"A spent hen is a laying hen past her prime laying age.She will still lay but not as often as the younger hens."
http://tinyurl.com/2wvd5uf

"Newsletters of a trade group representing egg producers regularly note the need to find new markets to "dispose" of spent hens. The primary options: pet food, compost — and schools, reports continue."
http://tinyurl.com/32hv5hl

"Preslaughter Mortality in Broiler Chickens, Turkeys, and Spent Hens Under Commercial Slaughtering

By M. Petracci, M. Bianchi, C. Cavani P. Gaspari,† and A. Lavazza - The incidence of dead on arrival (DOA) birds was surveyed over 33 broiler, 11 turkey, and 19 spent hen abattoirs representing the majority (around 70%) of the Italian poultry slaughter plants."
http://tinyurl.com/34r6vm3

http://tinyurl.com/34clt9z

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Note added at 10 days (2010-05-13 08:52:55 GMT) Post-grading
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My pleasure!