 This daily milking routine goes on for about 300 to 320 days per year that the cow stays in milk.Some small herds are milked once a day for about the last 20 days of the production cycle but this is not usual for large herds.If a cow is left unmilked just once she is likely to reduce milk-production almost immediately and the rest of the season may see her "dried off" (giving no milk) and still consuming feed.