THE DETECTION OF ABNORMAL COW'S MILK BY MICROSCOPIC METHODS

Abstract

A large number of milk samples from dairy cows have been studied microscopically and culturally, the object being to estimate the numbers of body cells and leucocytes present.The Breed and sediment counts are compared. The latter is preferred because it furnishes more information than mere enumeration of the cells. In a sediment smear a complete picture of conditions in the udder may be visualized, including the various cellular responses to the organisms causing mastitis. Estimates of the numbers of cells present are sufficient for a diagnosis when accompanied by the information gained in examining the smear.Differential counts were made for special purposes only, such as to define normality in milk. In defining normal milk, a standard was set which did not tolerate the presence of micro-organisms or polymorphonuclear leucocytes in the samples. In a herd of 60 cows, milk from 9 young cows met this standard. Diphtheroids occurred in 70% of the cows. In comparison with the clean cows, the diphtheroid carriers had larger numbers of polymorphonuclear leucocytes.In staphylococcic mastitis the leucocytes are often very numerous, and this may persist for months. Staphylococcic infections cause a great influx of large, ring-shaped polymorphonuclear leucocytes. The cocci can generally be found on the smears. Sometimes, when leucocytes are scarce, cocci occur in very large numbers.In streptococcic mastitis the mononuclear leucocytes are numerous. Loose, irregular clumping is commonly seen, and the polymorphonuclear leucocytes often clump separately. Leucocytes are not as numerous as in staphylococcic cases, but the percentage of the mononuclear leucocytes is higher. Tables showing the increase and decrease of the leucocytes indicate that when they are numerous the infective organisms may be scarce or absent, the reverse being also true. Streptococcic mastitis is sometimes a difficult disease to diagnose microscopically, on account of scarcity of organisms. Various ways of finding the cocci are discussed.The diagnosis of B. coli and Corynebacterium pyogenes mastitis is described. Both these organisms may cause severe lesions, and consequently the smears reveal extensive degenerative changes in the leucocytes. The organisms are present in large numbers. B. coli and C. pyogenes infections produce a different leucocytic picture under the microscope than do pyogenic cocci. The effect of these infections is generally more destructive.A study of phagocytosis in diseases of the udder furnishes valuable aid in determining the degree of resistance to infection on the part of the host.Red blood corpuscles in milk may be unaccompanied by any signs of infection. Chromatin-staining granules in milk are caused by degenerative changes in the polymorphonuclear cells. Calcium calculi are found both in the tissues and in the milk. A study of over 20 samples of colostrum is recorded.