While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Sanderson Farms (NASDAQ:SAFM) sank 3% today after Stephens downgraded the poultry producer from overweight to equal weight.

So what: Along with the downgrade, analyst Farha Aslam lowered her price target to $65 (from $81), representing just 4% worth of upside to Friday's close. While contrarian investors might be attracted to the stock's steady slide since early August, Stephens thinks that falling chicken prices will likely weigh much more heavily on Sanderson's results than Wall Street expects.

Now what: Stephens sees Sanderson earning $6.22 per share in 2014 and expects the stock to trade at 10-11 times that estimate. "While feed costs, particularly corn prices, are declining -- in line with our expectations, chicken pricing is declining much faster than we had predicted as demand has been mixed and supply has been heavy," cautioned Stephens. "We are not looking for the chicken industry or Sanderson Farms to post negative earnings, but do anticipate that results will fall significantly short of consensus expectations." Of course, with the stock now off about 20% from its 52-week highs and trading at a price-to-sales of 0.55, those short-term concerns might provide patient investors with a solid long-term value opportunity.