How does a cow make milk? It all starts with blood — and a lot of it. To produce just 1 gallon of milk, a cow must pump about 400–500 gallons of blood through her udder. Why? Because blood brings everything needed for milk production: 🐄 Nutrient delivery: Blood carries essential nutrients like glucose, amino acids, fatty acids, vitamins, and minerals to the udder. These are the raw materials that mammary cells use to build milk. 🐄 Oxygen supply: Just like any working organ, the udder needs oxy