Mammary gland exposure of cows to Mycobacterium paratuberculosis.

Mycobacterium paratuberculosis injected into the mammary gland was transported to the supramammary lymph nodes in 5 of 6 cows and to the intestine of 1 cow. The bacillus caused hypersensitivity to johnin and stimulated the production of complement-fixing antibodies. Apparently, the bacillus is not a cause mastitis.