title: Influence of deslorelin (GnRH-agonist) implant on plasma progesterone, first wave dominant follicle and pregnancy in dairy cattle.
abstract: The objectives of this study were to investigate the effect of a synthetic GnRH-agonist (Deslorelin) implant on CL function and follicle dynamics when administered 48 h after PGF2 alpha, in a timed-insemination protocol, and to determine if the incorporation of a Deslorelin implant into a timed-insemination protocol to synchronize ovulation would be beneficial to the establishment of pregnancy. In Experiment 1, 15 non lactating cyclic Holstein cows received Buserelin (8 micrograms, i.m.) on Day-9, Lutalyse (25 mg, i.m.) on Day-2, and then on Day 0 received either a Deslorelin implant (700 micrograms, s.c.; n = 5), Buserelin (8 micrograms, i.m.; n = 5), or no treatment (control; n = 5). Blood samples were collected on Days-9, -2, 0 and thereafter daily until the next ovulation. Ovaries were scanned by ultrasound on Days-9, -2, 0, 1 (day of ovulation) and 3 times a week thereafter until a subsequent ovulation. From Days 0 to 15, the rate of increase of plasma progesterone (P4) was greater (P < 0.01) for Deslorelin than for control and Buserelin. Establishment of the first-wave dominant follicle (FWDF) as a Class 3 (> 9 mm) follicle was delayed (P < 0.01) with Deslorelin (14.2 +/- 1.3 d) compared with the control (4.6 +/- 1.3 d) and Buserelin (5.0 +/- 1.5 d) treatments. The FWDF resumed growth after Day 13 in all 5 Deslorelin-treated cows, and 2 cows ovulated spontaneously. In 1 Deslorelin-treated cow, the FWDF regressed, and a second-wave dominant follicle ovulated, while 2 other Deslorelin cows failed to ovulate until after Day 36. The cumulative numbers of Class 2 and 3 follicles was lowest in the Deslorelin group (P < 0.01), while the cumulative number of Class 1 follicles was highest (Deslorelin > Buserelin > Control; P < 0.01). The number of days to CL-regression and days to subsequent estrus did not differ (P > 0.05) among treatments. In Experiment II, 16 lactating potentially subfertile (body condition score 2.25) cows received Cystorelin (100 micrograms, i.m.; Day-9), Lutalyse (25 mg, i.m.; Day-2), and either a Cystorelin injection (100 micrograms, i.m.; n = 8) or Deslorelin implant (700 micrograms, s.c.; n = 8) on Day 0 and inseminated 16 h later. Deslorelin-treated cows had a higher plasma P4 concentration between Days 0 and 16 (P < 0.05) than the 2 other groups, and 5 of the 8 cows in this group were pregnant (Day 45, palpation) compared with 1 of 8 cows in the Cystorelin group (P < 0.05). Incorporation of a Deslorelin implant into a timed-insemination protocol enhanced the pregnancy rate in cows of poor body condition. The results support the hypothesis that enhanced CL function and delayed establishment of the first-wave dominant follicle may enhance embryo survival.
authors.affiliation: Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Ambrose
authors.forename: M F
authors.initials: MF
authors.lastname: Pires
authors.forename: F
authors.initials: F
authors.lastname: Moreira
authors.forename: T
authors.initials: T
authors.lastname: Diaz
authors.forename: M
authors.initials: M
authors.lastname: Binelli
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
mesh_terms: D000818:Animals; D002064:Buserelin / Q000008:administration & dosage; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology; D004343:Drug Implants; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D003341:Luteolysis; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D010053:Ovary / Q000000981:diagnostic imaging / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D017329:Triptorelin Pamoate / Q000031:analogs & derivatives; D014463:Ultrasonography
chemical_list: D004343:Drug Implants; D005300:Fertility Agents, Female; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D002064:Buserelin; C066438:deslorelin