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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #328606
Title: Role of progesterone concentrations during early follicular development in beef cattle: II. Ovulatory follicle growth and pregnancy rates

Author
item ABREU, F - The Ohio State University
item Geary, Thomas
item COUTINHO DA SILVA, M - The Ohio State University
item CRUPPE, L - The Ohio State University
item MUSSARD, M - The Ohio State University
item Madsen, Crystal
item MARTINS, T - University Of Minnesota
item BRIDGES, G - University Of Minnesota
item HARSTINE, B - The Ohio State University
item DAY, M - The Ohio State University

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 6/22/2018
Publication URL: http://handle.nal.usda.gov/10113/6196652
Citation: Abreu, F.M., Geary, T.W., Coutinho Da Silva, M.A., Cruppe, L.H., Mussard, M.L., Madsen, C.A., Martins, T., Bridges, G.A., Harstine, B.R., Day, M.L. 2018. Role of progesterone concentrations during early follicular development in beef cattle: II. Ovulatory follicle growth and pregnancy rates. Animal Reproduction Science. 196:69-76. https://doi.org/10.1016/j.anireprosci.2018.06.011.
DOI: https://doi.org/10.1016/j.anireprosci.2018.06.011

Interpretive Summary: The objective of this study was to determine effects of progesterone during follicle growth on pregnancy in beef cows. Two similar experiments were conducted. Cows received either a high or low progesterone treatment during follicle growth. High and low progesterone treatments were confirmed by hormone assays of cow blood. Cows that received low progesterone treatment had high estrogen levels. Cows that received high progesterone treatment had low estrogen levels. High progesterone treated cows had smaller follicles at the end of treatment. However, these follicles grew more rapidly in the 3 days after treatment. Pregnancy rates were not different between low and high progesterone treated cows. Thus, high progesterone levels during follicle growth had no effect on pregnancy in cows.

Technical Abstract: Two experiments were conducted to investigate the role of decreased progesterone (P4) concentrations during early follicular development on ovulatory follicle growth and pregnancy rate in beef cattle. In Experiment 1, ovulation was synchronized with the 5 d CO-Synch + CIDR program in multiparous cows (n = 241). Six days after the 2nd GnRH injection of the pre-synchronization program (d 0), ablation of all visible follicles in the ovaries was performed and cows were assigned to receive either a previously used CIDR and 2x-25 mg PGF doses 8 h apart (LoP4), or a new CIDR (HiP4). On d 5, CIDR were removed from all cows, 2x-25 mg PGF were administered, and estrus detection tail paint was applied. Timed artificial insemination (TAI) was performed coupled with GnRH-induced ovulation on d 8. On d 5, P4 concentrations were greater (P < 0.01) in the HiP4 (4.91 ± 0.13 ng/mL) than LoP4 (0.99 ± 0.06 ng/mL) treatment. Conversely, d 5 E2 concentrations and follicular diameter were greater (P < 0.01) in the LoP4 (5.00 ± 0.23 pg/mL and 8.9 ± 0.20 mm) than HiP4 (1.54 ± 0.12 pg/mL and 7.38 ± 0.15 mm) treatment. Follicular diameter at TAI (12.0 ± 0.12 mm) and TAI pregnancy rate did not differ (P > 0.10)between treatments. In Experiment 2, a new follicular wave was induced with estradiol benzoate on d -7, and cows (n = 275) were assigned on d 0 to receive either 25 mg PGF and maintain the previously used CIDR (pre-synchronization; LoP4) or to replace the previously used CIDR with a new CIDR (HiP4). Moreover, all cows received GnRH on d 0. CIDR were removed from all cows on d 5 concomitant with 2x-25 mg PGF doses. Estrous detection coupled with AI 12 h later (Estrus-AI) was performed for 60 h after CIDR removal (d 5) with TAI coupled with GnRH administration at 72 h if estrus was not exhibited. P4 concentrations on d 5 were greater (P < 0.01) in the HiP4 (2.81 ± 0.10 ng/ml) than LoP4 (1.73 ± 0.05 ng/ml) treatment. Within cows that were detected in estrous after PGF administration, estrus response (83.5%) and interval to estrus (55.0 ± 0.5 h) did not differ between treatments. Synchronized pregnancy rate (Estrus-AI + TAI) was similar between treatments (79.7%). In conclusion, differences in P4 concentrations during early follicular development do not impact synchronized pregnancy rate in beef cows when afforded adequate and similar intervals of proestrus.