Human chorionic gonadotropin (hCG)-induced ovulation occurs later but with equal occurrence in lactating dairy cows: comparing hCG and gonadotropin-releasing hormone protocols
| Autor: | Tsung-Ching LIU, Chia-Tang HO, Kuang-Po LI, Chao-Chin CHANG, Jacky Peng-Wen CHAN |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | The Journal of Reproduction and Development, Vol 65, Iss 6, Pp 507-514 (2019) |
| Druh dokumentu: | article |
| ISSN: | 0916-8818 1348-4400 |
| DOI: | 10.1262/jrd.2019-037 |
| Popis: | This study assessed the effects of two hormones, human chorionic gonadotropin (hCG) and gonadotropin-releasing hormone (GnRH), on ovulatory responses during different diestrous stages in lactating dairy cows. Estrous cycles of 21 cows were synchronized and were enrolled in stage 1 of the experiment. The cows were treated with a prostaglandin (PG) F2α analog either 9 to 10 days [mid-diestrus (MD) group] or 5.5 to 6.5 days [early-diestrus (ED) group] after synchronized ovulation (day 0 = first PGF2α administration). On day 2, the cows were administrated 250 μg GnRH or 3000 IU hCG. Ovulation was determined every 2 h from 24 to 36 h after GnRH or hCG administration, and then every 4 h up to 72 h until ovulation. Cows in stage 2 were administered these treatments in the reverse order. The results indicated that average ovulation times in cows treated with GnRH in the MD group (GnRH-MD group) and cows treated with GnRH in the ED group (GnRH-ED group) were 30.0 ± 1.0 h and 28.8 ± 0.4 h, respectively. However, ovulation times for cows treated with hCG in the MD group (hCG-MD group) and cows treated with hCG in the ED group (hCG-ED group) were 35.8 ± 4.6 h and 32.8 ± 2.2 h, respectively, and ovulation occurred significantly later in the hCG-treated groups than in the GnRH-treated groups. In summary, we found that hCG-induced ovulation occurred later than GnRH-induced ovulation regardless of different diestrous peroids; however, the two treatments did not differ in terms of percentage of ovulation. |
| Databáze: | Directory of Open Access Journals |
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