Reproductive performance of Thoroughbred mares on six commercial stud farms

Authors

  • I BRÜCK,

    1. University of Melbourne, Department of Veterinary Science, Princes Highway, Werribee, Victoria 3030
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    • *Royal Veterinary and Agricultural University, Department of Reproduction, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

  • GA ANDERSON,

    1. University of Melbourne, Department of Veterinary Science, Princes Highway, Werribee, Victoria 3030
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  • JH HYLAND

    Corresponding author
    1. University of Melbourne, Department of Veterinary Science, Princes Highway, Werribee, Victoria 3030
      †To whom reprint requests should be sent
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†To whom reprint requests should be sent

SUMMARY

The records of 1630 mare years from 6 Thoroughbred stud farms in south eastern Australia were analysed for the years 1981 to 1986. Overall pregnancy and foaling rates were 83.9% and 69.3%, respectively. When calculated per served oestrous cycle, pregnancy and foaling rates were 54.7% and 43.1%, respectively. Pregnancy and foaling rates were higher (P < 0.001) for mares 3 to 10 years of age than for older mares. There was no difference in the pregnancy rates of maiden, barren and foaling mares. The foaling rate was significantly higher (P < 0.001) in mares that became pregnant during the first served oestrous cycle (77.8%) than in mares that needed two served oestrous cycles to become pregnant (65.4%).

Of all diagnosed pregnancies, 19.5% were not completed. Pregnancy loss was lower (P < 0.05) in maiden (12.4%) than in barren (19.7%) or foaling (20.9%) mares.

Twins were diagnosed in 7.8% of all pregnancies. If one conceptus was lost without external interference, 84.1% of pregnancies went to term. If one conceptus was manually crushed, 55.9% of pregnancies were maintained. If prostaglandin was used to terminate twin pregnancies, 60% of mares so treated produced foals the following year.

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