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 informa...

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Published in:	Animal reproduction science Vol. 110; no. 1; pp. 128 - 138
Main Authors:	Monteiro, Fabio Morato, Melo, Danilas Salinet, Ferreira, Marcelo Machado G, Carvalho, Luciano Mundim, Sartoreli, Evandro Sartoreli e, Ederhardt, Bruno G, Nogueira, Guilherme de Paula, Barros, Ciro Moraes
Format:	Journal Article
Language:	English
Published:	Netherlands Elsevier B.V 2009 [Amsterdam]: Elsevier Science
Subjects:	Animals artificial insemination Bos indicus Cattle - blood Cloprostenol - administration & dosage controlled internal drug release devices cows Estradiol - administration & dosage Estradiol - analogs & derivatives Estrous cycle estrus Estrus - blood Estrus Synchronization - blood Female follicle-stimulating hormone follicular development hormonal regulation hormone secretion luteinizing hormone Luteinizing Hormone - blood Luteolytic Agents - administration & dosage Nellore Ovarian Follicle - diagnostic imaging Ovarian Follicle - physiology ovarian follicles ovulation Ovulation Induction - methods Ovulation Induction - veterinary physiological regulation physiological response progesterone Progesterone - administration & dosage Superovulation Superovulation - blood Superovulation - drug effects temporal variation Ultrasonography zebu Zebu cattle Zebu cattle Bos indicus Estrous cycle LH Superovulation
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Summary:	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 PGF2α (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38 h after the first PGF2α injection, blood sampling and ovarian ultrasonography took place every 4 h, 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 PGF2α, to minimize stress, only seven blood samples were collected at 4 h 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 12 h before the LH surge observed after an induced estrus without ovarian superstimulation.
Bibliography:	http://dx.doi.org/10.1016/j.anireprosci.2008.01.003 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0378-4320 1873-2232
DOI:	10.1016/j.anireprosci.2008.01.003