Sleep is not a prerequisite for the milk ejection reflex in the pig

Area of Science:

• Veterinary Medicine
• Animal Physiology
• Neuroscience

Background:

• The milk ejection reflex is crucial for successful lactation in mammals.
• Previous research in rats suggested sleep is a necessary component of this reflex.

Purpose of the Study:

• To investigate the physiological and behavioral state of lactating sows during the milk ejection reflex.
• To determine if sleep is required for milk ejection in pigs.

Main Methods:

• Simultaneous recording of electroencephalographic (EEG) and electromyographic (EMG) activities in sows.
• Monitoring of intramammary pressure variations during suckling.
• Behavioral observations of sows during suckling and milk ejection.

Main Results:

• Milk ejection was characterized by a rapid increase in intramammary pressure.
• Sows exhibited a consistent state of arousal from the start of suckling until milk ejection.
• Polygraphic recordings and behavioral data confirmed sows were awake and alert.

Conclusions:

• Sleep is not a prerequisite for the milk ejection reflex in lactating sows.
• The findings contrast with previous research in rats, highlighting species-specific differences in lactation physiology.
• Arousal appears to be the critical state for initiating milk ejection in pigs.