Placental structure and function in different breeds in horses.

Area of Science:

• Comparative placental biology in equids.
• Equine reproductive physiology and development.
• Veterinary sciences and animal models.

Background:

• Horse breeds exhibit variations in size and metabolism, impacting their use as experimental models.
• Limited data exists on breed-specific placental structure and function in horses.
• Understanding these differences is crucial for accurate research and breeding practices.

Purpose of the Study:

• To investigate placental size, structure, and function differences across pony, Saddlebred, and draft horse breeds.
• To correlate these placental traits with foal size and weight at birth.
• To analyze gene expression related to placental development and function in different breeds.

Main Methods:

• Comparative analysis of placental morphology and stereology in ponies, Saddlebreds, and draft horses.
• Measurement of foal and total fetal membranes (TFM) weight.
• Quantitative assessment of placental vascularization and gene expression using histological sections and molecular techniques.

Main Results:

• Foals and TFM were significantly lighter in ponies compared to Saddlebred and draft horses.
• Pony placentas exhibited increased microcotyledonary vessel density compared to Saddlebreds.
• Gene expression related to growth, development, and vascularization varied between breeds and correlated with maternal and foal weight.

Conclusions:

• Equine placental structure and function are breed-dependent, with notable differences between ponies and larger horse breeds.
• Maternal size is a key determinant of foal and placental weight, influencing placental gene expression.
• Primiparous dams and female foals showed specific associations with placental characteristics, highlighting factors influencing equine pregnancy outcomes.