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Quality of seminal fluids varies with type of stimulus at ejaculation.

  • Jeannerat E Swiss Institute of Equine Medicine ISME, Agroscope and University of Berne, Avenches, Switzerland.
  • Janett F Clinic of Reproductive Medicine, University of Zurich, Zurich, Switzerland.
  • Sieme H Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hanover, Hanover, Germany.
  • Wedekind C Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland.
  • Burger D Swiss Institute of Equine Medicine ISME, Agroscope and University of Berne, Avenches, Switzerland.
  • 2017-03-14
Published in:
  • Scientific reports. - 2017
Animals
Ejaculation
Estrus
Female
Horses
Male
Semen
Semen Analysis
Sexual Behavior, Animal
Sperm Count
Sperm Motility
English 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.
Language
  • English
Open access status
gold
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Persistent URL
https://sonar.ch/global/documents/247286
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