03470naa a2200325 a 450000100080000000500110000800800410001902400350006010000210009524501970011626000090031352024820032265000280280465000180283265000280285065000170287865000120289565300140290765300130292165300150293470000170294970000200296670000180298670000200300470000220302470000180304670000170306470000170308177300460309821000262019-11-18       2019    bl uuuu     u00u1 u    #d7 a10.1017/S17517311190004542DOI1 aRODRIGUES, W. B.  aTimed artificial insemination plus heat IIbgonadorelin injection in cows with low estrus expression scores increased pregnancy in progesterone/estradiol-based protocol.h[electronic resource]  c2019  aThe use of tail chalk and estrus/heat expression scores (HEATSC) evaluation is instrumental in identifying cows with greater estrus expression and greater artificial insemination pregnancy rates (P/AI) in cows submitted to timed artificial insemination (TAI), and cows with low or no estrus expression present lower P/AI. It was intended in this study to improve the pregnancy rates in TAI for Bos indicus beef cows, and gonadotrophin-releasing hormone (GnRH) injection was hypothesized to increase pregnancy rates in a TAI program for cows submitted to progesterone?estradiol-based protocols with low or no estrus expression, evaluated by HEATSC. Cows (n= 2284) received a progesterone device and 2mg estradiol benzoate, after 8 days the device was removed and 1 mg estradiol cypionate, 150?g of D-cloprostenol and 300 IU equine chorionic gonadotropin was administered. All cows were marked with chalk and HEATSC evaluated (scales 1 to 3) at TAI performed on day 10. Animals with HEATSC1 and HEATSC2 ( n= 937) received 100?g de gonadorelin (GNRH group; n= 470), or 1ml saline (Control group; n= 467), and cows with HEATSC3 (named HEAT group; n= 1347) received no additional treatment. The larger dominant follicle, evaluated on day 8and at TAI (day 10), was greater in HEAT group ( P= 0.0145 and P &lt0.001, respectively). Corpus luteum (CL) area and progesterone concentration was evaluated on day 17, and CL area was larger in HEAT group, intermediary in Control and lower in GnRH group (Control= 2.68 cm2, GnRH= 2.37 cm2, HEAT group= 3.07 cm2, P &lt0.001). Greater progesterone concentrations were found in HEAT group than in Control and GnRH groups (Control= 4.74 ng/ml, GnRH= 4.29 ng/ml, HEAT group= 6.08 ng/ml, P&lt0.001). There was a difference in ovulation rate, greater in HEAT group than GnRH and Control groups (Control= 72.5%; GnRH= 81.25%; HEAT group= 90.71%; P= 0.0024). Artificial insemination pregnancy rates was greater in HEAT group (57.09% (769/1347) than in Control and GNRH groups, with positive effect of GnRH injection at the time of TAI in P/AI (Control= 36.18% (169/467), GnRH= 45.95% (216/470); P&lt0.0001). In conclusion, GnRH application in cows with low HEATSC (1 and 2) is a simple strategy, requiring no changes in TAI management to increase pregnancy rates in postpartum beef cows submitted to progesterone?estradiol-based TAI protocols, without reaching, however, the pregnancy rates of cows that demonstrate high estrus expression at the TAI.  aArtificial insemination  aCaiman yacare  aPaleosuchus palpebrosus  aReproduction  aJacaré  aFertility  aFollicle  aManagement1 aSILVA, A. S.1 aSILVA, J. C. B.1 aANACHE, N. A.1 aSILVA, K. C. da1 aCARDOSO, C. J. T.1 aGARCIA, W. R.1 aSUTOVSKY, P.1 aNOGUEIRA, E.  tAnimalgv. 13, n. 10, p. 2313-2318, 2019.