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      The effects of previous ovarian status on ovulation rate and early embryo development in response to superovulatory FSH treatments in sheep

      , , , ,
      Theriogenology
      Elsevier BV

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          Abstract

          A total of 64 ewes was used to determine if the changes in superovulatory yields related to the ovarian status at the start of superovulatory treatment are due to differences in the population of gonadotrophin-responsive follicles, alterations in the processes of ovulation or transport of embryos from oviduct to uterus and/or developmental competence of the oocyte/embryo. Ovarian status at the start of a superovulatory FSH step-down treatment, administered coincidentally with a progestagen, was assessed by ultrasonography. On Day 4 after progestagen withdrawal, embryos were recovered from oviduct and their viability was determined by assessing development in vitro culture (IVC) until the hatched blastocyst stage. In all the ewes, the ovulation rate was related positively to the number of 2-3 mm follicles at first FSH injection (P<0.005). However, the total number of embryos and their viability were related to the more limited category of 3 mm follicles (P<0.05), whereas a higher degeneration rate was related to the number of 2mm follicles. The presence of a corpus luteum (CL) at the start of superovulatory treatment exerted a protective effect on embryonic viability, decreasing the degeneration of embryos. On the other hand, the presence of a dominant follicle at first FSH dose affected the mean size of the pool of follicles responding to the superovulation treatment, because ovulation arose from 3 to 5 mm follicles in absence of large follicles (P<0.05), but from 2 to 3 mm follicles when large follicles were present (P<0.005), indicating atresia in medium sized follicles in the presence of a large follicle.

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          Author and article information

          Journal
          Theriogenology
          Theriogenology
          Elsevier BV
          0093691X
          April 2005
          April 2005
          : 63
          : 7
          : 1973-1983
          Article
          10.1016/j.theriogenology.2004.09.055
          15823353
          88442c48-e925-4b4d-b38b-06da893d4bd9
          © 2005

          http://www.elsevier.com/tdm/userlicense/1.0/

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