Variability and Determinants of Carcass Bacterial Load at a Poultry Abattoir

Roaster chicken carcasses (2,928) were collected from the evisceration line of a poultry abattoir over a 5-month period and identified as to the lot (truck load) and supplier. Bacterial load was determined by mechanically rinsing each eviscerated carcass in sterile water and then using an automated hydrophobic grid membrane interpreter system to obtain the log₁₀ most probable number of aerobic bacteria per gram of carcass. Analysis of variance demonstrated that the between-carcass, between-lots-within-supplier, and between-supplier components of variability in bacterial load represented 73.2, 14.2, and 12.6% of the total variability, respectively. There was a significant (p < 0.001) supplier and lots-within-supplier effect on bacterial load of carcasses. A regression model demonstrated that bacterial load of lots significantly (p ≤ 0.05) decreased with increasing hours of operation of the evisceration line. Factors in the model which were significantly (p ≤ 0.05) associated with increased bacterial load included longer crating and holding times, higher visible contamination scores, slaughter during winter months, higher outdoor temperatures, and slaughter of lots composed of only pullets. The model explained about 23% of the variability in bacterial load.