeding sows: 300 CFMs. Test the ventilation system to ensure these rates are met.
Strategies including fresh air inlets, cool cells, nose coolers, sprinkler systems and drip coolers can also be implemented to provide cooling.
If utilized, move heat lamps for piglets away from the sow’s head or discontinue use during warm periods, if appropriate.
4. Schedule animal activities during the coolest parts of the day. Allow sows to relax during warm periods by only moving or working with sows in the early morning and evening.
5. Keep feed fresh. Sows can be picky eaters, and in warm temperatures, feed is more likely to spoil. Increase feeding frequency, feed slightly smaller meals and routinely clean the feeding area to keep feed fresh through the summer.
Based on ventilation, stocking rate, humidity and weight of the sow, temperatures at 70ºF and up can start to affect feed intake. 
Because of factors outside of Purina Animal Nutrition LLC’s control, individual results to be obtained, including but not limited to: financial performance, animal condition, health or performance cannot be predicted or guaranteed by Purina Animal Nutrition LLC.

1 Rozeboom, K.J., M. Todd See and W. Flowers. “Management practices to reduce the impact of seasonal infertility on sow herd productivity.” North Carolina Cooperative Extension Service. Publication No. ANS00-8138. http://www.ncsu.edu/project/swine_extension/publications/factsheets/813s.htm. 5 May 2013.

2 Whitney, Mark. “Minimizing heat stress in pigs during the summer.” University of Minnesota Extension. http://www.extension.umn.edu/swine/components/pubs/Whitney-MinimizingHeatStress.pdf. 5 May 2013