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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows

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Ferreira, R. M. ; Ayres, H. ; Gimenes, L. U. ; Torres, F. P. ; Lima, F. A. ; Veras, M. B. ; Guida, T. G. ; Sala, R. V. ; Baruselli, P. S.
Total Authors: 9
Document type: Journal article
Source: REPRODUCTION FERTILITY AND DEVELOPMENT; v. 29, n. 3, p. 468-475, 2017.
Web of Science Citations: 1

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n=481) received a progesterone device and 2mg oestradiol benzoate. After 8 days, the device was removed and 25mg dinoprost was administered. Cows were allocated to one of three (Study 1; n=57) or four (Study 2; n=424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P=0.28) and 60 days (35.9% vs 33.0%; P=0.61) after TAI. TAI 48 and 54h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P=0.63) and 60 days (33.8% vs 35.1%; P=0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI. (AU)

FAPESP's process: 12/07510-1 - Molecular evaluation of oocyte maturation and use of cytoplasmic transfer to increse oocyte competence of repeat breeder dairy cows
Grantee:Roberta Machado Ferreira Saran
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 09/00938-3 - Effect of season on oocyte quality and in vitro embryo production in Holstein cows (Bos taurus) of different categories
Grantee:Pietro Sampaio Baruselli
Support type: Regular Research Grants