No abstract

SUMMARY: A field‐scale experiment carried out in Wales and the West Midlands, in which the temperature‐compensated clot‐on‐boiling (C.O.B.) test of Rowlands & Hosking (1951) was applied to 11,626 samples of designated milk, morning, mixed and evening milk, gave proportions of failures in the ratio 1:2:3 respectively. Despite temperature compensation, failures varied according to atmospheric temperature from c. 50% at 72°F. or more to 10% at 56°F. or less and averaged 20% during the summer and 7% during the six winter months. No marked differences were noted between the keeping qualities of tuberculin tested or accredited milk. During the winter no difference was found between producer‐wholesaler and producer‐retailer supplies, but the latter had a higher proportion of failures of evening and mixed milks during the summer. In a set of 8,297 samples examined in addition by the methylene blue and coli‐aerogenes tests, the C.O.B. test gave a lower incidence of failures than either the methylene blue or combined methylene blue and coli‐aerogenes tests throughout almost the entire year. It is suggested that a temperature‐compensated C.O.B. test is practicable as a routine procedure.