Changes in microbial ecology during poultry production

[摘要] Microorganisms, especially pathogens, play an important role in the deteriorationof poultry meat and its products causing spoilage or food poisoning. The meatrenders an ideal medium for the growth and progression of microorganismsoriginating from the environment on the farm (eggs and broiler), transport to theabattoir as well as the abattoir. As far as we know, no attempts were undertakento determine the total microbial spectrum, including bacterial and yeastpopulations from the egg unto the chicken carcass after slaughtering. A historicalreview of the incidence and extent of microorganisms associated with poultryand it's environment is given in Chapter 1. The background of poultryproduction and contribution of microorganisms (for example pathogens andyeasts) are highlighted. In Chapter 2 a survey was undertaken to determine the incidence, extent andserotypes of different pathogens on and in freshly laid eggs as well as incubatedeggs in the breeder broiler hatchery. In addition, the number of viable cells ofbacteria and yeasts were also determined. Microbial counts on the dirty eggspredominated. A major decline in microbial numbers on the egg shells, however,were observed after 18 days in the incubator. The deduction in bacterialpopulations present on the egg shells after 18 days in the incubator, is ascribed tothe constant fogging of the environment inside the incubator with clinafarm. Theirregular gathering of eggs as well as the dirty hands of the egg collectors couldhave been the major contributors of the high counts on these eggs. The onlypathogens obtained were Listeria and E. coli type 1.In Chapter 3 the microbial populations associated with the caecum and liver ofbroilers as well as with the environment were determined. Anaerobic plate countsreflecting the dominance of bacterial populations were constantly the highestascribed to the contents of the gut. Salmonella, Staphylococcus aureus and E. colitype 1 were isolated from the caecum, however no Listeria were isolated.Salmonella and E. coli type 1 were isolated from the liver. The high incidence ofpathogens associated with the broilers is an indication of the pathogens that enterthe abattoir. These levels of pathogens, further increased during transport to theabattoir.In Chapter 4 the incidence and extent of microbial populations associated withbroiler meat and the environment in the abattoir were evaluated. All thepathogens present on the farm were also observed in the abattoir. The mainreasons for the similarity in the incidence of pathogens on the farm and theabattoir were ascribed to the transport from the farm to the abattoir, the processof slaughtering, equipment surfaces in the abattoir and people handling the meat.Aerobic plate counts predominated on the neckskin samples, equipment surfacesas well as in the water and air of the abattoir. E. coli type 1 clearly predominatedon the neckskin samples as well as on the equipment surfaces, followed byStaphylococcus (U/reus and that by Salmonella. No Listeria isolates was,however, isolated from either the broiler farm or the abattoir, but was indeedobserved on the egg shells from the breeder farm. Although a pattern reflecting the incidence of pathogens could be establishbetween the broiler farm and the abattoir, no comparison could be made with theeggs from the breeder farm and hatchery. This may be blamed on the sampling ofinsufficient number of eggs, or the lack of multiple repetitions. Despite theinability to detect the primary sources of pathogens the distinct possibilityremained that the broiler farm was the main contributor towards microbialcontamination and infection. Therefore, more effort is needed to control the diseases and infections on broilerfarms, because in an abattoir you only get out what you put in.

[发布机构] University of the Free State