Preslaughter Hide Status of Cattle and the Microbiology of Carcasses

An assessment was made of the association between tag (mud, bedding, and manure) attached to hides of beef cattle at slaughter and bacterial deposition on carcasses. A total of 624 carcasses from 52 lots of cattle in southern Alberta from January to June 1996 were studied at a high-line-speed abattoir (HLSP) which processed 285 carcasses per h and at a slow-line-speed abattoir (SLSP) which processed 135 carcasses per h. Tag was quantitatively assessed on the belly, legs, and sides of 12 carcasses per lot by the same project worker (lot tag score) and for each incoming lot of cattle by plant personnel (plant lot tag score). Swabs (approximately 10 by 10 cm) were taken from the medial rump and sacrum immediately after hide removal and from the brisket and top of shoulder after carcass splitting. These samples were pooled for each carcass and aerobic mesophilic bacteria, coliforms, and Escherichia coli were enumerated. The lot bacterial count was calculated by averaging the individual bacterial results of the 12 carcasses in a lot. At the HLSP, the lot side scores and the plant lot tag scores were negatively associated (P < 0.05) with the aerobic bacteria, coliforms, and E. coli . Counts were lower when tag was shaven off of the hides or when the line speed was slowed, but the reductions in counts were less than 0.5 log₁₀/cm². At the SLSP, the lot belly score was negatively associated (P < 0.003) with the aerobic bacterial counts. Neither the lot tag score nor the plant lot tag score were associated (P > 0.05) with the bacterial counts. Surface wetness of the hides was weakly (P < 0.05) associated with coli forms and E. coli counts. This study indicates that there is no consistent association between lot tag scores, plant lot tag scores, and bacterial contamination of carcasses. Changes in bacterial counts when associated with lot tag scores, plant lot tag scores, surface wetness of hides, line speed, or shaving off of tag were generally less than 0.5 log₁₀/cm². Thus, these variables are individually assessed as control points, but not critical control points of HACCP plans for the prevailing beef slaughter processes (including line speed adjustment at the HLSP) at the two plants studied.