{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T21:36:49Z","timestamp":1790199409101,"version":"4.1.0"},"reference-count":38,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2024,3,19]],"date-time":"2024-03-19T00:00:00Z","timestamp":1710806400000},"content-version":"vor","delay-in-days":18,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Reprod Domestic Animals"],"published-print":{"date-parts":[[2024,3]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>This study evaluated the efficacy of the administration of different doses of equine chorionic gonadotropin (eCG; 0\u2009IU, 200\u2009IU, or 300\u2009IU) at the time of the progesterone device removal in 2\u2010year\u2010old Nelore (<jats:italic>Bos indicus<\/jats:italic>) heifers synchronized for fixed\u2010timed artificial insemination (FTAI). On day 0 (D0), a total of 398 heifers received 2\u2009mg of oestradiol benzoate <jats:italic>i<\/jats:italic>.<jats:italic>m<\/jats:italic>., 0.53\u2009mg of cloprostenol <jats:italic>i<\/jats:italic>.<jats:italic>m<\/jats:italic>., and an eight\u2010day previously used (second use) intravaginal device containing 1\u2009g of progesterone (P4). Eight days later (D8), simultaneous with the P4 device removal, 0.5\u2009mg of oestradiol cypionate <jats:italic>i<\/jats:italic>.<jats:italic>m<\/jats:italic>. and 0.53\u2009mg of cloprostenol <jats:italic>i<\/jats:italic>.<jats:italic>m<\/jats:italic>. were administered. At the same time, heifers were randomly assigned to receive one of the following treatments: G\u20100\u2009IU (<jats:italic>n<\/jats:italic>\u2009=\u2009141; no eCG treatment), G\u2010200\u2009IU (<jats:italic>n<\/jats:italic>\u2009=\u2009132; treated with 200\u2009IU of eCG), and G\u2010300\u2009IU (<jats:italic>n<\/jats:italic>\u2009=\u2009125; treated with 300\u2009IU of eCG). FTAI was performed 48\u2009h after the P4 device removal (D10). Ultrasonographic evaluations were performed at D0, D10, and D17. Heifers were scanned to measure the size of the largest follicle (LF), the presence, number, and size of the corpus luteum (CL), and the ovulation rate. Subsequently, at D40, the heifers underwent scanning to determine the pregnancy rate and identify any twin pregnancies. Additionally, at D70, scans were performed to assess pregnancy loss (PG). Data were analysed by orthogonal contrasts [C1 (eCG effect): control x (200\u2009IU\u2009+\u2009300\u2009IU) and C2 (eCG dose effect): 200\u2009IU\u2009\u00d7\u2009300\u2009IU]. On D0, CL presence was similar between the groups [G\u20100\u2009IU\u2009=\u200965.2% (92\/141), G\u2010200\u2009IU\u2009=\u200955.3% (73\/132), and G\u2010300\u2009IU\u2009=\u200963.2% (79\/125); <jats:italic>p<\/jats:italic>\u2009=\u2009.16]. No interactions between the presence of CL on D0 and eCG treatment were found for any of the variables (<jats:italic>p<\/jats:italic>\u2009&gt;\u2009.05). The diameter of the LF at FTAI (D10) was not influenced by eCG treatment (<jats:italic>p<\/jats:italic>\u2009=\u2009.22) or eCG dose (<jats:italic>p<\/jats:italic>\u2009=\u2009.18). However, treatment with eCG increased the diameter of the CL at D17 (G\u20100\u2009IU\u2009=\u200915.7\u2009\u00b1\u20090.3\u2009mm<jats:sup>b<\/jats:sup>, G\u2010200\u2009IU\u2009=\u200916.6\u2009\u00b1\u20090.2\u2009mm<jats:sup>a<\/jats:sup>, and G\u2010300\u2009IU\u2009=\u200916.6\u2009\u00b1\u20090.3\u2009mm<jats:sup>a<\/jats:sup>; <jats:italic>p<\/jats:italic>\u2009=\u2009.001), regardless of the dose used (<jats:italic>p<\/jats:italic>\u2009=\u2009.94). The ovulation rate was higher in heifers treated with eCG [G\u20100\u2009IU\u2009=\u200979.4%<jats:sup>b<\/jats:sup> (112\/141), G\u2010200\u2009IU\u2009=\u200990.2%<jats:sup>a<\/jats:sup> (119\/132), and G\u2010300\u2009IU\u2009=\u200993.6%<jats:sup>a<\/jats:sup> (117\/125); <jats:italic>p<\/jats:italic>\u2009=\u2009.002], but there was no effect of eCG dose (<jats:italic>p<\/jats:italic>\u2009=\u2009.36). Pregnancy per AI (P\/AI) on D40 [G\u20100\u2009IU\u2009=\u200932.6%<jats:sup>b<\/jats:sup> (46\/141), G\u2010200\u2009IU\u2009=\u200942.4%<jats:sup>a<\/jats:sup> (56\/132), and G\u2010300\u2009IU\u2009=\u200942.4%<jats:sup>a<\/jats:sup> (53\/125); P\u2009=\u20090.05] and D70 [G\u20100\u2009IU\u2009=\u200929.1%<jats:sup>b<\/jats:sup> (41\/141), G\u2010200\u2009IU\u2009=\u200940.9%<jats:sup>a<\/jats:sup> (54\/132), and G\u2010300\u2009IU\u2009=\u200940.8%<jats:sup>a<\/jats:sup> (51\/125); <jats:italic>p<\/jats:italic>\u2009=\u2009.02] were higher on heifers that received eCG; however, no dose effect was observed for P\/AI on D40 (<jats:italic>p<\/jats:italic>\u2009=\u2009.89) nor D70 (<jats:italic>p<\/jats:italic>\u2009=\u2009.98). Pregnancy loss between D40 and D70 tended to reduce (<jats:italic>p<\/jats:italic>\u2009=\u2009.07) in eCG\u2010treated heifers without dose effect (<jats:italic>p<\/jats:italic>\u2009=\u2009.91). Heifers with CL at D0 presented a greater follicle diameter (LF) on D10 (With CL\u2009=\u200911.2\u2009\u00b1\u20090.2\u2009mm and Without CL\u2009=\u200910.2\u2009\u00b1\u20090.2\u2009mm; <jats:italic>p<\/jats:italic>\u2009=\u2009.05), CL diameter on D17 (With CL\u2009=\u200915.8\u2009\u00b1\u20090.03\u2009mm and Without CL\u2009=\u200911.8\u2009\u00b1\u20090.6\u2009mm; <jats:italic>p<\/jats:italic>\u2009=\u2009.01), and ovulation rate [With CL\u2009=\u200995.5% (233\/244) and Without CL\u2009=\u200974.7% (115\/154); <jats:italic>p<\/jats:italic>\u2009=\u2009.01]. However, no difference in pregnancy rate at D40 (<jats:italic>p<\/jats:italic>\u2009=\u2009.52) and D70 (<jats:italic>p<\/jats:italic>\u2009=\u2009.84) was found. In conclusion, eCG treatment increases ovulation and pregnancy rates of heifers submitted to a FTAI protocol. Furthermore, eCG treatment increases the diameter of the CL after FTAI and reduces pregnancy losses. No dose effect was observed, suggesting Nelore (<jats:italic>Bos indicus<\/jats:italic>) heifers respond to 200\u2009IU of eCG treatment for FTAI.<\/jats:p>","DOI":"10.1111\/rda.14553","type":"journal-article","created":{"date-parts":[[2024,3,19]],"date-time":"2024-03-19T11:49:35Z","timestamp":1710848975000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["The effectiveness of low\u2010dose of <scp>eCG<\/scp> in timed <scp>AI<\/scp> Nelore (<i>Bos indicus<\/i>) heifers"],"prefix":"10.1111","volume":"59","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9585-5455","authenticated-orcid":false,"given":"A. R. Felisbino","family":"Neto","sequence":"first","affiliation":[{"name":"Department of Animal Reproduction FMVZ\u2010USP  S\u00e3o Paulo S\u00e3o Paulo Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9255-3926","authenticated-orcid":false,"given":"D. F. 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