title: Effect of hCG administration during corpus luteum establishment on subsequent corpus luteum development and circulating progesterone concentrations in beef heifers.
abstract: This study examined the effect of a single administration of human chorionic gonadotrophin (hCG) on Day 1 to 4 after oestrus on corpus luteum (CL) development and circulating progesterone (P4). Oestrus-synchronized heifers (n=43) were administered a single intramuscular injection of saline on Day 1 (control) or 3000IU hCG on Day 1, 2, 3 or 4 after oestrus. Administration of hCG on Day 1 had no effect on CL area, on Day 2 increased CL area from Day 6 to 12 (P<0.05), on Day 3 increased CL area from Day 9 to 11, while on Day 4 increased CL size on Days 9 and 10 (P<0.05). Administration of hCG on Day 4 induced the formation of an accessory CL in 89% of heifers, resulting in a significant increase in total luteal tissue area on the ovaries compared with all other groups. Consistent with the effects on the CL, hCG on Day 1 did not affect P4 concentrations, on Day 2 significantly increased P4 compared with the control from Day 6 to 11 (P<0.05), on Day 3 resulted in a non-significant increase in P4 while hCG on Day 4 increased P4 from Day 8 to 13 compared with the control (P<0.05). In conclusion, administration of hCG as early as Day 2 after oestrus results in increased P4 in circulation from Day 6, which should have beneficial downstream effects in terms of uterine receptivity and conceptus elongation.
authors: Departamento de Reproduccion Animal, Instituto Nacional de Investigacion y Tecnolog?a Agraria y Alimentaria (INIA), Carretera de la Coruna, KM 5.9, 28040 Madrid, Spain.
authors: V
authors: V
authors: Maillo
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: P
authors: P
authors: Duffy
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: L
authors: L
authors: O'Hara
authors: Departamento de Reproduccion Animal, Instituto Nacional de Investigacion y Tecnolog?a Agraria y Alimentaria (INIA), Carretera de la Coruna, KM 5.9, 28040 Madrid, Spain.
authors: C
authors: C
authors: de Frutos
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: A K
authors: AK
authors: Kelly
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: P
authors: P
authors: Lonergan
authors: Departamento de Reproduccion Animal, Instituto Nacional de Investigacion y Tecnolog?a Agraria y Alimentaria (INIA), Carretera de la Coruna, KM 5.9, 28040 Madrid, Spain.
authors: D
authors: D
authors: Rizos
mesh_terms: D000818:Animals; D001947:Breeding / Q000379:methods; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003338:Corpus Luteum / Q000000981:diagnostic imaging / Q000187:drug effects / Q000254:growth & development*; D004973:Estrus Synchronization; D005260:Female; D006801:Humans; D034461:Luteinization / Q000187:drug effects / Q000502:physiology*; D015233:Models, Statistical; D011374:Progesterone / Q000097:blood*; D014463:Ultrasonography
chemical_list: D006063:Chorionic Gonadotropin; D011374:Progesterone