They damage the stomach and intestinal lining.
Explanation
Parasites affecting cattle are broadly classified into external parasites (ectoparasites) and internal parasites (endoparasites). The specific health impact on the animal depends on the location where the parasite resides and feeds.
Analysis of Options:
- They cause cutaneous diseases. is incorrect: Cutaneous (skin) diseases are primarily caused by external parasites such as lice, ticks, and mites, which live on the skin surface.
- They damage the stomach and intestinal lining. is correct: Internal parasites, particularly worms (such as roundworms and tapeworms), primarily inhabit the digestive tract. They damage the lining of the stomach and intestine, interfering with digestion and nutrient absorption.
- They impair the respiratory system. is incorrect: While specific parasites like lungworms can affect the respiratory system, the general classification of internal worms in the context of cattle health is most commonly associated with gastrointestinal damage.
- They reduce the reproductive capacity. is incorrect: Reduced reproductive capacity is often a secondary effect of poor nutrition or specific reproductive diseases, rather than the primary direct injury caused by common internal worms.
Key Takeaway:
In cattle, external parasites cause skin diseases, whereas internal parasites like worms affect the stomach and intestine, and flukes damage the liver.