For dairy farming and other livestock, I suggest you use
1. Livestock Production management by NSR Sastry and CK Thomas
2. Principles of animal nutrition and feed technology by DV Reddy.
I think this gives you a very clear idea about feeding and managing diseases of cows.
Also check out the website
Hoards, its an american website. They have some publications which are very good. You have to order online and they send to your address.
Happy Reading.
Nikhil