Impact of Manipulation of Progesterone Concentrations during Follicular Development on Ovulatory Follicle Growth and Timed AI Pregnancy Rate in Beef Cows

Wednesday, July 23, 2014: 12:30 PM
2104A (Kansas City Convention Center)
Fernanda M Abreu , The Ohio State University, Columbus, OH
Marco A Coutinho da Silva , The Ohio State University, Columbus, OH
Leandro H Cruppe , The Ohio State University, Columbus, OH
Martin L Mussard , The Ohio State University, Columbus, OH
Bo R Harstine , The Ohio State University, Columbus, OH
G. Allen Bridges , University of Minnesota, Grand Rapids, MN
Thomas W Geary , USDA ARS Fort Keogh, Miles City, MT
Michael L Day , The Ohio State University, Columbus, OH
Abstract Text:

This experiment was conducted to investigate the role of decreased progesterone (P4) concentrations during follicular development on fertility in multiparous beef cows (n=228; Angus x Simmental) from three locations (n=92; n=63; n=73). Ovulation was pre-synchronized with the 5-d CO-Synch+CIDR program with the d of the final GnRH designated as d -6. On d 0, all ovarian follicles were ablated. Cows were stratified by age and days postpartum within location, and assigned to receive either a previously used CIDR and two-25 mg PGF doses 8 h apart (low-P4; L; n=115) or a new CIDR (high-P4; H; n=113) on d 0. On d 5, CIDR were removed, two-25 mg PGF doses administered and estrus detection tail paint applied. Tail paint scoring (TPS; 1 = paint completely removed; 2 = paint partially removed; 3 = paint largely undisturbed and no evidence of mounting), timed-AI (TAI) and administration of 100 µg GnRH were performed on d 8. Blood samples for P4 analysis were collected on d 5. Ultrasonography was conducted on d 0, 5 and 8 to assess ovarian structures, and d 35 for pregnancy diagnosis. Cows without a CL on d 0 were removed from all analyses. Across locations, P4 concentrations on d 5 were greater (P < 0.05) in the H (4.91 ± 0.13 ng/mL) than L (0.99 ± 0.06 ng/mL); a treatment by location interaction (P < 0.05), predominantly due to elevated P4 concentrations in one location, was detected. Follicle diameter on d 5 was greater (P < 0.05) in the L (8.9 ± 0.2 mm) than H (7.4 ± 0.1 mm) treatment, but did not differ between treatments (12.0 ± 0.1 mm) at TAI. Hence, follicle growth from d 5 to 8 was greater (P < 0.05) in the H (1.5 ± 0.1 mm/d) than in the L (1.3 ± 0.1 mm/d) treatment. Distribution of TPS differed (P < 0.05) between treatments with a majority of cows in the H treatment with TPS 3 (57%) and a majority in the L treatment with TPS 1 (54%). Cows with TPS 1 or 2 had a greater (P < 0.05) PR than cows with a TPS 3. However, PR did not differ between the H (67.3%) and L (67.8%) treatments. In conclusion, decreased P4 resulted in an increased percentage of cows in estrus before TAI, but did not impact timed AI pregnancy rate in beef cows.


Progesterone, Fertility, Cows