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 . Other nerves send messages from the udder and other parts of the body to the brain about touch, temperature and pain. The body then releases hormones which also control blood flow and milk production. This helps milk let-down . 36 Excitement and pain also send messages to the brain.