Hormonal interrelationships in postpartum suckled dairy cows.

Area of Science:

• Reproductive endocrinology
• Veterinary science
• Animal physiology

Background:

• Postpartum hormonal changes are critical for reproductive cyclicity in cows.
• Luteinizing hormone (LH) and prostaglandin F2 alpha (PGF2 alpha) are key regulators of the estrous cycle.
• Understanding these dynamics is essential for optimizing cattle reproduction.

Purpose of the Study:

• To investigate the temporal changes in key reproductive hormones in postpartum cows.
• To examine the influence of calf suckling and weaning on these hormonal profiles.
• To explore correlations between different hormones during the postpartum period.

Main Methods:

• Blood samples were collected from three cross-bred cows from parturition up to 62 days postpartum.
• Plasma concentrations of 15-keto-13,14-dihydro-PGF2 alpha, LH, prolactin, cortisol, and progesterone were measured using radioimmunoassay.
• Detailed sampling included frequent collections around parturition and weaning, and 24-hour sampling via catheter.

Main Results:

• Prostaglandin F2 alpha metabolite peaked around parturition and decreased significantly by day 21 postpartum.
• Plasma LH concentrations increased postpartum, with a notable rise after calf weaning.
• Correlations were observed between LH, prolactin, cortisol, and PGF2 alpha metabolite, with negative correlations between LH and cortisol, and positive correlations between prolactin and cortisol.

Conclusions:

• Calf weaning significantly impacts LH secretion in postpartum cows.
• Hormonal profiles, including PGF2 alpha metabolite, LH, prolactin, and cortisol, exhibit distinct patterns in the postpartum period.
• Interactions between these hormones suggest complex regulatory mechanisms influencing postpartum reproduction.