02597naa a2200349 a 450000100080000000500110000800800410001902200140006002400520007410000210012624501370014726000090028452015470029365000210184065000150186165000140187665000180189065000240190865000140193265000220194665000230196865000180199165000180200965000150202770000230204270000190206570000230208470000200210770000180212770000220214577300800216721797332025-10-16       2025    bl uuuu     u00u1 u    #d  a0049-47477 ahttps://doi.org/10.1007/s11250-025-04681-42DOI1 aNOLETO, G. C. S.  aEffect of EC-GnRH34 timed AI protocol on ovulation synchrony and fertility in crossbred Girolando dairy cows.h[electronic resource]  c2025  aThe objective of the present study was to evaluate whether the inclusion of a gonadotropin-releasing hormone (GnRH) treatment at a novel time (34 h) after intravaginal progesterone device (IPD) removal improves ovulation synchrony and increases fertility in crossbred Girolando dairy cows (B. taurus×B. indicus). A total of 226 crossbred Girolando lactating cows (predominantly 5/8, ¾, and ½ Holstein blood share) were subjected to an estradiol-progesterone based timed artificial insemination (TAI) protocol. At the IPD removal, all cows were treated with 1mg i.m estradiol cypionate (EC), and then allocated into two groups to receive either 2.5mL of saline solution (EC-Control, n=111) or 10.5μg i.m. buserelin acetate (GnRH analogue) 34 h after IPD removal (EC-GnRH34, n=115). A subgroup of 30 cows was examined by ultrasonography at 12h intervals to determine the time of ovulation after IPD removal. All cows were subjected to TAI 48 h after IPD removal. Cows in the EC-GnRH34 group ovulated earlier (60.4±3·8 h, p=0.03) and more synchronously (100%; p=0.006) than EC-Control cows (69.8±4·0 h and 60%). Females submitted to the EC-GnRH34 protocol had 42.6% pregnancy per AI (P/AI) compared with 35.1% for the ones treated with EC only (EC-Control, p=0.24). In conclusion, the present study demonstrated that the ovulation synchrony is optimized with the use of GnRH 34h after IPD removal. Fertility to the TAI protocol, however, was not significantly improved in comparison with cows treated with a single ovulation inducer, EC.  aAnimal fertility  aDairy cows  aGirolando  aGonadotropins  aHormonal regulation  aOvulation  aControle Hormonal  aFertilidade Animal  aGado Leiteiro  aGonadotrofina  aOvulação1 aSILVA, S. A. de S.1 aBARBOSA, I. P.1 aSIQUEIRA, L. G. B.1 aGASPERIN, B. G.1 aROVANI, M. T.1 aPFEIFER, L. F. M.  tTropical Animal Health and Productiongv. 57, n. 8, article 436, Nov. 2025.