A cow starts to give milk between the ages of two and two-an-a-half years, after the birth of its first calf. For the first few days the milk is unfit for human consumption and is fed to the calf which is afterwards reared separately. During the milking or lactation period that follows the cow’s yield usually reaches a maximum after four to six weeks and continue in decreasing quantities for nine to ten months.
To ensure a steady supply of milk, farmers arrange for their cows to calve every 12 months. Attention to breeding has led to steady improvements in yields. A good cow may produce up to 2,000 gallons during the lactation period.
Cows are normally milked twice a day, morning and evening. Except for the smallest herds, milking in advanced countries is usually done by machines which suck the milk from the cows’ udders and transfer it to covered containers. But there are still many countries where milking is largely done by hand, in the traditional way.