An investigation of a milk-copper sulphate reaction as a pregnancy test in cows

Milk samples were collected from Holstein and Jersey cows in the University of Tennessee Experiment Station, Knoxville, dairy herd for an investigation of the reliability of a milk-copper sulphate reaction as a method for early diagnosis of pregnancy in cows. A total of 139 cows were used in this study. Trial I involved the collection of milk samples without reference to breeding records. In Trial II milk was collected at regular intervals from two weeks, postinsemination, through the 65th day. Subsequent to the collection of milk samples and over-night refrigeration, the test was performed using 0.1 ml of milk and 5% copper sulphate. The diagnosis was based on the direction and rate of movement of the milk coagulum in the copper sulphate solution and compared with the results of rectal palpation. The apparent accuracy of 60-75% (21-55 days postinsemination) is encouraging, however, the fact that approximately one third of the nonbred cows yielded a positive test and only 47% of the inseminated cows yielded a positive test raises questions as to the validity of the test in detecting early pregnancy in cows. Further refinements of the test to improve its accuracy are necessary before it can be recommended as a method for pregnancy dia-gnosis under commercial herd conditions.