Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of dairy supplier Dean Foods (NYSE:DF) jumped as much as 15% today, after announcing it would spin off its WhiteWave-Alpro Unit.

So what: The IPO is expected to bring in about $300 million, as Dean said it would sell 20 million shares priced between $14 and $16. With a market cap near $3 billion, that cash infusion accounts for the full gain in the share price. Dean Foods would still be the majority shareholder in WhiteWave, and both companies have said they would use the proceeds to pay down a heavy debt burden. Dean Foods had $3.5 billion on the books as of its last report.

Now what: Dean had already announced the spinoff of WhiteWave, the parent of Silk soy milk and Horizon organic dairy products -- only the pricing was news. The market often cheers spinoffs as a sign of "unlocking value," but Dean is also losing direct ownership of a fast-growing segment here. The company said it predicts WhiteWave operating income to grow by 22% this quarter to $64 million. By comparison, net income last quarter for the whole company was only $146 million. Considering WhiteWave's significant contribution to the bottom line, this rally seems overdone.

Make sure you know what's cooking with Dean Foods? Add the company to your watchlist here.

Fool contributor Jeremy Bowman has no positions in the stocks mentioned above. The Motley Fool owns shares of Dean Foods Company. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.