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
