Abstract
Fourteen true repeat breeders with entirely normal oestrous cyclicity more than 1 year after calving and 14 control donor cows were superovulated with PMSG (2000 i.u.) and flushed non-surgically 6–8 days after the superovulatory heat. The superovulatory response was identical for the 2 groups such as assessed by the number of corpora lutea (9.4 ± 1.8 C.L. per repeat breeder and 9.1 ± 1.5 per control cow), occurrence of ovarian overstimulation (polycysts), presence of a non-countable amount of corpora lutea, negative outcome of the flushings and the number of recovered embryos (5.8 ± 1.0 embryos per repeat breeder and 6.0 ± 1.8 embryos per control cow). The most pronounced difference between the 2 categories of animals was related to the fertilization rate of embryos. In the repeat breeder group only 2.4 embryos per cow or 41 % were fertilized, whereas the control animals attained a fertilization rate of 4.9 embryos or 82 %. Since most factors liable to interfere with the fertilization process were identical for both groups (age, breed, nutritional and management conditions, semen quality, dose, AI-technician e.g.), it is believed that intraovarian, follicular, or follicular-dynamic conditions were responsible for producing a high proportion of non-fertilizable oocytes.
Keywords: non-surgical embryo transplantation, repeat breeders
Sammendrag
Ikke-kirurgisk opsamling af embryoner fra omløberkøer.
Fjorten regulære omløbere, d.v.s. køer som viste regelmaessig brunst efter kælvning, som ikke havde vist kliniske tegn på endometritis, og som var insemineret forgæves mere end 7 gange, blev sammen med 14 kontrolkøer superovuleret med PMSG og skyllet ikkekirurgisk 6–8 dage efter den superovulerede brunst. Superovulationssvaret målt ud fra antallet af ovulationer (9,4 ± 1,8 C.L. for omløbere og 9,1 ± 1,5 for kontroldyrene), forekomst af polycystiske ovarier (3 for omløbere og 4 for kontrolkøer) og ovarier med et stort antal corpora lútea (4 i hver gruppe), samt ved antallet af identificerede embryoner (5,8 ± 1,0 embryon pr. omløber og 6,0 ± 1,8 embryon pr. kontrolko) var ikke forskelligt for de 2 kategorier af dyr. Derimod blev der observeret en meget betydelig forskel i befrugtningsprocenten af embryoner (41 % for omløbere og 82 % for kontrolkøer). De fleste af de faktorer, som kan påvirke den normale befrugtningsprocent, var identiske for de 2 grupper, og det er muligt, at dybtgående forstyrrelser i dyrenes endokrine og follikeldynamiske processer var medvirkende årsager til den lave fertilitetsprocent hos omløberne.
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Footnotes
This study was supported by a grant from the Danish Agricultural and Veterinary Research Council.
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