The Effect of Treatment with Oestradiol Benzoate on Oestrus Expression and Endometrial Oedema in Anovulatory and Cyclic Mares.
Authors: Silva Elisa S M, Newcombe John R, Cuervo-Arango Juan
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Oestradiol benzoate (OB) is routinely administered to anovulatory mares to stimulate oestrous behaviour for breeding purposes, yet dose-response relationships and individual variation had not been systematically characterised. Researchers treated 13 anovulatory mares with five different OB doses (1–4 mg) across repeated cycles, measuring endometrial oedema and behavioural oestrus, whilst additional experiments tested whether a 3 mg dose could differentiate mares with an active corpus luteum (CL). A dose-dependent effect emerged, with 2 mg OB sufficient to induce both endometrial oedema and oestrous behaviour within 48 hours in most mares, though individual mare variation significantly influenced response intensity and duration; critically, mares retaining an active CL showed no endometrial oedema following 3 mg treatment, suggesting this response could serve as an indicator of luteal activity. These findings offer farriers and veterinarians a more evidence-based framework for selecting appropriate OB doses in reproductive management, potentially improving semen collection efficiency and embryo transfer protocols whilst reducing unnecessary over-treatment in individual animals.
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Practical Takeaways
- •2 mg oestradiol benzoate is an effective minimum dose for inducing oestrus in anoestrous mares within 48 hours, potentially reducing higher doses and associated costs
- •Individual mare variation in response is substantial, so veterinarians should monitor each mare's response and adjust dosing accordingly rather than applying a standard protocol
- •Confirming absence of an active corpus luteum before treatment is important, as the presence of CL may prevent the expected endometrial response to oestradiol benzoate
Key Findings
- •2 mg oestradiol benzoate was sufficient to induce endometrial oedema and oestrous behaviour within 48 hours in most mares
- •Dose-response and individual mare effects significantly influenced intensity and persistence of endometrial oedema and oestrous behaviour (p < 0.05)
- •Mares with an active corpus luteum showed no endometrial oedema response following 3 mg oestradiol benzoate treatment
- •Five sequential treatments with varying OB doses demonstrated reproducible effects within individual mares across multiple cycles