ABSTRACT
The relation between the prevalence of contagious mastitis with the finding of Streptococcus agalactiae and Staphylococcus aureus and the number of somatic cells in the tank samples of milk was studied on the basis of a clinical and bacteriological examination of 11 129 daily cows on four large farms, with a capacity of 600 to 1240 animals. A statistically significant correlation was demonstrated between the analyzed characteristics (r = 0.621). The relation was demonstrated at a prevalence up to 25.3%. The number of somatic cells provides a marked indication of prevalence only from 10%. We failed to demonstrate a statistically significant correlation between the prevalence of mastitis with a cultivation finding of Staphylococcus aureus and the number of somatic cells in tank samples of milk (r = 0.054). The results suggest that on large farms it will not be possible to use only the number of somatic cells in tank milk samples as a signal of diagnostic improvement and preventive mastitis-control measures, since a 10% prevalence of these diseases usually excludes the possibility of herd sanitation.
