Herd incidence of bovine mastitis in four danish dairy districts. III. Relation between frequency of mastitis and cell counts on bulk molk samples.

: The correlations between monthly bulk milk cell counts and the actual frequency of mastitis was investigated in 399 Danish dairy farms with a total of about 7000 cows. The correlation coefficients varied from 0.3 to 0.5. Correlations were improved by using more than one cell count, but not further improved by using more than two cell counts. The correlations were higher for large than for small herds. It was not possible by combining cell counts in different ways, as indicated in (Table IV, to point out every heavily mastitis-affected herd without also pointing out some not so heavily affected ones. Table IV shows what infection levels can be expected when different criteria based on bulk milk cell counts are applied. The figures cannot be transferred directly from Danish conditions to conditions in other countries, but similar tendencies can probably be found anywhere.