Relationship between total bacteria counts and somatic cell counts from mammary quarters infected by mastitis pathogens

Abstract

This study was conducted to establish the relationship between somatic cell count (SCC) and bacterial shedding from mammary quarters according to mastitis pathogens. Milk samples from 638 mammary quarters were examined for mastitis pathogens, SCC and total bacterial count (TBC). The raw data of SCC and TBC were used to perform descriptive statistics. The significance of the arithmetic mean differences between SCC and TBC according to bacteriological examination results was determined by a two-tailed unpaired t-test. Pearson and Spearman´s correlations were done with logarithmic data and linear regression analyses. The geometric means of the bacteriological examination results were (cells mL-1; CFU mL-1): no growth (52,000; 12,000), coagulase-negative staphylococci (85,000; 17,000), Staphylococcus aureus (587,000; 77,000); other streptococci (432,000; 108,000) and Streptococcus agalactiae (1,572,000; 333,000). The Pearson and Spearman's correlations between SCC and TBC were higher than 0.60 for all mastitis pathogens. The regression analyses slopes showed different increase in TBC with the same increase in SCC according to mastitis pathogens. The slope for S. agalactiae (0.542) was higher than that for other mastitis pathogens. The results suggest that the intensity of inflammatory process was associated with number of mastitis pathogens shedding from the mammary gland.