Journal of Reproduction and Development
Online ISSN : 1348-4400
Print ISSN : 0916-8818
ISSN-L : 0916-8818
Validation of a novel timed artificial insemination protocol in beef cows with a functional corpus luteum detected by ultrasonography
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JOURNALS FREE ACCESS Advance online publication

Article ID: 2017-135


This study aimed to clarify the feasibility of a novel timed artificial insemination (TAI) protocol using ultrasonography, and to determine the associations between the ovarian component and fertility. In Experiment 1,272 Japanese Black cows with a corpus luteum (CL) ≥ 18 mm in diameter were divided randomly into either the TRT group (134 cows that were administered gonadotropin-releasing hormone [GnRH] 56 h [day 2] after prostaglandin F[PGF] administration [day 0], followed by TAI 16–20 h later) or the CN-1 group (138 cows that were administered PGF followed by AI after estrus detection). In addition, the CN-2 group was designated for 306 cows given PGF and inseminated after estrus detection in the past two years at the same farms. In Experiment 2, 38 cows had the same treatment as the TRT group, and the sizes of follicles and CL were video-recorded on days 0 and 2. In Experiment 1, the AI and ovulation synchronization rates were higher in the TRT group than those in the CN-1 group (100% vs. 87.0% and 89.2% vs. 33.3%, respectively) (P < 0.01). The pregnancy rate in the TRT group (60.4%) was higher than that in the CN-2 group (45.1%) (P < 0.05). In Experiment 2, cows with a larger CL diameter and greater CL volume on day 0 had a higher pregnancy outcome (P < 0.05). In conclusion, this protocol was effective for improving pregnancy rates in beef herds, and fertility was associated with the CL size at the time of PGF administration.

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