What is the most likely cause of patchy alopecia around the eyes and ears in a 10-month-old Angus steer?

The presence of patchy alopecia around the eyes and ears of a young Angus steer is most consistent with dermatophytosis, which is a fungal infection caused by dermatophytes. This condition is commonly known as ringworm. In young animals, like this 10-month-old steer, dermatophytosis is particularly prevalent as their immune systems are still developing, making them more susceptible to fungal infections. The lesions typically present as circular patches of hair loss, and they can often appear around the face, ears, and elsewhere on the body.

Dermatophytosis can be spread through direct contact with infected animals or contaminated environments. The characteristic appearance of the alopecia in localized areas, especially on the head and ears, aligns well with the clinical signs of this infection. Additionally, the age of the steer supports this diagnosis since younger animals tend to be more vulnerable.

While other conditions listed can also cause hair loss, their clinical presentations are not as fit for the symptoms described in this case. For example, contagious ecthyma primarily affects the lips and mouth rather than causing alopecia, while copper deficiency typically leads to a general thinning of hair rather than patchy loss. Dermatophilosis is more associated with exudative dermatitis rather than localized