02573naa a2200409 a 450000100080000000500110000800800410001910000200006024501460008026000090022650000110023552014460024665000160169265000170170865000160172565000170174165000190175865000170177765000110179465000140180565000170181965000190183665000170185565000270187265000230189965000090192265300130193165300200194465300090196465300120197365300270198565300200201265300220203270000160205470000180207077300750208813215841997-05-23       1997    bl uuuu     u00u1 u    #d1 aVALLE, E. R. do  aGonadotropin-releasing hormone enchances the calving rate of beef females administered Norgestomet and alfaprostol for estrus syncronization.  c1997  aCNPGC.  aOne hundred fify beef heifers and 403 beef cows suckling calves were adminstered norgestomet implants (8 d) and alfaprostol, a PGF analogue, approximately 28 h before implant removal. Thirty hours after implant removal, females were administered either GnRH via injection, GnRH via implantation, or no GnRH, The dosage of GnRH was 250 ug. and implants prolong the induced LH surge. Ovulation response, incidence of short cycles, and calving rate were analyzed as 2 x 2 x3 completely randomized factorial design with female (heifers and  cows), estrous cycles (with or without), and GnRH as the main effects. There were no interactions (P&gt.10), and becouse heifers and cows had responses that did not differ (P&gt.25), the were summarized togesther. Females with estrous cycles had a higher (P &lt.05) ovulation response, fewer (P &lt.01) calving rate than females without estrous cycles. Gonadotropin-releasing hormone treatment increasede the ovulation response (P v.01) and the calving rate (P &lt.05), and these responses were not affected (P &gt.10) by the method of GnRH administration. Based on these data, the increased ovolation response to GnRH may account for 29% of the increase in calving rate observed in the GnRH-treated females. In summary, in norgestomet and alfaprostol-synchronized females, GnRH enhanced calving rate regardless of how it was  administered. This increase was due to more than an increased ovulation rate.  abeef cattle  acalving rate  anorgestomet  aprogesterone  aprostaglandins  areproduction  asteers  aHormônio  aProgesterona  aProstaglandina  aReprodução  aSincronização do Cio  aTaxa de Natalidade  aVaca  aBeef cow  aBovino de corte  aGnRH  aNovilha  aOestrus syncronization  aPartuition rate  aSynthetic homones1 aCRUZ, L. C.1 aKESLER, D. J.  tJournal of Animal Science, Champaigngv.75, n.4, p.897-903, Apr. 1997.