Investment stories that rely on growth through acquisition can be tricky. Adding debt to pay for those acquisitions ramps the risk even higher. But when it works, it can work extremely well.

Shareholders in VCA Antech (NASDAQ:WOOF) clearly hope that the company will continue to make prudent use of debt to acquire veterinary offices, further consolidating the highly fragmented pet-care industry.

So far, at least, it's still working. Revenue rose 23% in the quarter, split between more than 10% growth in the lab business (all organic) and greater than 26% growth in the animal hospital business. Given that same-store revenue in the hospital business was up 4.4%, it's clear that the company bought most of its growth here.

The question of profitability merits a bit more digging. Operating income growth (up 13%) lagged revenue growth, and while net income growth was a strong-looking 28%, a lot of that came from lower interest expense and a lower tax rate. Plenty of investors think that "growth is growth," but I'll be keeping a closer eye on margins for the next few quarters and monitoring management's ability to fatten margins in the acquired Pet's Choice business.

There are plenty of attractive aspects to this stock today. Veterinary care is not so economically sensitive, and even if PetSmart (NASDAQ:PETM) were to roll out its Banfield Hospital concept more aggressively, there would still be ample room for both players -- to say nothing of Banfield's geographic restriction to PetSmart store locations.

What's more, the two major components of the VCA Antech model feed off each other. Even though the hospital business is less profitable, more hospitals mean a bigger base to drive more higher-margin lab business. A sharper focus on diagnostic testing may in turn lead to better diagnosis and treatment of animals and happier pet owners and customers.

All the same, investors in VCA Antech should keep an eye on valuation, margins, and same-store revenue trends. Sometimes the dog that doesn't bark tells you the most.

Sit. Stay. Read more Takes:

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).