Tyson Cuts Earnings Forecast, Shares Fall  CHICAGO (Reuters) - Tyson Foods Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=TSN.N target=/stocks/quickinfo/fullquote"&gt;TSN.N&lt;/A&gt; on Monday cut  its earnings forecast after making a wrong bet on the direction  of grain prices and demand for chicken and beef proved weaker  than expected, sending its shares down 8 percent.