Common Sense in the Poultry Yard: A Story of Failures and Successes By J. P. Haig 1885 , page 123
http://tinyurl.com/lv9q2xj Parched or charred corn is. however, a very different matter. One of the best tonics for fowls, especially if they show a slight tendency either to constipation or diarrhoea, is charred corn. We have a large kettle,"which we bought for old iron because it was cracked, in which we occasionally parch corn for our chickens. The kettle was roughly "set" in brickwork by our man, and the chimney is simply two lengths of old stove pipe, the whole being out of doors. A wooden cover keeps rain and snow out of the pot. A Are of brush soon heats the kettle so that it will char corn. Haifa bushel is then poured in and constantly stirred until it is quite dark—partially burned, in fact. The chickens eat it greedily, and we feel certain that it does them good. Of course we feed but small quantities of it. Occasionally, however, we find chickens that will not touch it. In that case moisten it and roll it in "feed."
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Commercial Poultry, Volume 16 , No. 12 , Dec, 1907 Page 32
http://tinyurl.com/mpkyob5 " Charcoal is a heath promoter for the fowls. I you will put some extra ears of corn in a hot oven and let them burn quite black and feed whenthegrain gets cold enough you will perhaps be astonished to see how greedily the poultry will partake of the charred corn/ Give such a feed every 2 weeks. We do not mean that the fowls should have to depend on the charred grain for the meal, but an opportunity to eat what they want from the cob.". This exact article is also quoted in: American Poultry Advocate - Volume 31 1922 - Page 492 ====================
American Poultry Journal, Volume 45 no. 3 , March 1914 Page 463 ,
http://tinyurl.com/k6elx3c "Charred corn is excellent to feed to hens to increase their laying capacity. Char the corn on the cob throughly, taking care tnot to reduce any part of it to ashes.".
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999 Questions and Answers: A Guide to Success with Poultry,written and ... By Frank Heck 1903 , page 53
http://tinyurl.com/l6nfbkc Question—Is charred corn of any special value as a food? Answer—An occasional feed, say once a week, is very beneficial. Take shelled corn and burn it till well charred on the outside.
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The Poultry Monthly - Volume 15 1893 page 312
http://tinyurl.com/lz4rvng Both old and young chickens and fowls should be supplied with charcoal. It is an excellent tonic, and it is also of a fattening nature. Turkey raisers claim that they grow the best carcasses by its use, while those who raise broilers know that successful work cannot be done without the use of this article in the feed. For old fowls the best charcoal that can be used is charred corn on cob.
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The Poultry Herald Manual: A Guide to Successful Poultry Keeping 1898 - Page 134
http://tinyurl.com/kbcoubw CHARCOAL and salt
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Poultry Herald - Volumes 12-15 - June 1902 - Page 136
http://tinyurl.com/kkajxzl Charred corn or wheat will show its value in brighter combs and a more healthy appearance.