Tyson Foods Reports Lower Earnings  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;, the nation's  largest meat producer, on Monday reported a sharp drop in  quarterly earnings due in part to poor results in its beef  segment.