Poultry Producer's Stock Falls 23 Percent  NEW YORK (Reuters) - Poultry producer Sanderson Farms Inc.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=SAFM.O target=/stocks/quickinfo/fullquote"&gt;SAFM.O&lt;/A&gt; said on Tuesday its quarterly profit doubled on strong  demand, but warned of lower wholesale prices and higher grain  costs, sparking a 23 percent drop in its shares.