Maternal influence on pre- and postnatal growth of foals born after embryo transfer.

This research investigates the impact of surrogate mother’s body size on the growth and development of the foal born after an embryo transfer from a donor mother of smaller size, by comparing it with a naturally gestated control group.

Objective of the Study

The study aims at understanding how the maternal environment, specifically the size of a surrogate mare, affects a foal’s pre-and postnatal growth when embryos from a smaller mare are transferred.

Methodology

• The experiment involved comparison of 3 pairs of gender-matching foals from birth to maturity.
• In each pair, one Polish Pony embryo was transferred from a donor mare, weighing 387-400 kg, to a much larger recipient mare, with weight ranging from 561-780 kg.
• The other embryo of each pair underwent a normal gestation process and served as a control group.
• The researchers examined the transferred and control horses at ages 9 and 13, and took X-ray pictures of their front legs to measure the length of the bones.

Findings

• The results demonstrated that the growth and development processes of transferred foals born to heavier recipient mares could be split into three phases.
• In the first fetal stage, the body weight gain and growth of the transferred embryos were faster compared to the control group.
• The second phase covered the suckling period. Although the transferred foals gained weight faster than the control foals, their growth rate was slower than in the first phase.
• In the third phase, which took place after weaning, the body weight gain and growth rate of the transferred foals were similar to the control foals.

The central conclusion of this study is that although the body size of surrogate mares affects the pre- and postnatal growth of transferred foals initially, this difference in growth rate evens out in the later stages of development, making them comparable to naturally gestated foals.