title: Effect of combined exogenous progesterone with luteotrophic support via equine chorionic gonadotrophin (eCG) on corpus luteum development, circulating progesterone concentrations and embryo development in cattle.
abstract: The aim was to examine the effect of a single intramuscular (i.m.) injection of equine chorionic gonadotrophin (eCG) on Day 3 after oestrus on corpus luteum (CL) development, circulating progesterone and conceptus development in cross-bred beef heifers. In Experiment 1, heifers received: (1) saline, or a single i.m. injection of eCG on Day 3 at (2) 250IU (3) 500IU (4) 750IU or (5) 1000IU. Administration of eCG resulted in increased luteal tissue area and progesterone and oestradiol concentrations compared with controls. In Experiment 2, heifers received (1) a progesterone-releasing intravaginal device (PRID Delta) from Day 3 to 5 or (2) a PRID Delta from Day 3 to 5 plus a single injection of 750IU eCG on Day 3. In vitro-produced blastocysts (n=10 per recipient) were transferred on Day 7 and heifers were slaughtered on Day 14 to assess conceptus development. Administration of eCG reduced the number of short cycles (6.3% vs 31.3%) and increased mean luteal tissue weight (P=0.02). Insertion of a PRID Delta on Day 3 resulted in an elevation (P<0.05) in serum progesterone until removal on Day 5. Administration of eCG at the time of PRID Delta insertion resulted in higher progesterone levels (P<0.05) from Day 10 onwards. Conceptus dimensions were not affected. In conclusion, a single injection of eCG on Day 3 increased CL size and progesterone concentrations and, when given in conjunction with a progesterone-releasing device, appeared to reduce the number of short cycles, presumably due to its luteotrophic nature. The implications of the elevated oestradiol concentrations for embryo quality require further study.
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: L
authors.initials: L
authors.lastname: O'Hara
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: N
authors.initials: N
authors.lastname: Forde
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Duffy
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: F
authors.initials: F
authors.lastname: Randi
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: A K
authors.initials: AK
authors.lastname: Kelly
authors.affiliation: CEVA Sante Animale, 10 Avenue de la Ballastiere, 33500 Libourne, France.
authors.forename: A
authors.initials: A
authors.lastname: Valenza
authors.affiliation: CEVA Sante Animale, 10 Avenue de la Ballastiere, 33500 Libourne, France.
authors.forename: P
authors.initials: P
authors.lastname: Rodriguez
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Lonergan
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000187:drug effects / Q000378:metabolism; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000008:administration & dosage*; D003338:Corpus Luteum / Q000187:drug effects* / Q000378:metabolism; D003340:Corpus Luteum Maintenance / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D010064:Embryo Implantation / Q000187:drug effects; D004624:Embryo Transfer / Q000662:veterinary; D004958:Estradiol / Q000097:blood; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage*; D005307:Fertilization in Vitro / Q000662:veterinary; D006064:Gonadotropins, Equine / Q000008:administration & dosage*; D007273:Injections, Intramuscular; D006080:Ovarian Follicle / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood; D027724:Reproductive Techniques, Assisted / Q000662:veterinary*; D013997:Time Factors
chemical_list: D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; D006064:Gonadotropins, Equine; D011374:Progesterone; D004958:Estradiol