Risk Assessment: Abscessation of Head Lymph Nodes and Carcass Inspection at Two High-Line-Speed Beef Abattoirs in Western Canada.

Canadian inspection procedures for railing out young beef heifer and steer carcasses in high-line-speed abattoirs because of head lymph node abscessation (HLNA) were evaluated. A total of 231,405 animals were inspected and 3,368 that had HLNA were railed out to a stationary line and subjected to further detailed examination. These were compared to 1,659 control carcasses lacking any visual abnormalities, including HLNA, in the judgment of inspection personnel. Four carcasses and 7 portions of carcasses with HLNA and 2 portions of control carcasses were condemned. Histopathological and limited bacteriological examinations were carried out. It was concluded that use of HLNA detection exclusively for more detailed carcass inspection was inefficient and lacked scientific validity. Other criteria are essential for the identification of carcasses that pose a significant hazard to human health.

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.

Verification of the level of Microbiological Control for the Slaughter and Cooling Processes of Beef Carcass Production at a High-line-Speed Abattoir.

Methods are described which were used to verify the microbiological adequacy of the processes of production and chilling of carcasses at a high-line-speed abattoir. Ten excision samples (5 by 5 by 0.2 cm) were taken from each of 16 to 20 carcasses for each evaluation of these processes. Twelve monthly evaluations were made for the slaughter of steers, heifers, and cows and additional evaluations for each of the slaughter of cows and the chill process of carcasses. The ranges of the estimated mean log10 most probable number of growth units per square centimeter (LMPN, for 236 carcasses) and Escherichia coli per square centimeter (LEC, for 240 carcasses) enumerated by hydrophobic-grid membrane filter technology for the 12 monthly evaluations of the slaughter floor were 1.11 to 1.62 (LMPN) for single samples and 0.20 to 0.65 (LEC) for pooled samples. Based on a published advisory scale for the slaughter floor the aerobic bacterial counts reflect a cleanliness level of "excellent" to "good." For single evaluations of cow carcasses at the end of slaughter and of chilled carcasses the mean LMPN was 1.78 ("good") and 1.40 respectively. From pooled samples of each of the 236 steer, heifer, and cow carcasses the pathogen E. coli O157:H7 was identified by polymerase chain reaction on one carcass whereas Listeria monocytogenes was identified on 14 carcasses. Verocytoxigenic E. coli (6 isolates) and L. monocytogenes were not isolated from the same carcasses. These low isolation rates dictate a large sample size and therefore these pathogens are excluded from use to routinely verify the workings of hazard analyses and critical control point (HACCP) systems for beef slaughter processes in Alberta. Alternatively the use of aerobic bacterial counts to directly measure cleanliness or of E. coli counts to indirectly measure fecal contamination appears to be more practical than the use of specific pathogen counts for regulatory agencies to verify the workings of quality control programs, including HACCP systems.

Visual Demerit and Microbiological Evaluation of Beef Carcasses: Methodology.

A repeatable, automated method was developed for estimating aerobic bacterial populations on surfaces of groups of beef carcasses. Ten sample cluster sites (CS) were identified by localizing visual demerits (Canadian Streamlined Inspection System) on 200 carcasses at one plant. Most probable number growth units per cm2 (MPNGU/cm2) on hydrophobic grid membrane filters (HGMF) were assessed by an automated HGMF interpreter for excision samples from the centers of these CS. Between-sample variation of more than 90% of the total log10 MPNGU/cm2 variance indicated good repeatability between HGMF of the same sample and interpretations of the same HGMF. Variance component estimates indicated that there was considerable variation in MPNGU/cm2 between carcasses and between paired adjacent samples for a CS. A statistically significant but weak association was found between the demerit scores of a CS and MPNGU at its center. The variance component estimates will be used to estimate the sample size required for future group-carcass evaluations.