Concurrent lactation and pregnancy: pregnant domestic horse mares do not increase mother-offspring conflict during intensive lactation.

This research investigates the interaction between pregnant domestic horse mares and their offspring, particularly during periods of intensive lactation. The study reveals surprising findings that pregnant mares experience decreased conflict with their nursing foals during the first two trimesters of pregnancy, contrary to expectations.

Study Background and Purpose

• The study focuses on lactation, a highly energy-consuming part of parental care in mammals. It can lead to parent-offspring conflict due to the offspring’s demand for milk and the mother’s energy requirements.
• Notably, in some species, females can become pregnant soon after giving birth, leading to potential conflict from managing concurrent pregnancy and lactation.
• In horses (equids), it is known that pregnant females wean their foals earlier than non-pregnant ones. This study aimed to understand whether this increased conflict may also occur during intensive lactation periods before weaning.

Methodology and Measures

• The researchers hypothesized that mother-offspring conflict would be elevated in pregnant mares due to their need to maintain a pregnancy while also nursing a foal.
• They identified indicators of such conflict by observing the suckling behavior characteristics of domestic horses.

Key Findings

• Contrary to the assumptions, the study found that pregnant mares during their first two trimesters did not elevate mother-offspring conflict. Instead, they provided longer suckling bouts and were no more likely to reject or terminate suckling than non-pregnant mares.
• This finding indicates that pregnant mares may manage dual responsibilities to a nursed foal and a fetus by enhancing nursing behavior during early pregnancy. This behaviour happens before the initially low requirements of the fetus increase.
• Pregnant mares seem to compensate their suckling foal with early weaning due to the ongoing pregnancy.

Implications of the Study

• This research suggests a more nuanced understanding of parent-offspring conflicts during concurrent lactation and pregnancy in equine species, challenging pre-existing assumptions.