The effect of freezing of milk samples on the cultural results

152 quarter milk samples were examined microbiologically before and after storing at -80 deg C for 7 and 14 days. The total number of isolates from fresh milk (107) was higher than from frozen milk stored for 7 or 14 days (97 and 94 resp.). Similar numbers of staphylococci were isolated from fresh and frozen milk samples, whereas numbers of streptococci were slightly reduced in the frozen milk. The number of coliform isolates was not affected by freezing the milk samples. Examination of 158 composite milk samples for streptococci before and after freezing showed that of the 37 Streptococcus agalactiae, 7 Str. dysgalactiae and 3 Str. uberis strains isolated from fresh milk, 37 and 14 Str. agalactiae, 5 and 5 Str. dysgalactiae and 2 and 1 Str. uberis strains were isolated after 7 and 14 days resp. at -80 deg C. It is concluded that milk samples can be preserved at low temp. (-80 deg C) for 14 days without any change in the number of samples identified as positive for mastitis..