LH surge in Nelore cows (Bos indicus), after induced estrus or after ovarian superestimulation.
Considering that there is limited information about the preovulatory LH surge in Zebu cattle (Bos indicus), the purpose of the present work was to assess the LH surge in Nelore cows during the estrous cycle and after ovarian superestimulation of ovarian follicular development with FSH. This information is particularly important to improve superovulatory protocols associated with fixed-time artificial insemination. Nelore cows (n=12) had their estrus synchronized with an intravaginal device containing progesterone (CIDR-B) associated with estradiol benzoate administration (EB, 2.5 mg, i.m., Day 0). Eight days later all animals were treated with PGF2alpha (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38h after the first PGF2alpha injection, blood sampling and ovarian ultrasonography took place every 4h, during 37 consecutive hours. Frequent handling may have resulted in a stress-induced suppression of LH secretion resulting in only 3 of 12 cows having ovulations at 46.7+/-4.9 and 72.3+/-3.8 h, respectively, after removal of CIDR-B. Thirty days later, the same animals received the described hormonal treatment associated with FSH (Folltropin), total dose=200 mg) administered twice a day, during 4 consecutive days, starting on Day 5. Thirty-six hours after the first injection of PGF2alpha, to minimize stress, only seven blood samples were collected at 4h interval each, and ultrasonography was performed every 12 h until ovulation. In 11 of 12 cows (92%) the LH surge and ovulation were observed 34.6+/-1.6 and 59.5+/-1.9 h, respectively, after removal of progesterone source. The maximum values for LH in those animals were 19.0+/-2.6 ng/ml (mean+/-S.E.M.). It is concluded that, in Nelore cows submitted to a ovarian superstimulation protocol, the LH surge occurs approximately 35 h after removal of intravaginal device containing progesterone, and approximately 12h before the LH surge observed after an induced estrus without ovarian superstimulation.
Monteiro
Fabio Morato
FM
Department of Pharmacology, Institute of Bioscience, University of São Paulo State, Botucatu, São Paulo, Brazil. monteiro@iz.sp.gov.br
Melo
Danilas Salinet
DS
Ferreira
Marcelo Machado G
MM
Carvalho
Luciano Mundim
LM
Sartoreli e Sartoreli
Evandro
E
Ederhardt
Bruno G
BG
Nogueira
Guilherme de Paula
Gde P
Barros
Ciro Moraes
CM
D000818:Animals; D002417:Cattle / Q000097:blood*; D003008:Cloprostenol / Q000008:administration & dosage; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives; D004971:Estrus / Q000097:blood*; D004973:Estrus Synchronization / Q000097:blood*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D008186:Luteolytic Agents / Q000008:administration & dosage; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000502:physiology*; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D011374:Progesterone / Q000008:administration & dosage; D013480:Superovulation / Q000097:blood* / Q000187:drug effects; D014463:Ultrasonography
D008186:Luteolytic Agents; C074283:estradiol 3-benzoate; D003008:Cloprostenol; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone