Factors influencing equine chorionic gonadotrophin production in the mare.
Authors: Wilsher S, Allen W R
Journal: Equine veterinary journal
Summary
# Editorial Summary: Factors Influencing Equine Chorionic Gonadotrophin Production in the Mare Wilsher and Allen's longitudinal study across 61 pregnancies in Thoroughbred mares examined how maternal body condition, exercise and parity shape eCG hormone dynamics—parameters of genuine clinical significance given eCG's diagnostic value in pregnancy monitoring and its role in maintaining early luteal function. Three experimental arms investigated different variables: moderate versus excessive feeding regimens in maiden mares; daily exercise versus stall confinement during gestation; and eCG profiles across three successive pregnancies in the same individuals. The researchers measured eCG secretion comprehensively, quantifying area under the curve, peak serum concentrations, timing and rate of decline, before establishing reference ranges from the full cohort (peak 64.5 ± 3.7 iu/ml at day 62.4 post-ovulation, declining to undetectable by day 134.1). Critically, moderately fed mares produced significantly higher eCG than those in excessive condition, whilst exercised mares showed higher concentrations between days 60–90 of pregnancy; multiparous mares reached undetectable levels earlier than maiden animals. For practitioners managing fertility or interpreting pregnancy diagnostics, these findings suggest that body condition optimisation and appropriate exercise prescription warrant consideration as modulators of placental function, whilst parity-related changes in eCG kinetics may necessitate adjusted interpretation of hormone assays in older breeding stock.
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Practical Takeaways
- •Moderate body condition and nutrition during pregnancy supports optimal placental hormone production; excessive feeding suppresses eCG secretion which may affect early pregnancy establishment
- •Exercise during pregnancy reduces eCG concentrations in mid-gestation; consider adjusting workload if monitoring hormonal status in breeding mares
- •Older mares (third parity) show different eCG profiles; aging should be considered when interpreting pregnancy hormone levels and managing multiparous mares
Key Findings
- •Moderately fed mares produced significantly higher eCG levels (AUC and peak concentrations) compared to excessively fed mares during pregnancy
- •Non-exercised mares had significantly higher mean eCG concentrations between days 60-90 of gestation compared to exercised mares, though total AUC was similar
- •eCG became undetectable significantly earlier in third parity pregnancies compared to earlier parities
- •Mean eCG peak across 61 pregnancies was 64.5 iu/ml occurring at 62.4 days post-ovulation, becoming undetectable by 134.1 days with 50% decline occurring by day 85.0