title: Accuracy of bovine pregnancy detection using transrectal ultrasonography at 28 to 35 days after insemination.
abstract: OBJECTIVE
  To estimate the accuracy of real-time ultrasonography to detect pregnancy in dairy cows at 28 to 35 days after insemination.
  
  
  METHODS
  Cows that did not return to oestrus between 18 and 24 days after a first insemination (n = 526) were examined by transrectal ultrasonography from 28 to 35 days after insemination. Pregnancy was confirmed by the observation of a foetus, but fluid in the uterine horn and the presence of embryonic membranes were also noted. When pregnancy was not confirmed by the observation of a foetus, a second examination 7 days later, confirmed these remaining cows as pregnant or not pregnant to the first insemination. Detection of pregnancy at this early examination was compared with manual transrectal pregnancy examination performed 10 to 13 weeks after insemination (13-week examination).
  
  
  RESULTS
  There were 44% of cows that were pregnant to the first service, 34% that had returned for a second service 18 to 24 days after the first insemination, and 20% of cows that were not pregnant, and had not returned normally for a second service (non-pregnant, non-return) within 24 days of their initial insemination. The presence of a foetus at 28 to 35 days after insemination was accurately predicted by a simplified method where uterine fluid accumulation and embryonic membranes were observed. Foetal loss between the early detection and the 13-week examination (9% of pregnancies) indicated that 28 to 35 days post insemination was too early to reliably detect pregnancy.
  
  
  CONCLUSIONS
  Early examination of pregnancy with transrectal ultrasonography is an accurate method to identify non-pregnant, non-return cows. The examination can be simplified by the observation of uterine fluid accumulation and embryonic membranes, as opposed to the more involved process of observing the foetus.
authors.affiliation: Department of Veterinary Science, University of Melbourne, Werribee, Victoria 3030.
authors.forename: D P
authors.initials: DP
authors.lastname: Nation
authors.forename: J
authors.initials: J
authors.lastname: Malmo
authors.forename: G M
authors.initials: GM
authors.lastname: Davis
authors.forename: K L
authors.initials: KL
authors.lastname: Macmillan
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary; D011237:Predictive Value of Tests; D011247:Pregnancy; D011258:Pregnancy Tests / Q000379:methods / Q000662:veterinary*; D011270:Pregnancy, Animal / Q000502:physiology*; D012007:Rectum; D016216:Ultrasonography, Prenatal / Q000379:methods / Q000662:veterinary*