03502naa a2200289 a 450000100080000000500110000800800410001902200140006002400390007410000180011324501640013126000090029550007110030452018700101565300280288565300090291365300320292265300180295465300170297270000150298970000160300470000170302070000160303770000190305370000170307277301230308910128262020-02-05       2003    bl uuuu     u00u1 u    #d  a0093-691X7 a10.1016/S0093-691X(02)01230-X2DOI1 aCAVESTANY, D.  aUse of medroxyprogesterone acetate (MAP) in lactating Holstein cows within an Ovsynch protocolbfollicular growth and hormonal patterns.h[electronic resource]  c2003  aArticle history: Received 21 February 2002 / Accepted 27 August 2002 / Available online 19 November 2002. Funding information: The present study was partially financed by a grant (URU/5/023) from the International Atomic Energy Agency (IAEA). The authors are grateful to Dr. J.F. Roser for the donation of the bovine monoclonal antibody and to the NIDDK?s National Hormone Peptide Program and Dr. A.F. Parlow for the donation of the ovine LH used as standard in the LH assay, to Dra. Stella Lanzzeri for the conditioning of the milk samples for P4 RIA and to Mr. Ignacio Torres for helping in the handling of animals during the fieldwork. Corresponding author: Daniel Cavestany - email:cavestan@inia.org.uy  aABSTRACT. To evaluate the effects of incorporating medroxyprogesterone acetate (MAP) in an Ovsynch protocol, cyclic lactating dairy cows were assigned randomly to two groups (control and MAP, n = 8 each). Ovsynch treatment (Day 0: GnRH, Day 7: PG, Day 9: GnRH) was initiated at random stages of the estrous cycle (control) and an intravaginal polyurethane sponge impregnated with 300 mg of MAP was inserted intravaginally in the MAP group at Day 0 and removed at Day 7 of the Ovsynch protocol (MAP treatment). Ovaries were scanned daily from Day 0 until the second GnRH treatment on Day 9 and from then every 6 h for 36 h. Milk samples were collected three times weekly starting 17 days before the initiation of treatment to determine the stage of the cycle at the beginning of the Ovsynch protocol. Blood samples were collected to monitor estradiol (E2), progesterone (P4), LH, and 15-ketodihydro-PGF2α (PGFM) by RIA. Response to the first GnRH treatment varied with the stage of the cycle at the time of initiation of treatment, as cows in metestrous and late diestrous did not ovulate. In cows ovulating, growth rate of the new follicle was not affected by the addition of MAP. No treatment differences were found in E2 concentrations which reached a maximum at Day 9, consistent with the maximum follicular size. At Day 7, cows with luteal concentrations of P4 had increased concentrations of PGFM, but cows with basal P4 did not show an active release of prostaglandins. There were no treatment differences in the ovulatory response to the second GnRH-induced ovulation, with 11 of the 16 cows ovulating between 16 and 32 h. The addition of MAP to the Ovsynch protocol could not mimic the normal high progesterone levels needed to prevent premature ovulations in those cows with premature CL regression.  © 2002 Elsevier Science Inc. All rights reserved.  aEstrous synchronization  aGnRH  aMedroxyprogesterone acetate  aProstaglandin  aReproduction1 aMEIKLE, A.1 aKINDAHL, H.1 aVAN LIER, E.1 aMOREIRA, F.1 aTHATCHER, W.W.1 aFORSBERG, M.  tTheriogenology, 15 April 2003, Volume 59, Issue 8, Pages 1787-1798. Doi: https://doi.org/10.1016/S0093-691X(02)01230-X