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Exogenous PGF(2)alpha enhanced GnRH-induced LH release in postpartum cows
R D Randel1, M A Lammoglia, A W Lewis
1Texas A&M University Agricultural Research and Extension Center, Overton, TX 75684, USA.
Theriogenology
|February 1, 1996
Summary
This study investigated how prostaglandin F2-alpha (PGF2α) and gonadotropin-releasing hormone (GnRH) affect luteinizing hormone (LH) in postpartum Brahman cows. Results show GnRH increased LH, and PGF2α enhanced this effect, with varied responses based on parity and PGF2α dosage.
Area of Science:
- Reproductive Endocrinology
- Veterinary Science
- Animal Reproduction
Background:
- Postpartum anestrus is a significant challenge in beef cattle production, impacting rebreeding efficiency.
- Luteinizing hormone (LH) surge is critical for ovulation and subsequent fertility.
- Understanding factors influencing LH release postpartum is crucial for reproductive management.
Purpose of the Study:
- To evaluate the impact of exogenous prostaglandin F2-alpha (PGF2α) on circulating LH concentrations in postpartum multiparous and primiparous Brahman cows.
- To assess the influence of PGF2α dosage and concurrent gonadotropin-releasing hormone (GnRH) administration on LH release.
- To determine the effects of parity on the response to PGF2α and GnRH treatments.
Main Methods:
- Randomly allotted postpartum Brahman cows (multiparous n=32, primiparous n=46) to varying doses of PGF2α (0-3 mg/100 kg BW) with or without GnRH on Day 30 postpartum.
- Weekly blood sampling from calving through treatment to monitor serum progesterone and confirm anestrus prior to treatment.
- Radioimmunoassay (RIA) for serum progesterone determination and analysis of serum LH concentrations over time.
Main Results:
- Serum LH concentrations were significantly affected by time, PGF2α dose, GnRH, parity, and their interactions.
- Multiparous cows exhibited higher mean serum LH, LH peak pulse height, and area under the LH release curve compared to primiparous cows when not treated with GnRH.
- Exogenous GnRH increased LH in all cows, an effect further enhanced by simultaneous PGF2α treatment; primiparous cows showed a greater response to both PGF2α and GnRH.
Conclusions:
- Exogenous GnRH effectively stimulates LH release in postpartum Brahman cows.
- Co-administration of PGF2α with GnRH enhances LH release, suggesting a synergistic effect on pituitary function.
- Parity influences the LH response to PGF2α and GnRH, with primiparous cows demonstrating a heightened sensitivity to these treatments.
