title: Effects of ovarian structures identified at Ovsynch™ enrolment, disease history and lactation variables on odds of pregnancy to a fixed-time artificial insemination after Ovsynch™.
abstract: OBJECTIVE
  To determine the effects of ovarian structures present at Ovsynch™ enrolment, disease history, lactation variables and times bred on pregnancy per fixed-time artificial insemination (FTAI) following fixed-time insemination after Ovsynch and to determine the relationship between the size of ovarian follicular structures and concurrent presence of a corpus luteum (CL).
  
  
  METHODS
  The study was conducted in a 3000-cow Holstein dairy herd. Over a 6-month period, 886 non-pregnant cows were examined by transrectal ultrasound and enrolled into 1132 Ovsynch events. Enrolled cows were synchronised using an Ovsynch-56 protocol. At enrolment, both ovaries were scanned by transrectal ultrasound to identify and record the presence and size of ovarian structures. Cows that did not return to oestrus were pregnancy tested 32-38 days post-insemination. Univariable and multivariable generalised linear mixed models (GLMMs) were used to determine the effect of each variable on pregnancy per FTAI. A univariable GLMM was also used to analyse the relationship between size of the dominant follicular structure and concurrent presence of a CL.
  
  
  RESULTS
  CL size (P = 0.039) and presence of a luteal cyst (P = 0.002) at Ovsynch enrolment significantly increased the odds of pregnancy. Occurrence of lameness (P = 0.035) or mastitis (P = 0.008) between calving and enrolment significantly decreased the odds of pregnancy. Neither the presence nor size of a follicular structure significantly affected the odds of pregnancy, although cows with larger follicular structures were less likely to have a concurrent CL (P < 0.001).
  
  
  CONCLUSIONS
  Presence of luteal tissue at Ovsynch enrolment and recent disease events affected pregnancy per FTAI in cows inseminated after Ovsynch.
authors.affiliation: Livestock Veterinary Teaching and Research Unit, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, New South Wales 2570, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Ingenhoff
authors.affiliation: Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, NSW, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Hall
authors.affiliation: Livestock Veterinary Teaching and Research Unit, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, New South Wales 2570, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Ranjbar Ni
authors.affiliation: Livestock Veterinary Teaching and Research Unit, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, New South Wales 2570, Australia.
authors.forename: J K
authors.initials: JK
authors.lastname: House
mesh_terms: D000818:Animals; D002417:Cattle / Q000033:anatomy & histology / Q000502:physiology*; D003338:Corpus Luteum / Q000000981:diagnostic imaging*; D004973:Estrus Synchronization; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation / Q000502:physiology; D007794:Lameness, Animal / Q000150:complications / Q000503:physiopathology; D008414:Mastitis, Bovine / Q000150:complications / Q000503:physiopathology; D006080:Ovarian Follicle / Q000000981:diagnostic imaging*; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage; D014463:Ultrasonography
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone
keywords: Ovsynch™; conception rate; corpus luteum; dairy cattle; follicle; luteal cyst; reproduction