From the 1950s, Norwegians started adding iodine to dairy cow feed. Dairy cow diets contain corn and corn silage. The rumen is a micro-ecosystem within each dairy cow. Rear feet and legs are given 20% of the overall preference of a dairy cow. Female calves will become a replacement dairy cow. These are also given on the Dairy Cow Unified Scorecard. A two-part stamp featuring a dairy cow was issued around 1930. Frame is given the lowest level of importance on the Dairy Cow Unified Scorecard. The dairy cow produces large amounts of milk in its lifetime. To maintain lactation, a dairy cow must be bred and produce calves. Over the centuries, the result was a high-producing, black-and-white dairy cow. A dairy cow called Lily Flagg broke the world record for butter production in 1892. An average dairy cow begins her lactation with a moderate daily level of milk production.