Somatic cell count in small ruminants: Friend or foe?

• DOI: 10.1016/j.smallrumres.2012.04.005
• Publication Date: 2012-05-22T06:24:04Z
• Authors: F.N. Souza; M.G. Blagitz; C.F.A.M. Penna; A.M.M.P. Della Li...; M.B. Heinemann; M.M.O.P. Cerqueira
• Keywords: Somatic Cell Count

Abstract Milk somatic cell counts are the basis of mastitis and milk quality control programs. Milk somatic cell counts for goats, in which neutrophils comprise the main cell type, are higher than those for sheep and cows. In cows, macrophages are the major cell type present in milk, as is the case for sheep. Milk secretion in small ruminants is apocrine in nature, and cytoplasmic particles, similar in size to milk somatic cells, are normal constituents of their milk, although concentrations of cytoplasmic particles are much higher in milk from goats than from ewes. This fact has led to the development of cell counting procedures that are specific for deoxyribonucleic acid to enable accurate milk somatic cell counts to be obtained. Furthermore, milk somatic cell counts in small ruminants are influenced by noninfectious factors such as lactation stage and parity. However, mastitis is the main factor that leads to an increase in somatic cell count due to the response to infection. There is some evidence that physiological variations in the viability, number and proportions of each leukocytes subpopulation may be related to mammary gland immune status, which is associated with periods of increased susceptibility to mastitis. The main etiological agent of mastitis in small ruminants is coagulase-negative staphylococci, and special attention should be paid to this group of bacteria. Unlike in cows, novobiocin-sensitive coagulase-negative staphylococci cause a significant increase in milk somatic cell counts. Finally, the somatic cell count and the California Mastitis Test represent valuable tools for mastitis screening and assessing the disease prevalence, but their predictive values are better in ewes than in goats.