These ducts only store and drain milk. The streak canal secretes a liquid which fights bacteria. A muscle closes the streak canal. If the muscle is loose , milking is faster but it is easier for the cow to get udder infections. Arteries carry blood from the heart to the udder and carry food and oxygen .
Veins carry blood with waste products away from the udder.
Looking from the back, you can see the milk veins and other veins and the middle ligament . 33 Blood flow is important for milk production. About 500 l of blood must flow through the udder to produce 1 l of milk. Some nerves send messages from the brain to the udder. This controls blood flow and milk production .