Simplified resazurin rennet test for diagnosis of mastitis.

A simplified resazurin rennet test for diagnosis of bovine mastitis was devised. A tablet of resazurin and rennet was placed in a sterile test tube to which 10 ml of milk were added directly from a teat. The test tube was incubated for 1 h at 37 C. After incubation the change in color of resazurin and the time required for coagulation by the rennet were observed. From the results the milk samples tested were classified into four types. Cell count, modified California Mastitis Test, coagulase positive staphylococci, and contents of solids-not-fat, lactose, and protein differed among the four types. This method is simple and practically useful for diagnosis of bovine mastitis.