Effect of free range production system on safety and microbiological parameters of poultry carcasses

A study was conducted to compare the microbiological properties of chickens labelled free-range (according to the EC Directive 1538/91) if compared with conventional ones. Free range chickens belonging to medium growing Isa strain were raised for 70 d with continuous daytime access to open-air area from 28 d to slaughter age and an indoors stocking density not exceeding 27.5 kg/sqm. Conventional chickens belonged to a fast growing hybrid (Ross 708) and were raised for 50 d under intensive conditions. During slaughtering, 20 birds per each group before and after plucking, after evisceration and refrigeration (i.e. 5 birds per each step) were randomly collected and used for the quantitative evaluation (i.e. Log CFU/carcass) of total aerobic bacteria, Enterobacteriaceae and Campylobacter. Moreover, the detection of Salmonella was performed on 5 refrigerated carcasses per group as well as on their intestines (also Campylobacter was assessed) and neck skin of 10 additional birds. All microbiological determinations were performed using ISO based methods. Moreover Salmonella was further detected and Campylobacter quantified using traditional and RT-PCR, respectively. The total aerobic and Campylobacter counts before (i.e. 7.88 vs 8.39 and 6.05 vs 7.04 Log CFU/carcass) and after (i.e. 7.29 vs 7.75 and 5.09 vs 6.31 Log CFU/carcass) plucking were significantly lower in free range than conventional birds. The Enterobacteriaceae count showed the same trend but only after plucking (i.e. 6.42 vs 7.03 Log CFU/carcass). In both conventional and free range systems, positive Salmonella neck skin samples collected before refrigeration were obtained (i.e. 2/5 vs 3/5). However, all carcasses tested after refrigeration but one, belonging to conventional birds, turned out as negative.