Induction of maternal behavior in non-parturient adoptive mares.

The research paper focuses on inducing maternal behavior in non-parturient (non-pregnant, non-childbearing) Welsh pony mares using hormonal treatments and vaginal-cervical stimulation (VCS). The ultimate goal was to make them accept and care for a newborn foal that was not their biological offspring.

Hormonal and Stimulation Treatment

• The experiment intended to elicit maternal behavior by artificially inducing lactation in 16 nonparturient mares using a mix of hormones (estrogen, progesterone) and a dopamine antagonist (sulpiride). This dual approach was meant to mimic the physiological conditions experienced by mares during and after pregnancy.
• Each mare was confined behind a padded bar and a newborn foal was introduced to the adoptive mare’s vicinity, most notably near her head – a crucial step for the bonding process.
• From the 16 mares, 8 mares received two 3-minute periods of VCS at the time the foster foal was introduced. After the VCS, the foal was released and the researchers observed how it interacted with the mare until she accepted the foal to nurse without showing any signs of aggression.

Comparison between VCS-treated and Non VCS-treated Mares

• The study divided the adoption trials into two scenarios – one where the mares experienced VCS and one where they did not. The 8 mares who did not receive VCS were treated similarly to the first group, except for the VCS procedure.
• The paper finds that all 16 mares accepted and nursed their adopted foal eventually. However, the mares that had undergone VCS displayed significantly shorter acceptance latencies, accepting their foals faster compared to those who did not receive VCS.
• The duration of acceptance for mares in the VCS group did not differ significantly from biological mothers with their own offspring. This suggests that VCS played a significant role in facilitating a quicker bond between the mare and the foal.

Behavioral Observations Post-adoption

• In subsequent tests evaluating the preference of the mare, regardless of whether they underwent VCS or not, the mares displayed preference and attachment towards their ‘own’ adopted foal, akin to control mares with their biological offspring.
• Once the adoption process was successful, the maternal behavior exhibited by the non-parturient mares paralleled that of biological mothers. This indicates that the hormonal treatment combined with/without VCS was effective in invoking maternal instincts.
• The researchers speculate that the faster acceptance in the VCS group might be due to a release of oxytocin, a hormone known to facilitate bonding and social interaction, triggered by the VCS treatment.