Suckling behaviour does not measure milk intake in horses, Equus caballus

Area of Science:

• Animal behavior
• Mammalian reproduction
• Parental investment

Background:

• Parental investment studies in mammals often use suckling behavior to estimate maternal energy transfer.
• The assumption that increased suckling directly correlates with higher milk intake is widely used but lacks robust evidence.
• Previous literature reviews indicate limited support for suckling behavior as a reliable index of milk or energy transfer.

Purpose of the Study:

• To investigate the accuracy of suckling behavior as an indicator of milk and energy transfer from mares to foals.
• To determine if common measures of suckling behavior can reliably predict milk intake in thoroughbred horses.
• To assess the validity of using suckling behavior in studies of differential maternal investment.

Main Methods:

• Utilized a radioactive isotope technique to label mare's milk and quantify milk transfer to foals.
• Measured various aspects of suckling behavior, including duration and frequency.
• Correlated suckling behavior metrics with actual milk and energy intake data.

Main Results:

• No significant linear relationship was found between typical suckling behavior measures and milk or energy intake.
• Neither mare nor foal characteristics, nor suckling-associated behaviors, improved the predictive accuracy of milk intake.
• Female foals exhibited longer suckling durations than males, yet milk transfer did not differ significantly between sexes.

Conclusions:

• Suckling behavior is an inadequate predictor of milk intake in domestic horses.
• Conclusions regarding differential maternal investment in mammals based solely on suckling behavior may be erroneous.
• The study highlights the need for more accurate methods to measure maternal investment in mammals.