Elevated plasma cortisol during induced and spontaneous hypocalcemia in ruminants

Area of Science:

• Veterinary Medicine
• Endocrinology
• Animal Physiology

Background:

• Hypocalcemia, a common metabolic disorder in dairy cows post-calving, poses significant health risks.
• Cortisol, a key stress hormone, has a complex relationship with mineral metabolism during the transition period.

Purpose of the Study:

• To investigate the relationship between blood plasma cortisol and calcium/phosphorus levels in dairy cows around calving.
• To explore cortisol's role in hypocalcemia and its potential impact on recovery.

Main Methods:

• Plasma cortisol, calcium, and phosphorus were measured in 12 dairy cows (third+ parity) from 3 days pre-calving to 2.5 days postpartum.
• Cows were categorized into paretic, nonparetic, and borderline hypocalcemic groups based on plasma calcium levels.
• Exogenous cortisol administration and induced hypocalcemia experiments were conducted in goats.

Main Results:

• Cortisol concentrations were elevated in paretic and borderline cows compared to nonparetic cows, reflecting calcium stress.
• Paretic cows exhibited lower phosphorus levels postpartum.
• Calcium and phosphorus showed negative correlations with cortisol levels within cows.
• In goats, cortisol was released in response to hypocalcemia and exogenous cortisol administration did not induce hypocalcemia but potentially aided recovery.

Conclusions:

• Cortisol levels in dairy cows are indicative of the degree of calcium stress experienced around calving.
• Findings suggest cortisol plays a role in the physiological response to hypocalcemia and may contribute to recovery in ruminants.