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- Tyson Foods shares sank to their lowest price in more than three years on Monday.
- The sell-off was sparked after the meatpacker unexpectedly swung to a second-quarter loss.
- Beef sales and volume fell in the quarter during a "challenging" period for meat sales.
Tyson Foods shares on Monday tumbled to a three-year low as a drop in beef sales contributed to pushing the company to a quarterly loss and lowering its outlook for revenue.