By Matt Romoser, Iowa State University Extension and Outreach swine field specialist
With warm weather arriving, a predictable drop in sow fertility will soon be observed across the swine industry’s breeding herd. Heat stress is a multimillion-dollar problem for all stages of pork production, and negatively affects multiple key performance indicators for sow farms, including:
- Delayed puberty onset in gilts
- Prolonged wean to estrus interval
- Lower conception and farrowing rates
- Reduced litter size
Elevated temperatures and associated heat stress is thought to be the primary driver of seasonal infertility given the direct and cumulative impact of higher ambient temperatures on lost productivity. Changes in photoperiod (reduced daylight hours from summer to fall) is also a likely factor in observed reduced fertility. The following recommendations are intended to maximize reproductive performance during periods of seasonal infertility.
Maintaining a comfortable environment
It goes without saying, optimizing the environment for the sow is the foremost intervention to address seasonal infertility. A recent Iowa Pork Industry Center publication on heat stress in the breeding herd provides an in-depth summary of environmental considerations.
Some areas of importance to continually monitor include:
- Properly maintaining evaporative cool cell and system
- Monitoring ventilation rates for breeding, gestation and lactation (250 to 700 cubic feet per minute (cfm) per sow).
- Monitoring drip cooling or sprinkler systems for flow rate as well as on-off settings to allow for evaporation.
- Managing zone heated areas to warm piglets while attempting to minimize potential impact on sow body temperature.
- Managing lighting in breeding areas to be consistent at 16 hours on, 8 hours off with a minimum of 200 to 250 lux intensity
Maximizing feed intake
A drop in feed intake is one of the hallmark physical responses of pigs exposed to higher ambient temperatures. This of course creates a challenging dynamic for the lactating sow, particularly first parity, where high energy demands of lactation and reduced feed intake potentially puts her in a negative energy balance at weaning.
Some general considerations for farms include:
- Cleaning wet or spoiled feed from feeder daily.
- Feeding small meals more frequently in lactation may help increase intake and minimize wastage.
- Reducing fiber and adjusting nutrient density may help reduce metabolic heat production and combat lower feed intake.
- Checking drinkers for adequate water flow rates in lactation and gestation.
- Increasing feed allotment to 6 to 8 pounds in weaned sows for farms with prolonged wean to estrus interval (WEI).
- Closely monitoring mycotoxin levels, particularly zearalenone, as potential exposure is greater when feeding old crop corn in late summer early fall.
Reproductive management
Ultimately, executing breeding tasks at a high level can help farms reach optimal reproductive success during the summer months.
Recommendations include:
- Minimize temperature changes to semen during handling and use.
- Expose weaned sows to boars beginning at day 1 post weaning
- Diligently check for signs of estrus (vulva swelling, discharge, vocalization, etc.) in addition to standing response, as estrus period can be shorter and less intense during warmer months.
- Use teams of boars during estrus detection, rotating boars out if use exceeds 1 hour.
- Utilize high libido, active boars.
- For farms experiencing delayed WEI, commercially available gonadotropins (PG600) administered at weaning may reduce days to estrus.
- Identify and document returns (regular returns, irregular returns, negative pregnancy check, Not in Pig) to troubleshoot when pregnancies are lost.
Heat stress is something every breeding herd must inevitably deal with. It’s important to recognize that sows can start to experience heat stress at temperatures above 70°F, with consistent temperatures above 80°F negatively impacting performance and reproduction. During warmer months, it is paramount to monitor gilt and sow behavior and keep cooling systems operating properly to maintain a favorable working environment for people and pigs alike.
