Enhanced or reduced fetal growth induced by embryo transfer into smaller or larger breeds alters post-natal growth and metabolism in pre-weaning horses.
Authors: Peugnet Pauline, Wimel Laurence, Duchamp Guy, Sandersen Charlotte, Camous Sylvaine, Guillaume Daniel, Dahirel Michèle, Dubois Cédric, Jouneau Luc, Reigner Fabrice, Berthelot Valérie, Chaffaux Stéphane, Tarrade Anne, Serteyn Didier, Chavatte-Palmer Pascale
Journal: PloS one
Summary
# Editorial Summary Placental nutrient supply in horses is directly constrained by uterine size, a factor that has profound implications for both prenatal development and postnatal metabolic competence. Researchers used embryo transfer across three breed sizes—ponies, saddlebreds, and draft horses—to experimentally manipulate fetal growth, creating six experimental groups (enhanced growth via small embryos in large uteri; restricted growth via large embryos in small uteri; and matched controls) that were followed from birth through weaning with assessments of weight gain, thyroid hormones, and glucose metabolism. Enhanced fetal growth in pony embryos carried by draft mares produced foals that remained significantly heavier through weaning with suppressed T3 concentrations, early hyperinsulinaemia and lower fasting glucose from 30–200 days, though insulin sensitivity normalised by weaning; conversely, restricted fetal growth in saddlebred embryos in pony mares produced consistently lighter foals with elevated newborn T3, higher fasting glucose, and enhanced insulin sensitivity at day 200. The divergent metabolic adaptations—early insulin resistance in enlarged foals versus improved insulin sensitivity in growth-restricted foals—persisted until weaning despite normalised postnatal environments, suggesting that the intrauterine epigenetic imprint on glucose homeostasis operates independently of ongoing size matching and warrants consideration in breeding predictions and management strategies for at-risk foals.
Read the full abstract on PubMed
Practical Takeaways
- •Embryo transfer outcomes in foals show lasting metabolic differences based on fetal environment; monitor glucose metabolism and growth rates differently depending on recipient mare size relative to genetic origin
- •Foals from enhanced fetal growth (large recipient mare) may show early insulin resistance despite normal birth weight—consider metabolic monitoring and dietary management for metabolic health
- •Small recipient mares carrying larger-breed embryos produce metabolically compensated foals with enhanced insulin sensitivity by weaning, suggesting adaptive capacity that may influence long-term health outcomes
Key Findings
- •Enhanced fetal growth (P-D foals) resulted in consistently heavier foals until weaning with reduced T3 concentrations and early insulin resistance despite lower fasting glucose levels
- •Restricted fetal growth (S-P foals) produced lighter foals with elevated neonatal T3 and higher fasting glucose from days 30-200, but developed increased insulin sensitivity by weaning
- •Uterine size acts as a primary determinant of fetal nutrient supply and induces divergent post-natal metabolic adaptive responses that persist until weaning
- •IGF-1 concentrations were not affected by either enhanced or restricted fetal environments, suggesting thyroid hormones and insulin metabolism are the primary adaptive pathways