Model Answer
0 min readIntroduction
Hypocalcemic tetany (HT), also known as milk fever, is a metabolic disorder affecting lactating dairy animals, particularly milch cattle, characterized by a sudden and severe drop in blood calcium levels. This condition frequently occurs shortly after or during parturition (calving) when calcium demand significantly increases to support milk production. The rapid decline in calcium can lead to neuromuscular dysfunction, causing muscle tremors, stiffness, and, in severe cases, death. HT poses a significant economic threat to dairy farmers due to reduced milk yield, increased veterinary expenses, and potential animal losses. Understanding the etiology and management of HT is vital for sustainable dairy farming practices.
Definition and Etiology
Hypocalcemic tetany arises from a disruption in calcium homeostasis. Normally, calcium is mobilized from bone to meet the demands of lactation. However, if calcium intake is insufficient or the mobilization process is impaired, serum calcium levels plummet. Factors contributing to this include inadequate dietary calcium, low vitamin D status (which aids calcium absorption), and genetic predisposition in certain breeds like Holstein Friesian. The normal serum calcium level in cattle is 2.1 to 2.5 mmol/L; HT is diagnosed when levels fall below 1.5 mmol/L.
Clinical Signs and Symptoms
The clinical signs of HT progress rapidly. Initially, animals may show restlessness, muscle twitching (fasciculations), and hypersensitivity to stimuli. As the condition worsens, muscle stiffness, incoordination, and eventually, recumbency (lying down) occur. Severe cases may exhibit convulsions and respiratory distress. The "positive Chvostek's sign" (contraction of facial muscles when the facial nerve is tapped) and "positive Oppenheim's sign" (contraction of the thumb when the dorsal surface of the hand is tapped) are indicative of neuromuscular excitability.
Diagnosis and Management
Diagnosis is primarily clinical, based on observation of signs and confirmation through serum calcium measurement. Treatment involves immediate intravenous calcium gluconate administration to rapidly raise serum calcium levels. Oral calcium supplements and dietary adjustments (increasing calcium and vitamin D intake) are also implemented for long-term management. Preventative measures are crucial, including ensuring adequate calcium intake during the dry period (pre-calving), supplementing with calcium salts (e.g., dicalcium phosphate) in the diet, and providing vitamin D supplementation.
Prevention and Control
A proactive approach to prevent HT is key. This includes:
- Careful diet formulation with appropriate calcium and phosphorus ratios.
- Supplementation with calcium and vitamin D during the dry period.
- Genetic selection for improved calcium metabolism.
- Monitoring calcium levels in high-risk animals.
Impact on Dairy Production
HT significantly impacts dairy production. Affected animals experience reduced milk yield, prolonged calving intervals, and increased susceptibility to other diseases. The cost of treatment and potential animal losses contribute to substantial economic losses for dairy farmers. According to the National Dairy Development Board (NDDB), HT is estimated to cost the Indian dairy industry millions of rupees annually.
Conclusion
Hypocalcemic tetany represents a significant challenge in dairy farming, demanding proactive management strategies. Early recognition of clinical signs, prompt treatment with calcium gluconate, and preventative measures focusing on dietary management and genetic selection are crucial for minimizing losses and ensuring sustainable dairy production. Continued research into the physiological mechanisms underlying HT and the development of more effective preventative strategies remain essential for optimizing the health and productivity of milch cattle.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.