Influence of housing system on bacterial eggshell contamination and horizontal transmission of Salmonella and Campylobacter among laying hens
Hannah, Jackie Fisher
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In the U.S. table egg industry, commercial laying hens are primarily housed in conventional battery cages. Although there are several advantages to cage management, this housing system has been extensively criticized for providing a barren and confined environment that physically restricts laying hens from performing many of their natural behaviors. To address growing hen welfare concerns associated with caged housing and to meet consumer demand for cage-free products, a number of table egg producers have transitioned to alternative, cage-free production systems. A study was conducted to evaluate eggshell bacterial numbers of non-washed and washed eggs from caged and cage-free laying hens housed on all wire slats or all shavings floor systems. Non-washed eggs produced in an all-shavings environment had higher aerobic plate counts (APC, 4.0 log10 cfu/mL of rinsate) than eggs produced on slats (3.6 log10 cfu/mL), which had higher bacterial counts than eggs produced in cages (3.1 log10 cfu/mL). Washing eggs significantly (P<0.05) reduced APC levels by 1.6 log10 cfu/mL. The influence of caged and cage-free housing systems on the spread of Salmonella and Campylobacter among laying hens was also evaluated. Hens challenged with Salmonella (S. Typhimurium or S. Enteritidis) and Campylobacter (C. coli or C. jejuni) were commingled with non-challenged hens in conventional cages, on all wire slats, or on all shavings floors. There was no significant difference (P<0.05) in horizontal transmission of Salmonella among non-challenged hens housed in cages (12%), on slats (15%), and on shavings (14%). However, horizontal transmission of Campylobacter among non-challenged hens was significantly lower in cages (28%) than on shavings (47%), with slats (36%) being intermediate. The objectives of the final study were to compare the colonization potential of the previously utilized S. Enteritidis marker strain to that of a S. Enteritidis field strain and the previously utilized S. Typhimurium marker strain, and evaluate the effects of a vancomycin pretreatment on Salmonella colonization in laying hens. The S. Enteritidis field strain and S. Typhimurium marker strain colonized the ceca, spleen, and liver/gallbladder at significantly (P<0.05) higher rates than the S. Enteritidis marker strain. Vancomycin pretreatment had no significant effect on Salmonella colonization.