Correct Option: D. Blood stained diarrhea Explanation of the Correct Answer: Foot and mouth disease (FMD) is a highly contagious viral disease that primarily affects cloven-hoofed animals, including cattle. The symptoms of FMD are well-documented and include:

1. Excessive Production of Saliva (Option A): One of the hallmark symptoms of FMD is the excessive salivation due to the formation of painful sores in the mouth. The lesions can make it difficult for the animal to swallow, leading to drooling.
2. Sores on Feet and Tongue (Option B): FMD is characterized by the development of vesicular lesions (blisters) in the mouth, on the tongue, and on the feet. These sores can cause significant pain and discomfort, affecting the animal's ability to eat and walk.
3. Lameness (Option C): Lameness is a common symptom associated with FMD due to the painful lesions that develop on the feet. The animal may avoid putting weight on the affected limbs, leading to noticeable lameness.
4. Blood Stained Diarrhea (Option D): This option is not a symptom of foot and mouth disease. While gastrointestinal symptoms can occur in some diseases, blood-stained diarrhea is not typically associated with FMD. Instead, it is more commonly linked to other conditions such as certain bacterial infections or parasitic infestations.

Why the Other Options are Incorrect or Weaker:

• Option A (Excessive Production of Saliva): This is a classic symptom of FMD. The presence of excessive saliva is directly related to the painful lesions in the mouth, making this option a strong indicator of the disease.
• Option B (Sores on Feet and Tongue): This is another definitive symptom of FMD. The presence of sores is a key diagnostic feature of the disease, making this option correct.
• Option C (Lameness): Lameness is a direct consequence of the painful lesions on the feet caused by FMD. It is a common symptom and is often used to identify the disease in affected herds.

Summary of Key Points:

• Foot and mouth disease is characterized by excessive salivation, sores in the mouth and on the feet, and lameness.
• Blood-stained diarrhea is not a symptom of FMD and is associated with other diseases.
• Recognizing the correct symptoms is crucial for diagnosis and management of FMD in cattle.

Revision Summary:

• FMD symptoms include excessive salivation, sores on feet and tongue, and lameness.
• Blood-stained diarrhea is not a symptom of FMD.
• Understanding the symptoms helps in the early detection and management of the disease.
• Accurate diagnosis is essential for controlling the spread of FMD in livestock.