text: Cannulation requires installing a flanged rubber cylinder in the side of a cow, behind its 13th rib. The cylinder typically is fitted with a plastic, rubber, or metal cap to keep the rumen anaerobic.
  The rubber cannula is surgically implanted while the cow is standing and awake, with local anesthetic. The cow is made to fast and refrain from drinking water for 24 hours in advance of the surgery. Then the veterinarian excises a small piece of the cow's skin, makes an incision through the rumen, and stitches the open sides of the rumen to the edges of skin, to prevent the contents of the rumen from leaking into the rest of the abdominal cavity. Finally, the inner flange of the cannula is pushed inside the rumen and capped.