VARIABILITY IN BROILER CARCASS BACTERIAL LOAD AT 3 ABATTOIRS, AS MEASURED BY A HYDROPHOBIC GRID MEMBRANE-FILTER INTERPRETER

In this observational study, the variability of broiler carcass bacter ial load was investigated at three federally inspected abattoirs, usin g an automated hydrophobic grid membrane filter interpreter system. Th e measurement protocol involved: whole carcass rinses aided by a mecha nical carcass shaker; filtration of rinse solutions through hydrophobi c grid membrane filters (HGMF) (ISO-GRID(R), QA Laboratories, Ltd., To ronto, Ont.); and use of an automated HGMF interpreter (MI-100 HGMF In terpreter System, Richard Brancker Research, Ltd., Ottawa, Ont.). Carc ass and lot mean bacterial loads were measured, respectively, in units of log10 most probable number (MPN) of mesophylic aerobic colony form ing units per gram of carcass (LgMPN/g), and slaughter lot mean LgMPN/ g (LMLgMPN/g). Whole carcass rinses were conducted on a total of 1,917 carcasses, among % slaughter lots from three abattoirs. Overall, the LgMPN/g ranged from 1.054 to 4.180 with a mean of 2.585 and a variance of 0.263. These corresponded to MPN/g counts from 11 to 15,135 and a geometric mean of 385 MPN/g. Statistically significant differences wer e observed between abattoirs and between lots within abattoirs. The in tra-abattoir correlation coefficient of LgMPN/g was r = 0.180 (p < 0.0 01). The within abattoir intralot correlation coefficient was r = 0.25 9 (p < 0.001). In this data set, approximately 56, 26, and 18% of the variability in LgMPN/g were attributed to factors operating at the ind ividual bird, lot, and abattoir levels of organization, respectively. Factors significantly associated with LMLgMPN/g included: abattoir (p < 0.001), transportation time from farm to abattoir (p < 0.001), and w aiting time from arrival at the abattoir yard to actual slaughter (p = 0.002). Analysis of a series of five repeat rinses, conducted on one bird from each of the 96 study lots, demonstrated that bacterial count s in the second to fifth sequential rinses were positively associated with the bacterial count of the first rinse. Also, after adjusting for the initial count, a pattern of decreasing counts was observed in sub sequent rinses.