Dairy cattle evaluation is the process of placing a group of dairy cows in order from most to least desirable based on milk production and longevity, where each animal is compared against the "ideal" animal. Dairy cattle are evaluated based on physical traits that equate to high milk production, with slight variations between different breeds. Dairy cattle evaluation is primarily used by producers to select the best cows to keep in the herd. Evaluation by country United States In the U.S., the standard for dairy cattle evaluation is provided by the Dairy Cow Unified Scorecard, created by the Purebred Dairy Cattle Association. (PDCA) This system of evaluation is the industry standard, and is advised by the Holstein Foundation, Holstein UK, the FFA and 4-H Organizations, and the World Dairy Expo. There are nationwide dairy cattle evaluation contests held by groups such as the National FFA Organization and 4-H, as well as at large dairy shows like the World Dairy Expo and the All-American Dairy show. These contests attract a wide range of evaluators, from high school to post-secondary education age. These contests generally place cows in groups of four, called classes. Each class is made up of cows of the same age and breed. The 7 breeds recognized by the PDCA are: Ayrshire, Brown Swiss, Guernsey, Red and White, Holstein, Jersey, and Milking Shorthorn. The major points considered when evaluating dairy cows are divided into 4 major categories: Frame, Dairy Strength, Rear Feet and Legs, and Udder. Each of the four categories is additionally subdivided into specific traits, and given a specific weight when evaluating dairy cattle. Although judgers reference the scorecard when evaluating cattle, the memorization of the weights of each trait gives them a way to determine the most desirable cow. Udder - 40% Because the primary product of a dairy cow is milk, the udder traits are most heavily weighted. Udder depth is the most important trait of the udder. It is assigned a maximum of 10 points. The udder should not be carried too high nor too low. The floor of the udder should be carried at a depth near the hock of the animal. The appropriate depth of the udder helps to prevent mastitis, but also ensures that the animal can carry the most milk. Udder depth is related to the number of lactations of a cow, and this is taken into consideration. The rear