From unloading to trimming: studying bruising in individual slaughter cattle.

Livestock bruising is both an animal welfare concern and a detriment to the economic value of carcasses. Understanding the causes of bruising is challenging due to the numerous factors that have been shown to be related to bruise prevalence. While most cattle bruising studies collect and analyze data on truckload lots of cattle, this study followed a large number (n = 585) of individual animals from unloading through postmortem processing at five different slaughter plants. Both visual bruise presence and location was recorded postmortem prior to carcass trimming. By linking postmortem data to animal sex, breed, trailer compartment, and traumatic events at unloading, a rich analysis of a number of factors related to bruise prevalence was developed. Results showed varying levels of agreement with other published bruising studies, underscoring the complexity of assessing the factors that affect bruising. Bruising prevalence varied across different sex class types (P < 0.001); 36.5% of steers [95% confidence interval (CI): 31.7, 41.6; n = 378], 52.8% of cows (45.6, 60.0; 193), and 64.3% of bulls (no CI calculated due to sample size; 14) were bruised. There was a difference in bruise prevalence by trailer compartment (P = 0.035) in potbelly trailers, indicating that cattle transported in the top deck were less likely to be bruised (95% CI: 26.6, 40.4; n = 63) compared to cattle that were transported in the bottom deck (95% CI: 39.6, 54.2; n = 89). Results indicated that visual assessment of bruising underestimated carcass bruise trimming. While 42.6% of the carcasses were visibly bruised, 57.9% of carcasses were trimmed due to bruising, suggesting that visual assessment is not able to capture all of the carcass loss associated with bruising. Furthermore, bruises that appeared small visually were often indicators of larger, subsurface bruising, creating an "iceberg effect" of trim loss due to bruising.

Identification of Escherichia coli O157:H7 surrogate organisms to evaluate beef carcass intervention treatment efficacy.

We compared the survival of potential pathogen surrogates-meat-hygiene indicators (non-Escherichia coli coliforms), biotype I E. coli, and lactic acid bacteria starter cultures-with survival of an E. coli O157:H7 (ECO157:H7) inoculum in beef carcass intervention trials. Survival of one lactic acid bacteria starter culture (Bactoferm LHP Dry [Pediococcus acidilactici and Pediococcus pentosaceus]), a five-isolate biotype I inoculum, and a five-isolate non-E. coli coliform inoculum, was compared with survival of a 12-isolate ECO157:H7 inoculum in interventions by using beef brisket (adipose and lean), cod fat membrane, or neck tissue. Treatments were grouped by abattoir size: small (6-day dry aging; 22°C acid treatment [2.5% acetic acid, 2% lactic acid, or Fresh Bloom], followed by 1-day dry aging; hot water) and large (warm acid treatment [5% acetic acid or 2% lactic acid] with or without a preceding hot water treatment). Reductions in pathogen and surrogate inocula were determined with excision sampling. A surrogate was considered a suitable replacement for ECO157:H7 if the intervention produced a reduction in surrogate levels that was not significantly greater (P≥0.05) than that observed for ECO157:H7. All three surrogate inocula were suitable as ECO157 surrogates for dry aging and acid spray plus dry-aging treatments used by small abattoirs. No one inoculum was suitable as an ECO157 surrogate across all intervention treatments used by large abattoirs. Effects seen on neck tissue were representative of other tissues, and the low value of the neck supports its use as the location for evaluating treatment efficacy in in-plant trials. Results support using nonpathogenic surrogate organisms to validate beef carcass intervention efficacy.

Manual squeezing as an alternative to mechanical stomaching in preparing beef carcass sponge samples for microbiological analysis.

The U.S. Department of Agriculture (USDA) requires beef abattoir operators to periodically analyze beef carcass sponge samples for levels of Escherichia coli. Additional beef carcass sponge sampling is commonly used by processors to evaluate the efficacy of beef abattoir antimicrobial intervention systems. The USDA sample preparation procedure requires that beef carcass sponge samples be mechanically stomached for 2 min before the sample fluid is squeezed out for analysis. When a large number of sponge samples must be analyzed, the stomaching step can limit throughput. In this study, we compared the USDA sample preparation procedure with repeatedly squeezing the sponge during a 10-s interval to expel the sample fluid. Separate sponge samples were obtained from each half of 100 chilled postintervention beef carcasses from a large-volume abattoir during a 4-month period. The USDA and squeezing treatments were randomly assigned to the halves of each carcass. All sponge samples were analyzed for E. coli, coliforms, Enterobacteriaceae, and aerobic mesophilic bacteria using Petrifilm methods. The sample preparation method had no significant effect (signed rank value > 0.05) on the results of any analytical test, although aerobic mesophilic bacteria counts tended to be higher after the USDA method than after manual squeezing alone. These results suggest that manual squeezing may be a simple and rapid alternative sample preparation method when gram-negative bacteria such as E. coli, coliforms, or Enterobacteriaceae are being enumerated from beef carcass sponge samples used to monitor operational abattoir hygiene.