title: Effects of exogenous oxytocin on uterine blood flow in puerperal dairy cows: the impact of days after parturition and retained fetal membranes.
abstract: The objective of this study was to examine whether an oxytocin challenge test (OCT), evaluated by measuring the changes in uterine blood flow using transrectal colour Doppler ultrasonography, is a suitable non-invasive method to determine uterine contractility in puerperal dairy cows. The changes in uterine blood flow during uterine contractions induced by oxytocin were evaluated on days 2 and 5 postpartum (pp). Twelve clinically healthy Holstein cows were randomly assigned into two groups: (1) oxytocin group (n=7), 50 IU oxytocin injected IM and (2) control group (n=5), 5 mL saline injected IM. Blood flow volume (BFV) and pulsatility index (PI) in the uterine arteries were determined before and after injection for 120 min on days 2 and 5 pp. BFV declined and PI increased rapidly after oxytocin injection on day 2 (P<0.05), whereas oxytocin on day 5 pp did not cause changes in blood flow parameters. The result confirmed that uterine responsiveness to oxytocin decreases with time postpartum in healthy cows. The same OCT was applied in cows with retained fetal membranes (n=6) on day 2 pp, however uterine blood flow showed no change after oxytocin injection. The results showed that an OCT on day 2 pp may be a useful method for investigating the uterine contractile response to oxytocin (reflected as the decrease of uterine blood flow) and the potential pathophysiology of uterine involution in cows.
authors.affiliation: Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, 0808555 Obihiro, Japan.
authors.forename: Fumie
authors.initials: F
authors.lastname: Magata
authors.forename: Desiree
authors.initials: D
authors.lastname: Hartmann
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ishii
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Miura
authors.forename: Hiroto
authors.initials: H
authors.lastname: Takahashi
authors.forename: Motozumi
authors.initials: M
authors.lastname: Matsui
authors.forename: Katsuya
authors.initials: K
authors.lastname: Kida
authors.forename: Akio
authors.initials: A
authors.lastname: Miyamoto
authors.forename: Heinrich
authors.initials: H
authors.lastname: Bollwein
mesh_terms: D000818:Animals; D002417:Cattle; D005321:Extraembryonic Membranes / Q000502:physiology*; D005260:Female; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D049590:Postpartum Period / Q000187:drug effects / Q000502:physiology*; D011673:Pulsatile Flow; D011897:Random Allocation; D012007:Rectum / Q000000981:diagnostic imaging; D012039:Regional Blood Flow; D013997:Time Factors; D018615:Ultrasonography, Doppler, Color / Q000379:methods* / Q000662:veterinary; D055988:Uterine Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000098:blood supply
chemical_list: D010121:Oxytocin