White Leghorn hens will be housed in either conventional layer hen battery cages, in a quad- deck system with 10 layer hens/cage (403 cm2/bird) or housed free range housing with floor pens on litter with access to roosts or suitable free-range environment. FDA AHU assistance will not be required for this collaborative study. Piedmont Research Station, North Carolina Department of Agriculture and the Department of Poultry Science, North Carolina State University will provide experimental animals (White Leghorn Hens), experimental diets, housing and animal care over the 6 week experimental time frame. Also, all animal husbandry (feeding, providing water, maintenance of housing) will be provided by Piedmont Research Station, NC Dept. Agriculture, which will perform the collection and recording of weekly bodyweights. The experimental design consists of a 2 X 2 factorial experimental design with variables of feed grain size (fine versus coarse) in a mash diet and housing (conventional cages versus free-range) for 8 weeks (20 weeks to 28 weeks of age). The experimental diets will be formulated using least-cost linear programming to meet or exceed NRC (1994) nutrient requirements for layer hens. The corn included in the feed will be either ground fine or coarse for experimental dietary treatments. The corn in the finely ground mash diet will be ground in a hammermill equipped with a 3-mm screen with an average particle size of 560 yen?. Coarsely ground corn utilized in the alternative diet will be prepared by grinding using a 4-mm screen with subsequent sieving in a 60 in. separator using a 16-mm sieve with an average particle size greater than 3000 yen?. These dietary treatments will not contain antimicrobials or coccidiostats. Laying hens will be inspected daily and birds with visual health problems or poor body condition will be humanely euthanized by cervical dislocation and recorded for mortality rates. Eggs collected from production hens will be stored at 4??C for a maximum of 24 hours and subsequently, processed at the Department of Poultry Science, for analysis. At week 6, all hens will be euthanized by cervical dislocation performed by animal husbandry team at Piedmont Research Station, Salisbury NC and the following tissues will be aseptically collected: spleen, hen reproductive tract (ovaries and/or uterovaginal region) and cecum. These tissues will be stored in sterile ice cold buffered peptone water in stomacher bags and processed at the Department of Poultry Science, for analysis for microbial analysis for Salmonella. Additionally, environmental microbial analysis will be conducted on samples collected from each experimental housing type (conventional cage versus free range roost), drinking water and feed. Environmental testing will be conducted at the onsite of the experimentation, at week 3 of experiment, and at week 8 of experimentation (termination).
Health Relevance Statement A large number of laying hen egg producers are transitioning from conventional cages to either an enriched cage or free-range (non-cage) system, due to high demands and consumer attitudes toward natural and organic products;thus increasing the potential for bacterial contamination due to easier access and exposure to Salmonella transmitting vectors (birds, rodents, wild animals). Egg-associated illness due to Salmonella is a major public health concern, with table eggs being the primary source of Salmonella Enteritidis. Infected individuals may suffer gastrointestinal distress, short or chronic arthritis, and may lead to death, especially in vulnerable populations.