Fetometry in Arabian horses.

Area of Science:

• Veterinary Medicine
• Reproductive Biology
• Equine Science

Background:

• Accurate monitoring of intrauterine fetal growth and gestational age is crucial for equine breeding management.
• Establishing reliable predictive equations and determining optimal windows for fetal sexing are essential for Arabian horse reproduction.

Purpose of the Study:

• To monitor intrauterine fetal growth in Arabian horses using ultrasonography.
• To establish predictive equations for gestational age estimation.
• To determine the optimal period for fetal sexing in Arabian horses.

Main Methods:

• Transrectal ultrasonography was used to monitor seven Arabian mares from insemination to parturition.
• Key embryonic and fetal parameters were measured, including embryonic vesicle (EV), crown-rump length (CRL), and various diameters (biparietal, stomach, chest, abdominal).
• Developmental milestones like EV detection, embryo proper visualization, organization, and ossification were recorded.

Main Results:

• Embryonic vesicle, embryo proper, organization, and ossification were visualized at specific gestational days (10.3±0.5, 21.3±1.3, 33.6±2.0, 57.7±3.5, respectively).
• Most biometric parameters showed strong linear correlations with gestational age (P < 0.0001), excluding CRL, ELL, and KDL.
• Fetal sexing was feasible from day 56 to 161, with peak accuracy (98%) and applicability (64.9%) between days 105 and 133.

Conclusions:

• Ultrasonographic monitoring offers reliable parameters for assessing fetal growth and estimating gestational age in Arabian horses.
• The period between 105 and 133 days of gestation is optimal for accurate fetal sex determination.
• These findings improve reproductive monitoring and breeding management in Arabian horse populations.