Sows' responses to increased heat load - A review

Area of Science:

• Animal Science
• Environmental Physiology
• Swine Production

Background:

• Extensive research exists on air temperature effects on sows, but limited data addresses air humidity and velocity.
• Sows are susceptible to heat stress, impacting their well-being and productivity.

Purpose of the Study:

• To review and synthesize existing literature on the effects of air temperature on sow physiology, production, and behavior.
• To highlight the influence of air humidity and velocity, often overlooked factors in heat stress research.

Main Methods:

• Comprehensive literature review of studies exposing sows to varying air temperatures (15°C to 39°C).
• Analysis of data on physiological responses (rectal temperature, respiration rate) and production indicators (feed intake, milk yield).
• Inclusion of studies examining mitigation strategies like cooling methods.

Main Results:

• Rectal temperature increased by an average of 0.099°C per °C rise in air temperature above 25°C.
• Air temperature affects respiration rate, vaginal temperature, skin temperature, feed intake, milk yield, body weight loss, mortality, and behavior.
• Air humidity can have a significant impact, with a 40% relative humidity increase at 30°C being comparable to a 1.9°C temperature rise.

Conclusions:

• Air temperature is a critical environmental factor affecting sow performance and welfare.
• Air humidity's impact on sows is substantial and warrants further investigation, similar to its effects on finishing pigs.
• Understanding these thermal effects is crucial for developing effective heat stress mitigation strategies.