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Variations in Alkaline Phosphatase Activity of Milk¹

Department of Dairying, University of Alberta, Edmonton, Canada

ABSTRACT

The phosphatase activity of milk, determined during one complete lactation period of individual cows, was found to vary from 119 to 4,380 phenol per 0.5 ml. of milk. Minimum and maximum values occurred approximately 1 week and 28 weeks after parturition, respectively. Enzyme concentration was related inversely to milk yield, but no correlation was observed between phosphatase and breed, fat percentage, or feed. Maximum total phosphatase production per milking was reached approximately 24 weeks after parturition.

During a complete year the phosphatase activity of pooled milks, representative of approximately 500 cows, ranged from 950 to 1,700 phenol per 0.5 ml. of milk. The trend corresponded to that observed during the lactation of individual cows, with maximum values occurring in early winter. Variations in initial phosphatase activity could influence the heat treatment required to inactivate the enzyme to the Sanders and Sager pasteurization standard.

¹ The data are part of a thesis presented by the senior author in partial fulfillment of the requirements for the degree of Master of Science at the University of Alberta.

² Present address: University of California, Davis.