Exposure to stallion accelerates the onset of mares' cyclicity

Wespi, Bettina; Sieme, Harald; Wedekind, Claus; Burger, Dominik

doi:10.1016/j.theriogenology.2014.03.019

Cited by 13 publications

(6 citation statements)

References 39 publications

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“…Induced ovulation as in cats, rabbits, ferrets or camelids43 is not described for horses. However, exposure to stallion was recently found to affect the mares’ cyclicity44. Such potential fitness-enhancing effects may explain why stallions would try to mount dioestrous mares and ejaculate semen, even if of comparatively low quality.…”

Section: Discussionmentioning

confidence: 99%

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Quality of seminal fluids varies with type of stimulus at ejaculation

Jeannerat

Janett

Sieme

et al. 2017

Sci Rep

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The theory of ejaculate economics was mainly built around different sperm competition scenarios but also predicts that investments into ejaculates depend on female fecundity. Previous tests of this prediction focused on invertebrates and lower vertebrate, and on species with high female reproductive potential. It remains unclear whether the prediction also holds for polygynous mammals with low female reproductive potential (due to low litter size and long inter-birth intervals). We used horses (Equus caballus) to experimentally test whether semen characteristics are adjusted to the oestrous cycle of the mare a stallion is exposed to during few moments before ejaculation. We analysed 122 weekly semen samples collected from 16 stallions during exposure to either an oestrous or a dioestrous mare. Semen volume and the rate of motile sperm were higher when stallions were exposed to an oestrous than to a diestrous mare, while total sperm counts and sperm velocity remained unchanged. Sperm collected after exposure to an oestrous mare also showed reduced oxidative degeneration of cell membranes over a period of 48 hours. We conclude that stallions invest more into their seminal fluids when the chance of fertilization is elevated, and that this adjustment of ejaculate quality can happen very quickly.

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Section: Discussionmentioning

confidence: 99%

“…In horses, a typical oestrous cycle takes approximately 3 weeks during the reproductive season44. The typical oestrous signals can normally be observed during approximately 5–7 days during each cycle, i.e.…”

Section: Discussionmentioning

confidence: 99%

Quality of seminal fluids varies with type of stimulus at ejaculation

Jeannerat

Janett

Sieme

et al. 2017

Sci Rep

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“…Here again, further studies are needed to investigate to what extent the present results can apply to sheep, but also to other seasonal ruminants or any species in which seasonal reproduction is controlled by photoperiod. For example, this could be the case in horses, since exposure to stallions advances the onset of the breeding season of mares (Wespi et al, 2014). Experimental designs used in experiments 1 and 2 to assess the importance of sexually active male bucks on the maintenance of out-of-season ovulatory activity in female goats.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Sexually active males prevent the display of seasonal anestrus in female goats

Delgadillo

Flores

Poindron

et al. 2015

Hormones and Behavior

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“…So far, photoperiod has received most attention as a cue for phenological adjustment of breeding, although other external stimuli, either social (presence of stallion, Wespi et al . ) or environmental such as green grass, may also play a role. Grass greenness should be a key parameter, especially for those species for which grasses are of central importance in favoring adequate breeding conditions.…”

Section: Discussionmentioning

confidence: 99%

Grass greenness flush can influence breeding phenology and fertility in equatorial thoroughbred mares in the absence of photoperiod variation

Carranza¹,

Yoong

Vergara

et al. 2018

Animal Science Journal

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Reproductive phenology is an important trait subjected to natural selection. Current horses in America belong to the Palearctic original populations after being introduced by European colonizers. Photoperiod variation is the main environmental factor for the adjustment of reproductive timing in horses, but is absent in equatorial areas. Here we hypothesize that seasonality of green-grass availability may influence breeding phenology in equatorial regions. We used data of 929 services to mares from 2006 to 2011 in a thoroughbred equine exploitation in Ecuador that experienced strong grass seasonality. Actual births could not be used to infer natural phenology because they were influenced by management decisions. Instead, we used variations in the probability of pregnancy after a service as a measure of the natural tendency of mares to show breeding phenology. We found that although managers tended to schedule pregnancies in two periods within the year, mares were more prone to become pregnant after the increase in grass greenness that takes place at the beginning of the year (February). Our finding has potential applications to improve the success of services and the welfare of animals, by providing green-grass stimuli in the appropriate season.

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Exposure to stallion accelerates the onset of mares' cyclicity

Cited by 13 publications

References 39 publications

Quality of seminal fluids varies with type of stimulus at ejaculation

Quality of seminal fluids varies with type of stimulus at ejaculation

Sexually active males prevent the display of seasonal anestrus in female goats

Grass greenness flush can influence breeding phenology and fertility in equatorial thoroughbred mares in the absence of photoperiod variation

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