The Effect of Housing Environment on Commercial Brown Egg Layer Production, USDA Grade and USDA Size Distribution.

Consumer demand for retail cage-free eggs is driving the layer industry towards greater use of extensive housing environments. However, there is limited research on how these environments affect egg production characteristics of brown egg layers, as was the focus of this study. Five housing environments were evaluated under typical industry conditions, including conventional cages, enrichable colony cages, enriched colony cages, cage-free and free-range. Three different brown egg laying strains were housed in the different housing environments and managed according to standard husbandry practices and stocking densities. Data collection for the strains began at 17 weeks of age, with a base period of 28 days for feed weigh backs and egg quality assessments. Housing environment had a highly significant (p < 0.0001) effect on all egg production characteristics measured, including egg production rates (% hen-day and % hen-housed), feed consumption (g/bird/day), feed conversion (egg g/feed g), and mortality rate (%) as well as percent grade A, B, and loss. Previous research revealed better egg production metrics for white egg layers in caged environments than extensive environments. In contrast, we observed brown egg layers had optimum production results for the free-range housing environments, and the poorest performance in enrichable colony cages.

Evaluation of Physical Egg Quality Parameters of Commercial Brown Laying Hens Housed in Five Production Systems.

This study evaluates the effect of housing environment on the egg quality characteristics of brown egg layers as many different environments are currently used in the industry. Battery cages, barren colony cages, enriched colony cages, cage-free, and free-range environments were evaluated. Overall, all egg quality measurements were affected by housing environment (p < 0.01) except for vitelline membrane strength, elasticity, and egg solids. Eggshells and yolks were lightest in barren colony cages and darkest from free-range hens (p < 0.0001). Free-range eggs were heavier than eggs from all other environments (p < 0.0001). Cage-free eggs had lower albumen height and Haugh units than other environments (p < 0.0001). Lastly, cage-free and free-range eggs had stronger eggshells than the other environments (p < 0.0001), and free-range eggs had more elastic eggshells than eggs from conventional battery cages and barren colony cages (p < 0.01). Access to the range seemed to give free-range hens different nutritional advantages, which allowed for the darker yolks and shells. Furthermore, eggs from barren colony cages seemed to exhibit more negative characteristics. Simply adding enrichments to colony cages did not improve or detract from egg quality. From this research, it appears that, as the industry moves toward extensive environments, the egg quality of brown egg layers will improve.

Effects of full-fat high-oleic soybean meal in layer diets on nutrient digestibility and egg quality parameters of a white laying hen strain.

This study was conducted to understand the impact of including full fat high-oleic soybean meal in layer hen diets on nutrient digestibility and added nutritional value in eggs. Forty-eight layers (∼36 wk old) were randomly assigned to one of 4 isonitrogenous (18.5% crude protein) treatment diets with 12 replicate birds per treatment in a 3-wk study. Treatments were 1) solvent extracted defatted soybean meal + corn diet, 2) dry extruded defatted soybean meal + corn, 3) full-fat soybean meal + corn, 4) high-oleic full-fat soybean meal + corn diet. Apparent ileal digestibility of crude fat (CF) and crude protein (CP) were determined using celite (∼2%) as an indigestible marker. Tibia strength and egg quality parameters (egg weight, shell strength, Haugh unit, shell color, and yolk color) were recorded during the study. Fatty acid profiles, including the monounsaturated fatty acid, oleic acid (C18:1, cis), in eggs and adipogenic tissue (liver, muscle, and fat pad) were measured using gas chromatography (GC-FID). Digestibility values of CF ranged from 71 to 84% and CP varied from 67 to 72% for treatment diets, with treatment mean values being no different (P > 0.05) between treatment diets. No differences between treatment diets in tibia strength or egg quality parameters (egg weight, shell strength, and Haugh unit) were observed (P > 0.05) except for yolk color. Similarly, there were no differences in the total lipids in egg yolk (P > 0.05) between treatment diets. However, oleic acid percentage of total lipid in egg and tissue was significantly higher (P < 0.001) in hens given the high-oleic full-fat soybean meal diet than in other treatment groups. No difference was observed in oleic acid percentage of total lipid in egg between the other 3 treatment diets (P > 0.05). Overall, the results exhibited that the eggs and tissue of layer hens fed the full-fat high-oleic acid soybean meal diet were higher in oleic acid while the CF and CP digestibility remained similar to the digestibility of the other diets.

High-Containment Agriculture Animal Research: An AAALAC International Perspective.

Institutions that conduct high-containment agricultural research involving domestic livestock represent a specialized category of programs that are accredited by AAALAC International. The accreditation process includes a comprehensive assessment of the overall program of animal care and use. However, the complex design of these facilities and the unique care required for animals in this type of environment often mean that additional attention will be directed at areas regarded as higher risk when the programs are evaluated. Specific issues that may stimulate additional discussion and interest include animal housing practices, environmental conditions inside the facility, maintenance of procedure and support areas, methods for obtaining and safely transporting healthy research animals, strategies to minimize animal pain and distress, unusual protocol review challenges, and institutional policies relevant to personnel training and safety. These issues are further discussed to inform institutions of potential concerns that should be reviewed and assessed during internal preparations for accreditation visits by AAALAC site visit teams.

Research Note: Contamination of eggs by Salmonella Enteritidis and Salmonella Typhimurium in experimentally infected laying hens in indoor cage-free housing.

Contaminated eggs are a leading source of human Salmonella infections and this problem continues to challenge public health authorities and egg industries around the world. Salmonella invasion of the ovaries and oviducts of infected laying hens can result in bacterial deposition inside the edible portions of developing eggs. The introduction, persistence, and transmission of salmonellae in commercial egg-laying flocks are influenced by flock management practices, but the food safety ramifications of different types of laying hen housing remain unresolved. The present study assessed the frequency of internal contamination of eggs after experimental Salmonella Enteritidis and S. Typhimurium infection of laying hens in indoor cage-free housing. Groups of 72 hens were housed on wood shavings in isolation rooms simulating commercial cage-free barns with community kick-out nest boxes and perches and 1/3 of the hens in each room were orally inoculated with 8.0 × 107 cfu of 2-strain mixtures of either S. Enteritidis (2 rooms) or S. Typhimurium (2 rooms), and the entire internal contents of all eggs laid 5 to 30 d postinoculation in nest boxes or on the flooring substrate were cultured to detect Salmonella. Contaminated eggs were laid between 8 and 28 d postinoculation. The overall incidence of S. Enteritidis isolation from eggs (3.41%) was significantly (P = 0.0005) greater than S. Typhimurium (1.19%). The contamination frequencies associated with the 2 egg collection locations were not significantly different (P > 0.05). These results demonstrate that oral infection of a relatively small proportion of laying hens in indoor cage-free housing with invasive Salmonella serovars can result in the production of internally contaminated eggs at low frequencies over a period of nearly a month postinoculation.

The effects of high-oleic peanuts as an alternate feed ingredient on performance, ileal digestibility, apparent metabolizable energy, and histology of the small intestine in laying hens.

We aimed to determine the effects of feeding a high-oleic peanut (HOPN) diet to egg-producing laying hens on egg quality, digestibility, and feed conversion. Three isonitrogenous and isocaloric dietary treatments were formulated with 1) Control diet (CON)-a corn-soybean meal conventional diet with 7.8 % added poultry fat, 2) HOPN diet-dietary inclusion of ~20% coarse-ground whole HOPN, and 3) oleic acid (CON-OA) diet-a control diet supplemented with 2.6% oleic fatty acid oil. Ninety-nine 57-wk-old brown Leghorn laying hens were randomly assigned to 33 animals per treatment. Animals were housed individually for 8 wk. Body and feed weights were recorded weekly and feed conversation ratio was calculated. Bi-weekly, shell eggs were analyzed for quality (yolk color, albumen height, and Haugh unit [HU]). Jejunum samples were collected at week 8 for histomorphometric analysis. Analysis of variance was performed on all variables using a general linear mixed model. Laying hens fed the CON-OA diet produced greater number of eggs relative to those fed the HOPN and control diets (P < 0.05). The roche yolk color value was higher (P < 0.001) in eggs from hens fed the HOPN diet. There were no differences in laying hen performance, eggshell color, eggshell strength, eggshell elasticity and egg albumen height, or egg HU, ileal fat digestibility, or villi surface among treatment groups. However, the apparent metabolizable energy (P < 0.01) and ileal protein digestibility (P = 0.02) were greater in laying hens fed the HOPN diet relative to the CON diet. This study suggests that whole unblanched high-oleic peanuts may be an acceptable alternative feed ingredient for laying hens.

Research Note: Horizontal transmission and internal organ colonization by Salmonella Enteritidis and Salmonella Kentucky in experimentally infected laying hens in indoor cage-free housing.

The transmission of Salmonella to humans via contaminated eggs is an international public health concern. S. Enteritidis is deposited inside eggs after colonizing reproductive tissues of infected hens. Diverse housing facility characteristics and flock management practices influence Salmonella persistence and transmission in poultry, but the food safety consequences of different housing systems for laying hens remain unresolved. The present study compared the horizontal transmission of infection and invasion of internal organs during the first 2 wk after experimental S. Enteritidis and S. Kentucky infection of laying hens in indoor cage-free housing. Groups of 72 hens were housed in isolation rooms simulating commercial cage-free barns, and 1/3 of the hens in each room were orally inoculated with either S. Enteritidis (2 rooms) or S. Kentucky (2 rooms). At 6 d and 12 d postinoculation, 12 inoculated and 24 contact-exposed hens in each room were euthanized, and samples of liver, spleen, ovary, oviduct, and intestinal tract were removed for bacteriologic culturing. All orally inoculated hens were positive for intestinal colonization by S. Enteritidis at 6 d postinfection, and 70.8% of contact-exposed hens had become colonized by 12 d. S. Enteritidis was isolated from 100% of livers and 50.0% of ovaries from inoculated birds at 6 d and from 41.7% of livers and 10.4% of ovaries from contact-exposed birds at 12 d. The majority of both orally inoculated and contact-exposed hens were positive for intestinal colonization by S. Kentucky at 6 d, but S. Kentucky was found in other internal organs of both inoculated and contact-exposed hens significantly (P < 0.05) less often than S. Enteritidis at both sampling intervals. These results indicate that Salmonella infection can spread rapidly and extensively among hens in cage-free indoor housing, including a high frequency of internal organ involvement for invasive S. Enteritidis.

Pooling of Laying Hen Environmental Swabs and Efficacy of Salmonella Detection.

ABSTRACT: Environmental testing for Salmonella Enteritidis is required for U.S. shell egg producers with ≥3,000 hens on a farm. The egg producer assumes all costs for the mandatory testing. According to the U.S. Food and Drug Administration (FDA) Egg Rule, either manure scraper or drag swabs can be collected according to published guidelines and requirements. The present study was undertaken to determine the efficacy of Salmonella detection with one-, two-, and four-swab pools of either manure scraper or drag swabs. Resistant isolates of Salmonella serovars Enteritidis (1,000 ppm of streptomycin), Heidelberg (200 ppm of nalidixic acid [NA]), Typhimurium (200 ppm of NA), and Kentucky (200 ppm of NA) were utilized. Low (approximately 8.4 CFU) and high (approximately 84 CFU) levels of inocula were introduced onto a single swab within a pool. Single flocks from each conventional cage (manure scraper swabs) and cage-free barn (drag swabs) were monitored throughout the study at the ages required under the FDA Egg Rule. The highest and most consistent recovery of inoculum was found in single swab samples. For low dose inocula, recovery of isolates was low from single manure scraper swabs (57.9 to 29.2%) and decreased as more swabs were added to the pool. Recovery of isolates from manure scraper swabs was higher for high dose inocula, although Salmonella Heidelberg was outcompeted by the naturally occurring flora and had the lowest rate of recovery among the isolates tested. One- and two-swab pools of drag swabs had similar rates of recovery at both low and high doses for Salmonella Enteritidis, Salmonella Heidelberg, and Salmonella Typhimurium. When Salmonella Enteritidis and Salmonella Kentucky were combined in an inoculum, Salmonella Enteritidis was recovered at a much higher rate than was Salmonella Kentucky for all types of swabs and doses of inocula. Pooling of two drag swabs allowed for similar detection of low and high dose Salmonella, but the pooling of manure scraper swabs decreased detection of low dose Salmonella.

Potential Transfer of Peanut and/or Soy Proteins from Poultry Feed to the Meat and/or Eggs Produced.

Previous studies have demonstrated that allergenic feed proteins from peanuts in the diets of layer hens are not detected in the eggs produced. Hence, in this study, we aimed to determine if soy and/or peanut proteins in poultry feed rations of broiler chickens or layer hens would be transferred or detectable in the meat or eggs produced. To meet this objective, 99 layer hens and 300 broiler chickens were equally divided into treatment groups and fed one of three experimental diets: control soybean meal and corn diet, whole unblanched high-oleic peanut and corn diet (HO PN), or a control diet spiked supplemented with oleic acid (OA) oil. At termination, broiler chickens were processed, and chicken breast samples of the left pectoralis muscle were collected, and eggs were collected from layers. Total protein extracts from pooled egg samples and chicken breast samples were subjected to enzyme-linked immunosorbent assay (ELISA) methods and immunoblotting analysis with rabbit antipeanut agglutinin antibodies and rabbit antisoy antibodies for the detection of peanut and soy proteins. Peanut and soy proteins were undetected in all pooled egg samples and individual chicken breast meat samples using immunoblotting techniques with rabbit antipeanut agglutinin and rabbit antisoy antibodies. Moreover, quantitative ELISA allergen detection methods determined all pooled egg samples and individual meat samples as "not containing" peanut or soy allergens. Therefore, this study helps to evaluate the risk associated with the potential transfer of allergenic proteins from animal feed to the products produced for human consumption.

Contamination of eggs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing.

Human illness caused by the consumption of eggs contaminated with Salmonella Enteritidis is a continuing international public health concern. This pathogen is deposited inside the edible contents of eggs as a consequence of its ability to colonize reproductive tissues in infected hens. Conditions in the housing environment can influence the persistence and transmission of avian Salmonella infections, but the food safety ramifications of different poultry management systems are not entirely clear. The present study assessed the deposition of S. Enteritidis inside eggs laid by groups of experimentally infected laying hens of 4 commercial genetic lines (designated as white egg lines W1 and W2 and brown egg lines B1 and B2). Groups of hens from each line were housed at 555 cm2 of floor space per bird in both conventional cages and colony units enriched with access to perches and nesting areas. All hens were orally inoculated with 5.75 × 107 cfu of a 2-strain S. Enteritidis mixture, and the internal contents of eggs laid 5 to 24 D post-inoculation were cultured to detect the pathogen. No significant differences in egg contamination frequencies were found between the 2 housing systems for any of the hen lines. Contaminated eggs were laid between 7 and 21 D post-inoculation at an overall frequency of 2.47%, ranging from 0.25 to 4.38% for the 4 hen lines. The frequency of S. Enteritidis recovery from egg samples was significantly (P < 0.05) lower for line B2 than for any of the other lines, and the egg contamination frequency for line W1 was significantly greater than for line W2. The overall incidence of contamination among white eggs (3.38%) was significantly higher than among brown eggs (1.56%). These results demonstrate that S. Enteritidis deposition inside eggs can vary between genetic lines of infected laying hens, but housing these hens in 2 different systems did not affect the production of contaminated eggs.

Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens of four commercial genetic lines in conventional cages and enriched colony housing.

The prevalence of Salmonella Enteritidis in commercial egg-laying flocks is a prominent public health concern because contaminated eggs cause human illness. Deposition of this pathogen inside eggs results from bacterial colonization of reproductive tissues in infected hens. Environmental conditions can influence avian Salmonella infections, but the food safety consequences of different poultry housing systems remain uncertain. The present study assessed the invasion of internal organs by Salmonella Enteritidis in groups of experimentally infected laying hens of four commercial genetic lines (designated as white egg lines W1 and W2 and brown egg lines B1 and B2). Groups of hens from each line were housed at 555 cm2 of floor space per bird in both conventional cages and colony units enriched with access to perches and nesting areas. All hens were orally inoculated with 5.75 × 107 colony-forming units of a two-strain Salmonella Enteritidis mixture. At 6 to 7 d post-inoculation, hens were euthanized, and samples of liver, spleen, ovary, oviduct, and intestinal tract were removed for bacteriologic culturing. The frequency of Salmonella Enteritidis recovery from intestinal samples was significantly (P < 0.05) greater for the two white egg lines combined than for the two brown egg lines combined in both conventional cage (72.2% vs. 50.0%) and enriched colony housing systems (66.7% vs. 37.5%). The frequency of intestinal Salmonella Enteritidis isolation from line B1 was significantly higher from hens in conventional cages (47.2%) than in enriched colonies (22.2%), but no differences were observed for other hen lines. Line W1 yielded more positive intestinal samples than either brown egg line in conventional cages, and line B2 had fewer positive intestinal samples than all other lines in enriched colonies. There were no significant differences between hen lines or housing systems in Salmonella Enteritidis isolation from other internal organs. These results demonstrate that Salmonella Enteritidis colonization of the intestinal tract can vary between genetic lines of egg-laying hens and that some lines are subject to housing system influences on Salmonella susceptibility.

Feeding high-oleic peanuts to layer hens enhances egg yolk color and oleic fatty acid content in shell eggs.

Previous studies have identified normal-oleic peanuts as a suitable and economical broiler feed ingredient. However, no studies to date have examined the use of high-oleic (HO) peanut cultivars as a feed ingredient for laying hens and determined the impact of feeding HO peanuts on performance and egg nutritive qualities. This project aimed to examine the use of HO peanuts as a feed ingredient for layer hens to determine the effect on performance, egg lipid chemistry, and quality of the eggs produced. Forty-eight 40-wk-old layer hens were fed a conventional soybean meal + corn control diet or a HO peanut + corn diet for 10 wk in conventional battery cages. Body and feed weights were collected weekly. Pooled egg samples were analyzed for quality, lipid analysis, and peanut protein allergenicity. There were no significant differences in hen performance or egg quality as measured by USDA grade quality, egg albumen height, or egg Haugh unit between the treatment groups. However, eggs produced from layer hens fed the HO peanut + corn diet had reduced egg weights relative to the controls (P = 0.0001). Eggs produced from layer hens fed the HO peanut diet had greater yolk color scores (P < 0.0001), HO fatty acid (P < 0.0001), and ß-carotene (P < 0.0001) levels in comparison to the controls. Eggs produced from hens fed the control diet had greater palmitic and stearic saturated fatty acids (P < 0.0001), and trans fat (P < 0.0001) content compared to eggs produced from hens fed the HO peanut diet. All egg protein extracts from all treatments at each time point were non-reactive with rabbit anti-peanut agglutinin antibodies. This study identifies HO peanuts as an abundant commodity that could be used to support local agricultural markets of peanuts and poultry within the southeastern United States and be of economic advantage to producers while providing a potential health benefit to the consumer with improved egg nutrition.

Mineral content of eggs differs with hen strain, age, and rearing environment.

Egg nutrient quality is strongly influenced by hen diet but is also affected by rearing environment, hen strain, and hen age. The objective of the current study was to determine the effect of: 1) conventional battery cages, 2) enrichable cage systems, 3) enriched colony housing, 4) cage-free, and 5) free-range rearing systems on mineral concentrations of whole, dried egg (yolk and albumen combined) from TA Tetra White (TW) and Hy-Line Brown (HB) hens at 44, 68, and 88 wk of age. We hypothesized that mineral concentration of eggs would differ among rearing systems but not between strains or with hen age. Hens held in enriched colony housing systems produced eggs with 10% lower Mg and 11% lower Mn levels than conventional hens. Concentrations of Ca and Cu were higher (7 and 8%, respectively) in eggs from TW hens than from HB hens. Eggs from HB hens had 8% higher concentrations of Fe, 6% higher Mg and 5% higher Mn than TW hens. Mn was higher in eggs from 44-wk hens than from 68- or 88-wk hens (16 and 11%, respectively). Interaction effects between rearing environment and hen age were observed for K and Mn concentrations. Eggs from 68-wk hens in conventional rearing systems contained 14 to 21% more K than eggs from conventional hens at 44- and 88 wk and 14 to 18% more than eggs from 68-wk hens in other rearing systems. At 88 wk of age, hens in conventional rearing systems produced eggs with higher Mn concentration than hens in enrichable or enriched colony housing systems (22 and 23%, respectively). Interactions between rearing environment, hen strain, and hen age were observed for egg Zn levels among 44- and 68-wk hens but were not detectable among 88-wk hens regardless of rearing system or hen strain. Observed differences in egg mineral content in our study were small and are unlikely to have substantial impact on human nutrition.

A novel non-invasive method for evaluating electroencephalograms on laying hens.

The use of electroencephalograms (EEG) to study the avian brain relative to behavior was conducted as early as the 1960's. EEG readings, combined with visual cues, provide the ability to elucidate and correlate behaviors to neurological and physiological changes in a chicken. The use of EEG recordings in animal models require access to the brain to implant electrodes. Having the ability to observe EEG activity on sensible birds without surgical implantation could broaden the research in this area and give further insight related to the hen's state of awareness. The development, construction, and implementation of a minimally invasive EEG electrode placement method is described. After implementation, test animals were exposed to extreme environmental stressors as part of a concurrent depopulation methods study and EEG placement withstood the condition changes and corresponding animal physical activity. Sixteen white commercial laying hens had three monopolar 32-gauge needle electrodes inserted subcutaneously and secured to their head and body. Electrodes were attached to a pre-amplifier which transferred EEG signals to a laptop based recording system. Once the electrodes were in place, the hens were placed in individual treatment/observation chamber then various environmental stressors were applied. Verification that the observed brainwave activity was neural and not muscular was done using a photic stimulation validation test. Behavior observations were recorded to correlate sensible and insensible brainwave activity. The validation test and behavior observations demonstrated the method was successful in measuring EEG in sensible laying hens. The use of a non-surgical method for recording EEG will broaden research capabilities and enhance the understanding of a hen's response its environment, eliminate the need for invasive surgical procedures, and minimizes the confounding components of anesthesia, brain surgery, and recovery. With further refinements, the method could open new avenues in avian behavioral and physiological research.

Frequency and Duration of Fecal Shedding of Salmonella Serovars Heidelberg and Typhimurium by Experimentally Infected Laying Hens Housed in Enriched Colony Cages at Different Stocking Densities.

Eggs contaminated with Salmonella Enteritidis are leading sources of human salmonellosis, but Salmonella Heidelberg and Salmonella Typhimurium are also egg-associated pathogens. The management practices and housing facilities characterizing different systems for housing commercial egg flocks can influence Salmonella persistence and transmission. Animal welfare aspects of poultry housing have been widely debated, but their food safety ramifications are not thoroughly understood. The present study assessed the effects of two different bird stocking densities on the frequency and duration of fecal shedding of strains of Salmonella Heidelberg and Salmonella Typhimurium in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. In separate trials, laying hens were distributed into two groups housed in enriched colony cages at stocking densities of 648 and 973 cm2/bird, and a third group was housed in conventional cages at 648 cm2/bird. All hens were orally inoculated with doses of 108 colony-forming units (CFU) of either Salmonella Heidelberg or Salmonella Typhimurium. At eight weekly postinoculation intervals, samples of voided feces were collected from beneath each cage and cultured to detect Salmonella. Fecal shedding of Salmonella Heidelberg continued for 8 wk in all housing groups, but Salmonella Typhimurium shedding ceased after as little as 5 wk in enriched colony cages at low stocking density. After Salmonella Heidelberg infection, the overall frequency of positive fecal cultures for all sampling dates combined was significantly (P < 0.05) greater from either conventional cages (51.0%) or enriched colony cages (46.5%) at high stocking density than from enriched colony cages at low stocking density (33.3%). No significant differences in Salmonella Typhimurium fecal isolation were identified between housing groups. These results demonstrate that stocking density can affect intestinal colonization and fecal shedding in laying hens for some (but not necessarily all) Salmonella serovars or strains.

Frequency and Duration of Fecal Shedding of Salmonella Enteritidis by Experimentally Infected Laying Hens Housed in Enriched Colony Cages at Different Stocking Densities.

Human infections with Salmonella Enteritidis are often attributed to the consumption of contaminated eggs, so the prevalence of this pathogen in egg-laying poultry is an important public health risk factor. Numerous and complex environmental influences on Salmonella persistence and transmission are exerted by management practices and housing facilities used in commercial egg production. In recent years, the animal welfare implications of poultry housing systems have guided the development of alternatives to traditional cage-based housing, but their food safety consequences are not yet fully understood. The present study assessed the effects of different bird stocking densities on the frequency and duration of fecal shedding of S. Enteritidis in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. In two trials, groups of laying hens were distributed at two stocking densities (648 and 973 cm2/bird) into enriched colony cages and (along with a group housed in conventional cages at 648 cm2/bird) orally inoculated with doses of 1.0 × 108 cfu of S. Enteritidis. At 10 weekly postinoculation intervals, samples of voided feces were collected from beneath each cage and cultured to detect S. Enteritidis. Fecal shedding of S. Enteritidis was detected for up to 10 weeks postinoculation by hens in all three housing treatment groups. The overall frequency of positive fecal cultures was significantly (P < 0.05) greater from conventional cages than from enriched colony cages (at the lower stocking density) for the total of all sampling dates (45.0 vs. 33.3%) and also for samples collected at 4-9 weeks postinfection. Likewise, the frequency of S. Enteritidis isolation from feces from conventional cages was significantly greater than from enriched colony cages (at the higher hen stocking density) for the sum of all samples (45.0 vs. 36.7%) and at 6 weeks postinoculation. Moreover, the frequency of S. Enteritidis fecal recovery from enriched colony cages at the higher hen stocking was significantly greater than from similar cages at the lower stocking density for all 10 sampling dates combined (39.4 vs. 33.3%). These results suggest that stocking density can affect S. Enteritidis intestinal colonization and fecal shedding in laying hens, but some other difference between conventional and enriched colony cage systems appears to exert an additional influence.

Assessing the impact of egg sweating on Salmonella Enteritidis penetration into shell eggs.

Salmonella Enteritidis (SE) prevalence in eggs is a major concern to the egg industry. Some research has shown that egg sweating can increase Salmonella penetration into egg contents when refrigerated eggs are moved to a warmer temperature. This occurs when eggs are tempered before wash, to minimize thermal cracks. The effect of egg sweating on SE penetration into shell eggs over a 6 week storage period at 4°C was assessed. A 2 × 2 factorial of SE inoculation and egg sweating was utilized. Treatments included (SES) nalidixic acid (NA)-resistant SE inoculated and sweated, (SENS) NA-resistant SE inoculated and not sweated, (NSES) buffered peptone water (BPW) inoculated and sweated, and (NSENS) BPW inoculated and not sweated. Eggs were inoculated with 108 SE. Eggs formed condensation for approximately 17 min in a 32°C incubator. Shell rinse, shell emulsion, and egg contents were sampled then enumerated and assessed for prevalence of SE over a 6 wk storage period at 4°C. After wk 1, the SENS shell rinse had higher SE counts (0.32 log10 CFU/mL) than the other 3 treatments, where no SE was enumerated. A significant week by treatment interaction was found for the shell rinse SE detection (P < 0.05). In subsequent weeks, no SE counts were obtained from the egg shell rinse, shell emulsion, or egg contents. The SENS shell rinses had significantly higher SE prevalence than the SES rinses in weeks 1 (100% vs. 34.3%), 2 (57.6% vs. 22.2%), and 3 (38.2% vs. 11.1%) (P < 0.05). In samples from weeks 4, 5, and 6, there was no difference in SE prevalence between SES and SENS. Egg sweating did not increase SE penetration into the shell emulsion across treatment or week (P < 0.05). The decreasing trend of SE prevalence obtained over the study period indicate that refrigeration is effective at inhibiting SE growth. These results indicate that egg sweating occurring under common US egg handling practices is not harmful to egg safety.

Colonization of internal organs by Salmonella serovars Heidelberg and Typhimurium in experimentally infected laying hens housed in enriched colony cages at different stocking densities.

Contaminated eggs produced by infected commercial laying flocks are often implicated as sources of human infections with Salmonella Enteritidis, but Salmonella serovars Heidelberg and Typhimurium have also been associated with egg-transmitted illness. Contamination of the edible contents of eggs is a consequence of the colonization of reproductive tissues in systemically infected hens. In recent years, the animal welfare implications of diverse poultry housing and management systems have been vigorously debated, but the food safety significance of laying hen housing remains uncertain. The present study evaluated the effects of 2 different bird stocking densities on the invasion of internal organs by Salmonella serovars Heidelberg and Typhimurium in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. Laying hens were distributed at 2 different stocking densities (648 and 973 cm2/bird) into colony cages and (along with a group housed in conventional cages at 648 cm2/bird) orally inoculated with doses of 107 cfu of 2-strain cocktails of either Salmonella Heidelberg or Salmonella Typhimurium. At 5 to 6 d post-inoculation, hens were euthanized and samples of internal organs (cecum, liver, spleen, ovary, and oviduct) were removed for bacteriologic culturing. The overall frequency of Salmonella isolation from ceca after inoculation with strains of serovar Heidelberg (83.3%) was significantly (P < 0.001) greater than the corresponding value for strains of serovar Typhimurium (53.8%), whereas Salmonella was recovered significantly more often from both livers (85.2% vs. 53.7%; P < 0.0001) and spleens (78.7% vs. 56.5%; P = 0.0008) after inoculation with strains of serovar Typhimurium than strains of serovar Heidelberg. However, there were no significant differences (P > 0.05) between stocking densities or cage systems in the frequencies of isolation of either Salmonella serovar from any of the five sampled tissues. These results contrast with prior studies, which reported increased susceptibility to internal organ invasion by Salmonella Enteritidis among hens in conventional cages at higher stocking densities.

Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities.

Epidemiologic analyses have linked the frequency of human infections with Salmonella enterica subspecies enterica serovar Enteritidis to the consumption of contaminated eggs and thus to the prevalence of this pathogen in commercial egg-laying flocks. Contamination of the edible contents of eggs by Salmonella Enteritidis is a consequence of the colonization of reproductive tissues in systemically infected hens. The animal welfare implications of laying hen housing systems have been widely debated, but no definitive consensus has yet emerged about the food safety significance of poultry housing options. The present study sought to determine the effects of two different bird stocking densities on the invasion of internal organs by Salmonella Enteritidis in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. In two trials, groups of laying hens were distributed at two different stocking densities into colony cages and (along with a group housed in conventional cages) orally inoculated with doses of 1.0 × 10(7) cfu of Salmonella Enteritidis. At 5 to 6 d post-inoculation, hens were euthanized and samples of internal organs were removed for bacteriologic culturing. For both trials combined, Salmonella Enteritidis was recovered at a significantly (P < 0.05) greater frequency from hens in enriched colony cages at the higher stocking density than at the lower density from livers (75.0% vs. 51.4%) and ovaries (51.4% vs. 30.6%). However, spleens from hens in enriched colony cages at the higher stocking density were significantly less often positive for Salmonella Enteritidis than from hens in conventional cages at that same density (90.3% vs. 68.1%). These results suggest that stocking density can influence the susceptibility of hens to Salmonella Enteritidis, but other housing systems parameters may also contribute to the outcome of infections.

Persistence of fecal shedding of Salmonella Enteritidis by experimentally infected laying hens housed in conventional or enriched cages.

Salmonella Enteritidis can be deposited inside eggs laid by infected hens, so the prevalence of this pathogen in commercial egg-producing flocks is an important risk factor for human illness. Opportunities for the introduction, transmission, and persistence of salmonellae in poultry are potentially influenced by flock housing and management systems. Animal welfare concerns have spurred the development of alternatives to traditional cage-based housing. However, the consequences of poultry housing systems for food safety have not been fully resolved by prior research. The present study assessed the effects of two different housing systems (conventional cages and colony cages enriched with perching and nesting areas) on the persistence of fecal shedding of Salmonella Enteritidis by groups of experimentally infected laying hens. In each of two trials, 136 hens were distributed among cages of both housing systems and orally inoculated with doses of 10(8) cfu of Salmonella Enteritidis (phage type 13a in one trial and phage type 4 in the other). At weekly intervals, samples of voided feces were collected from beneath each cage and cultured to detect Salmonella Enteritidis. Fecal shedding of Salmonella Enteritidis was detected for up to 8 wk post-inoculation by hens housed in enriched colony cages and 10 wk by hens housed in conventional cages. For both trials combined, the frequency of positive fecal cultures was significantly (P < 0.05) greater for conventional cages than for enriched colony cages at 1 wk (84.7 vs. 71.5%), 2 wk (54.2 vs. 31.3%), 3 wk (21.5 vs. 7.6%), and 4 wk (9.7 vs. 2.8%) post-inoculation. These results demonstrate that the susceptibility of hens to intestinal colonization by Salmonella Enteritidis can differ between conventional and enriched cage-based production systems, although this effect does not necessarily translate into a corresponding difference in the longer-term persistence of fecal shedding.