In the absence of gross pathological and bacteriological indicators, histopathology was used as the most sensitive technique to determine the risk of potential bacteraemia in the very young slaughter calves with and without lesions of localized navel ill (omphalophlebitis). The positive predictive value (ability to detect truly diseased cases) of routine post-mortem meat inspection for the detection of localized navel ill was 87.4% and the negative predictive value (ability to detect truly non-diseased cases) was 98.1%. The probability of histopathological lesions suggestive of bacteraemia in the kidneys and/or liver of calves with localized navel ill (319 cases) was 0.29 [0.24, 0.34] whereas that in control carcasses (319 cases) was 0.21 [0.17, 0.25]. There was no statistically significant difference in the proportion of cases graded as having severe compared with moderate periportal hypercellularity of the liver in each group. The risk of potential bacteraemia in carcasses passed at routine post-mortem meat inspection according to two different judgement regimes for localized navel ill (condemnation vs trimming of localized lesions) was virtually identical (251 vs 254 per 1000 carcasses passed respectively) and was not sensitive to changes in the prevalence of localized navel ill.
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