Exposure to stallion accelerates the onset of mares' cyclicity.

Wespi, Bettina; Sieme, H; Wedekind, C; Burger, Dominik (2014). Exposure to stallion accelerates the onset of mares' cyclicity. Theriogenology, 82(2), pp. 189-194. Butterworths 10.1016/j.theriogenology.2014.03.019

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Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses.

Item Type:

Journal Article (Original Article)


05 Veterinary Medicine > Research Foci > Veterinary Public Health / Herd Health Management
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > Equine Clinic
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV)

UniBE Contributor:

Wespi, Bettina and Burger, Dominik


600 Technology > 630 Agriculture








Andrea Gassmann-Suter

Date Deposited:

29 Dec 2014 15:27

Last Modified:

15 Oct 2015 08:54

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

Anestrus, Cyclicity, Estrous cycle, Horse, Ovulation





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