What condition is characterized by inflammation of the mammary gland, particularly in dairy cows?

Mastitis is characterized by inflammation of the mammary gland, which is particularly significant in dairy cows. This condition is often caused by bacterial infections, but it can also result from non-infectious factors. In dairy farming, mastitis is a major concern as it affects milk production and quality, leading to economic losses and requiring careful management and treatment strategies. The inflammatory process can result in various clinical signs, including swelling, heat, pain in the affected gland, and changes in the milk, such as increased somatic cell counts or the presence of clots.

The other conditions mentioned do not relate to the mammary gland: arthritis involves inflammation of the joints, conjunctivitis refers to inflammation of the conjunctiva in the eye, and Rickettsia represents a genus of bacteria associated with specific infectious diseases, not with inflammation of the mammary gland. Thus, the definition and implications of mastitis clearly align it as the correct answer.