Final answer:
Sebaceous adenitis primarily affects dogs, a condition related to the inflammation of sebaceous glands which produce sebum, an essential substance for skin and hair lubrication.
Step-by-step explanation:
Sebaceous adenitis is a skin condition that affects the sebaceous glands of animals, leading to an inflammation that results in the reduction of sebum production. These sebaceous glands are important for producing sebum, an oily substance that helps to waterproof and lubricate the skin and hair. Among the animals prone to sebaceous adenitis are dogs, specifically certain breeds that are genetically predisposed to the condition. Sebaceous adenitis is less commonly reported in cats and is not a condition associated with horses or birds, as their skin structure and gland types differ significantly from those of mammals.