The aim of the study was to determine the influence of the maintenance system of laying hens on the bacterial pollution of the egg shell surfaces of consumer eggs. Eggs derived from four acceptable maintenance systems of hens were selected for the investigations: caged, litter, free ranging, ecological, whose source was from the Lublin voivodeship and obtained during the spring and summer period (April – July). 200 eggs were examined, 50 from each of the examined maintenance systems. All the examined eggs belonged to the L weight class. The egg surface was calculated using Pagannelli et. al.’s formula: Ps = 4.835 × M⁰·⁶⁶². Next the egg was rinsed with a sterile liquid, attaining a 10⁻¹/cm² thinner egg shell surface, which was again thinned down by a tenth. In the examined material the following were determined: the general oxygen bacteria count, the number of proteolitic and psychrophilic bacteria, bacteria from the Enterobacteriaceae family, as well as micro-organisms of the Enterococcus and Staphylococcus type. The measurements were conducted according to Polish norms. The bacteria count (the units forming a colony) was presented in a decimal logarithmic form, and subsequently expressed as log jtk/cm² of an egg shell. It has been confirmed that the total number of oxygen bacteria on the eggs was: from caged hens log 4.95 jtk/cm²; litter, log 5.35 jtk/cm²; free ranging, log 5.25 jtk/cm²; while from ecologically sustained hens, log 5.18 jtk/cm². The pollution on eggs from the caged maintenance system was significantly lower than those from the litter system. The proteolitic bacteria count on eggs from the maintenance systems was log 4.19 from the caged, log 4.71 from litter, log 4.72 from free ranging, and log 4.54 jtk/cm² from the ecological. Significant differences in pollution were confirmed in this type of bacteria between the caged and litter as well as free ranging maintenance systems. The psychrophilic bacteria pollution ranged from log 3.66 jtk/cm² of an egg shell in the caged system to log 4.02 jtk/cm² in the litter system. Significant differences in pollution in this type of bacteria occurred only between the caged and litter systems. The bacteria count of the Enterobacteriaceae family ranged from log 0.65 jtk/cm² on eggs derived from the litter system to log 1.64 jtk/cm² from hens kept in the free ranging maintenance system. Significant differences in pollution were determined in this type of bacteria between the litter, free ranging and both of the remaining examined maintenance systems. The bacteria count of the Enterococcus type in the case of the caged system was log 1.08, litter log 3.10, free ranging log 2.34 and log 2.08 jtk/cm² from the ecological maintenance system. Significant differences in bacteria of the Enterococcus type were determined between the caged and litter systems, and both of the remaining examined maintenance systems, which did not differ among themselves. In the case of the bacteria of the Staphylococcus type, the lowest pollution was determined on the egg shells derived from the caged system – log 2.73 jtk/cm², while the greatest in the free ranging (log 4.36) and litter (log 4.58 jtk/cm²) systems. It was confirmed that the maintenance system of laying hens has a significant influence on bacterial pollution of the consumer egg shells. The highest hygienic quality was demonstrated by eggs from the caged system, the lowest from the litter and free ranging systems.
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