Aavin is a major cooperative society in Tamil Nadu involved in:

Milk procurement and processing
Fodder production
Veterinary services
Livestock breeding

Aavin is a major cooperative society in Tamil Nadu involved in milk procurement and processing. It was established in 1958 with the objective of providing a remunerative price to milk producers and to ensure the availability of quality milk to consumers. Aavin procures milk from over 1.5 million milk producers in Tamil Nadu and processes it into a variety of products, including milk, milk powder, ghee, butter, and cheese. Aavin also provides veterinary services to milk producers and conducts research on dairy development.

Option (a) is the correct answer. Options (b), (c), and (d) are incorrect because Aavin is not involved in fodder production, veterinary services, or livestock breeding.