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Testing mammary gland secretions to help predict when a mare will foal
  1. Kenji Korosue, DVM, PhD
  1. Hidaka Training and Research Center, Japan Racing Association, Urakawa-gun, Hokkaido 057-0171, Japan
  1. e-mail: kenji_korosue{at}

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IN general, horses have a higher economic value than other domestic animals. Assisted foaling is performed in order to avoid complications associated with unattended births. Most mares foal late at night or early in the morning; and those attending the birth may spend many sleepless nights in anticipation of a foaling. Therefore, a method that can predict an accurate date and time of foaling, or show that a preparturient mare is not ready to foal, would be useful.

Historically, the prediction of the timing of foaling has been based on physical signs such as the udder filling with milk or the teat ends becoming waxy. These signs are indicative of foaling, but there is considerable variation in these signals among mares, none of which are an entirely accurate means of predicting when a given mare will foal.

Major changes in the electrolyte composition of mammary gland secretions of mares occur during late pregnancy. Before foaling, concentrations of sodium and chloride ions in mammary secretions decrease and concentrations of calcium, potassium, protein and lactose increase (Peaker and others 1979, Ousey and others 1984). The measurement of these electrolyte changes, especially with regard to calcium concentration, has become a widely used method in the horse industry for predicting foaling (Cash and others 1985, Ousey and others 1989). Measurement of calcium concentration is currently the sole subjective indicator …

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