Question

Deficiency of thiamin in chicken results in

• A. Star grazing symptom
• B. Encephalomalacia
• C. Nutritional roup
• D. Dermatitis

Hint:

Remember the classic neurological association of Thiamin:
- Humans \(\rightarrow\) Beriberi Wernicke-Korsakoff syndrome.
- Cattle \(\rightarrow\) Polioencephalomalacia.
- Chicks \(\rightarrow\) Polyneuritis resulting in "Stargazing."

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Vitamins are essential organic micronutrients required for key metabolic pathways. In poultry, vitamins must be supplied in precise amounts in the feed, and deficiencies produce highly characteristic clinical symptoms.

Step 2: Detailed Explanation:
Let us analyze the deficiency symptoms associated with each option:

Option (A): Star grazing symptom: Thiamin (Vitamin \(B_1\)) acts as a coenzyme (thiamin pyrophosphate) in carbohydrate metabolism, particularly in decarboxylation reactions.
Because nervous tissue relies almost entirely on carbohydrate metabolism for energy, thiamin deficiency leads to rapid neurological decline.
In chicks, this manifests as extreme polyneuritis, causing spastic paralysis of the neck muscles.
The chick pulls its head backward and upward, looking directly at the sky, a clinical posture known as the "stargazing" symptom. Thus, this is the correct choice.

Option (B): Encephalomalacia: Also known as "crazy chick disease," this is caused by a deficiency of Vitamin E. It results in hemorrhages and edema in the cerebellum, leading to uncoordinated movement and prostration.

Option (C): Nutritional roup: This is caused by a deficiency of Vitamin A. It leads to squamous metaplasia of the mucous membranes, particularly in the eyes, nasal passages, and upper digestive tract, producing discharge similar to infectious coryza (roup).

Option (D): Dermatitis: Severe dermatitis (crusty lesions around the eyes, beak, and feet) is a classic symptom of biotin or pantothenic acid deficiency.
Therefore, thiamin deficiency is specifically linked to the star grazing symptom.

Step 3: Final Answer:
The correct option is (A).