The accuracy of various sampling methods in raw whole milk received at a milk processing plant from dairy farms was compared. Milk samples were collected daily during four 30-day periods representing approximately the four seasons of the year. The Babcock test for butterfat was applied to the following: daily samples, 6-day composite samples without added preservative, seven and 15-day preserved composite samples and periodic samples taken three, four and five times per month. The preservatives, Milkeep and mercuric chloride, were compared in the seven and 15-day composite sample. The daily test, recognized for its accuracy, was used in statistical comparison with the test results from the other samples. When the tests from each sampling method were averaged for the four seasons, no significant differences were found. Tests from the 6-day composite samples and the periodic samples taken five times per month were identical to the daily test. Tests from composite samples preserved with Milkeep averaged closer to the daily test than did those preserved with mercuric chloride in both the seven and 15-day composite samples.
1A grant from the Arizona Dairymen's League aided in the financial support of this project. In Januray, 1960, a merger of the Arizona Milk Producers and the Arizona Dairymen's League brought about a new organization which is now called the United Dairymen of Arizona.