Nickel in Cows’ Milk

Summary Nickelous chloride was fed as a supplement (500 mg. daily) to the rations of six cows for a period of 2 months by the double reversal method and the milk was analyzed for nickel. Although varying amounts of nickel were found in the numerous milk samples taken, it was shown that when the milk was kept from contact with metal by milking directly into glass jars, nickel was not present. Therefore it was concluded that nickel is not a constituent of natural milk and that the varying amounts found in the course of the investigation came from the milking machine. The difference in this respect between cobalt and nickel, two closely related elements, is discussed briefly.