Role of progesterone concentrations during early follicular development in beef cattle: I. Characteristics of LH secretion and oocyte quality

• Published in: Animal reproduction science 2018-09, Vol.196, p.59-68
• Main Authors: Abreu, F.M., Coutinho da Silva, M.A., Cruppe, L.H., Mussard, M.L., Bridges, G.A., Harstine, B.R., Smith, G.W., Geary, T.W., Day, M.L.
• Format: Article
• Language: English
• Subjects: Animals; beef cows; Cattle; controlled internal drug release devices; corpus luteum; Corpus Luteum - cytology; Corpus Luteum - drug effects; Corpus Luteum - physiology; Estrus Synchronization; Female; follicular development; Luteinizing hormone; Luteinizing Hormone - drug effects; Luteinizing Hormone - secretion; messenger RNA; Oocyte competence; oocytes; Oocytes - cytology; Oocytes - drug effects; Oocytes - physiology; Ovarian Follicle - cytology; Ovarian Follicle - drug effects; Ovarian Follicle - physiology; Ovulation; Progesterone; Progesterone - pharmacology; Progestins - pharmacology; secretion; Used CIDR
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2018.06.020

Objective was to investigate the effect of different progesterone (P4) concentrations during early follicular development on luteinizing hormone (LH) secretion and oocyte characteristics in beef cows. Primiparous cows (n = 24) were estrous pre-synchronized and follicular ablation was performed (d 0) 6 days following the time of ovulation. At the time of follicular ablation, cows were assigned to either: 1) high P4 treatment - HiP4; a new CIDR was inserted on d 0 to supplement P4 from the existing corpus luteum [CL], or 2) low P4 treatment - LoP4; a previously-used CIDR and two doses of PGF 8 to 12 h apart were given on d 0. Concentrations of P4 were greater (P < 0.01) in the cows of the HiP4 than LoP4 group on d 1.5, 2.5, and 3.5. Peripheral concentrations of E2 were greater (P < 0.05) in the cows of the LoP4 than HiP4 group on d 2.5 and 3.5. Frequency of LH pulses was greater (P   0.10) between treatments. In conclusion, lower P4 concentrations during early follicular development resulted in increased LH pulse frequency and E2 concentrations, but did not affect characteristics of oocyte developmental competence.