New York (CNN Business) Americans are splurging on food for their cats and dogs — but not snacks for them and their kids. That's not great news for General Mills.

General Mills GIS Shares of, the owner of Cheerios, Lucky Charms and Yoplait, fell 7% in early trading Wednesday after the company reported its latest quarterly results. That made General Mills the worst performing stock in the S&P 500.

Sales missed forecasts, despite soaring demand for the company's Blue Buffalo pet food.

The weaker-than-expected revenue was largely because of a 2% drop in sales in its North American retail unit, the division that includes Annie's branded cheddar bunnies, Chex, Fruit Snacks and the Fiber One and Nature Valley brands of bars.

General Mills said sales of other supermarket staples, such as cereal, yogurt and baked goods, held steady in the quarter. But that wasn't enough to offset the weakness in snacks.

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