Concentrations of Progesterone during Early Follicular Development and Pregnancy Rate to AI in Beef Cows

Tuesday, July 22, 2014
Exhibit Hall AB (Kansas City Convention Center)
Fernanda M Abreu , The Ohio State University, Columbus, OH
Michael L Day , The Ohio State University, Columbus, OH
Marco A Coutinho da Silva , The Ohio State University, Columbus, OH
Crystal A Madsen , USDA ARS Fort Keogh, Miles City, MT
Thiago Martins , USDA ARS Fort Keogh, Miles City, MT
Leandro H Cruppe , 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
Abstract Text:

The objective was to investigate if decreased progesterone (P4) concentrations earlier during follicular growth would impact fertility in beef cows. Crossbred (Angus x Hereford) cows (n = 261) received estradiol benzoate (EB; 1 mg, i.m.) and a previously used CIDR  on d -7, to induce emergence of a new follicular wave approximately 3 days later (d -4). On d 0, all cows received 100 µg GnRH and were randomly assigned to one of the two treatments. In the high P4 (H; n = 131) treatment, the previously inserted CIDR was replaced with a new CIDR on d 0. In the low P4 (L; n = 130) treatment, 25 mg PGF was administered on d 0, and the CIDR previously inserted on d -7 remained. On d 5, blood samples to determine P4 concentrations were collected, all cows received two 25 mg PGF doses and CIDRs were removed. Estrous detection coupled with artificial insemination (AI) 12 h later (Estrus-AI) was performed for 60 h after PGF. Cows not detected in estrus within this period were bred by timed-AI (TAI) and received 100µg GnRH at 72 h. Pregnancy diagnosis was performed approximately 40 d after AI. P4 concentrations at CIDR withdrawal (d 5) were greater (P < 0.01) in the H (2.81 ± 0.10 ng/ml) than in the L (1.73 ± 0.05 ng/ml) treatment. Within the first 60 h after PGF, estrus response (82% vs. 85%) and estrus distribution (56.1 ± 0.7 h vs. 54.0 ± 0.7 h) did not differ between H and L treatments, respectively. Synchronized pregnancy rate was similar between H (77.1%) and L (82.3%) treatments. Across treatments, pregnancy rates were greater (P < 0.01) with Estrus-AI (82.9%) than TAI (63.6%). Concentrations of P4 on d 5 were negatively related (P< 0.01) with estrus response and time to estrus; across treatments. In conclusion, P4 concentrations during early follicular development did not influence synchronized pregnancy rate in beef cows.

Keywords: Beef cattle, Progesterone, Pregnancy rate