| Autor: |
Carlos E.C. Consentini, Tiago O. Carneiro, Humberto Neri, Emiliana O.S. Batista, Lucas O. e Silva, Alexandre H. Souza, Roberto Sartori |
| Jazyk: |
angličtina |
| Rok vydání: |
2022 |
| Předmět: |
|
| Zdroj: |
JDS Communications, Vol 3, Iss 3, Pp 212-216 (2022) |
| Druh dokumentu: |
article |
| ISSN: |
2666-9102 |
| DOI: |
10.3168/jdsc.2022-0212 |
| Popis: |
The present study evaluated the addition of gonadotropin-releasing hormone (GnRH) concomitant or 2 d after the beginning of protocols initiated with estradiol benzoate (EB). A total of 459 multiparous and 371 primiparous lactating Holstein cows were enrolled in the study. Weekly cohorts of cows were randomly assigned to 1 of 3 experimental groups that differed in the strategy to initiate the timed AI (TAI protocol. On d 0, all cows received a 1.55-g progesterone (P4) implant. Additionally, cows in the EBd0 group received 2 mg of EB i.m.; cows in the EBd0-GnRHd0 group were treated simultaneously on d 0 with 2 mg of EB plus 100 µg of gonadorelin diacetate tetrahydrate (GnRH) i.m.; and cows in the EBd0-GnRHd2 group received 2 mg of EB on d 0 and 100 µg of GnRH 48 h later (d 2). The remaining treatments in the protocol were similar among groups and included 0.53 mg (i.m.) of cloprostenol sodium (PGF2α) on d 7, followed by a second PGF2α treatment on d 9 (at the time of P4 implant withdrawal) and 1 mg of estradiol cypionate i.m. Then, TAI was performed on d 11 (48 h after P4 removal) in all experimental groups. We detected an effect of treatment on pregnancy per AI (P/AI) on d 30, in which cows from the EBd0-GnRHd2 group demonstrated greater fertility than EBd0 cows, whereas cows in the EBd0-GnRHd0 group did not differ among EBd0 and EBd0-GnRHd0 (40.5 vs. 30.4 vs. 34.4%, respectively). In summary, GnRH treatment at the beginning of an estradiol and P4-based TAI protocol increased fertility only when GnRH was given on d 2. Moreover, a more pronounced positive effect of this strategy was observed in particular classes of cows: multiparous cows, cows with greater milk production, and those receiving the first service. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
|
