title: Relationship between colour flow Doppler sonographic assessment of corpus luteum activity and progesterone concentrations in mares after embryo transfer.
abstract: Colour-flow Doppler sonography has been described as a means of assessing corpus luteum (CL) function rapidly, because area of luteal blood vessels correlates well with circulating progesterone (P4) concentrations [P4] in oestrous cycling mares. The aim of this study was to assess the relationships between CL size and vascularity, and circulating [P4] during early pregnancy in mares, and to determine whether luteal blood flow was a useful aid for selecting an embryo transfer recipient. Equine embryos (n=48) were recovered 8 days after ovulation and were transferred to available recipient mares as part of a commercial program with the degree of synchrony in timing of recipient ovulation ranging from 1 day before to 4 days after the donor. Immediately prior to embryo transfer (ET), maximum CL cross-section and blood vessel areas were assessed sonographically, and jugular blood was collected to measure plasma [P4]. Sonographic measurements and jugular blood collection were repeated at day 4 after ET for all mares, and again at days 11, 18 and 25 after ET in mares that were pregnant. The number of grey-scale and colour pixels within the CL was subsequently quantified using ImageJ software. The CL blood flow correlated significantly but weakly with plasma [P4] on the day of transfer and on day 4 after ET in all mares, and on days 11 and 25 after ET in pregnant mares (r=0.30-0.36). The CL area and plasma [P4] were also correlated on each day until day 11 after ET (r=0.49-0.60). The CL colour pixel area decreased significantly after day 18, whereas CL area was already decreasing by day 4 after ET. The CL area, area of blood flow, or [P4] was predictive of pregnancy. Findings in the present study suggest that both CL area and blood flow are correlated with circulating [P4] at the time of transfer and in early pregnancy. Evaluation of the CL using B-mode or CF sonography, although practical, provides no improvement in the selection of recipients or prediction of pregnancy outcomes than methods employed currently.
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Yalelaan 114, 3584 CM, Utrecht University, Utrecht, the Netherlands. Electronic address: P.T.Brogan@uu.nl.
authors.forename: P T
authors.initials: PT
authors.lastname: Brogan
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Yalelaan 114, 3584 CM, Utrecht University, Utrecht, the Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Henning
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Yalelaan 114, 3584 CM, Utrecht University, Utrecht, the Netherlands; Department of Farm Animal Health, Faculty of Veterinary Medicine, Yalelaan 7, 3584 CM, Utrecht University, Utrecht, the Netherlands; Section of Reproduction, Faculty of Veterinary Science, University of Pretoria, Private Bag XO4, Onderstepoort 0110, South Africa.
authors.forename: T A E
authors.initials: TA
authors.lastname: Stout
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Yalelaan 114, 3584 CM, Utrecht University, Utrecht, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: de Ruijter-Villani
mesh_terms: D000818:Animals; D003338:Corpus Luteum / Q000098:blood supply / Q000166:cytology / Q000000981:diagnostic imaging*; D004624:Embryo Transfer / Q000662:veterinary; D004973:Estrus Synchronization / Q000502:physiology; D005260:Female; D006736:Horses / Q000097:blood / Q000502:physiology; D009929:Organ Size; D010060:Ovulation / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D012039:Regional Blood Flow; D018615:Ultrasonography, Doppler, Color
chemical_list: D011374:Progesterone
keywords: Colour flow Doppler; Embryo transfer; Equine; Mare; Progesterone