title: Investigation of respiration of individual bovine embryos produced in vivo and in vitro and correlation with viability following transfer.
abstract: BACKGROUND
  Quantification of oxygen consumption by individual preimplantation embryos has the potential to improve embryo selection. This study investigated whether respiration rates of individual embryos are useful indicators of embryo viability. The effect of the Nanorespirometer on embryo viability was also evaluated.
  
  
  METHODS
  The respiration rates of individual day 7 bovine in vivo- (n=44) and in vitro-produced (n=156) embryos were measured using the Nanorespirometer. In vivo-produced embryos were individually transferred to recipients.
  
  
  RESULTS
  The respiration rates of in vivo-produced embryos increased with increasing morphological quality and stage of development (P < 0.05). Pregnancy rates on days 35 and 60 were 65 and 60%, respectively. The mean respiration rate did not differ significantly between embryos producing and not producing a pregnancy, but the transfer of embryos with respiration rates <0.78 nl/h, between 0.78 and 1.10 nl/h, and >1.10 nl/h resulted in 48, 100 and 25% pregnancy rate, respectively. The mean respiration rate of in vitro-produced embryos was higher than that of in vivo-produced embryos because of differences in the morphological quality and stage of development.
  
  
  CONCLUSIONS
  The Nanorespirometer does not adversely influence embryo viability, but the sample size was too small to confirm the significance of the correlation observed between respiration rates and viability.
authors.affiliation: Department of Genetics and Biotechnology, Danish Institute of Agricultural Sciences, Tjele, Denmark. ana.sousalopes@adelaide.edu.au
authors.forename: A S
authors.initials: AS
authors.lastname: Lopes
authors.forename: S E
authors.initials: SE
authors.lastname: Madsen
authors.forename: N B
authors.initials: NB
authors.lastname: Ramsing
authors.forename: P
authors.initials: P
authors.lastname: Løvendahl
authors.forename: T
authors.initials: T
authors.lastname: Greve
authors.forename: H
authors.initials: H
authors.lastname: Callesen
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D002417:Cattle; D046149:Embryo Culture Techniques / Q000662:veterinary; D004624:Embryo Transfer / Q000662:veterinary; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D010101:Oxygen Consumption; D011247:Pregnancy