Use of Holstein Cattle: Holsteins are one of the largest dairy breeds; they're large not only in size but in milk production. The average Holstein in a commercial dairy produces 24,000 pounds of milk per year with 2.5 to 3 percent butterfat—that's about 10 gallons of milk per day. Of the over 9 million cows regularly milked in the United States, about 90 percent are Holsteins. Photo by Daniel Broussard.