July 03, 2012 06:50 PM

It was a sad day at Laila Ali s house Thursday when the world champion athlete and former Dancing with the Stars contestant and her husband, Curtis Conway, had to say goodbye to their beloved 10-year-old cane corso Italian mastiff Smokey.

Ali Tweeted the news Friday morning: “Sadly, I had to put my dog Smokey down last night I will miss him! This [triathalon] is for him!”

The athlete, who is “Mombassador” for the July 8 Aquaphor New York City Triathlon, tells PEOPLE she plans to dedicate her day to Smokey, whom she’s had since he was 10 weeks old.

“He was a stubborn sweetie pie!” she says, noting that he suffered from gastric torsion, also known as twisted stomach, a common condition with large-breed dogs. “His stomach flipped. He passed last night. The kids (son C.J., 3½, and daughter Sydney, 15 months) have not noticed yet. But my other dog Lanza (also a cane corso) is sad.”

I’m sad,” says Ali, who will star in the NBC reality Stars Earn Stripes on Aug. 13, “but happy he is out of pain and in dog heaven. My husband waited until they put him down so that his spirit could follow him home and guard the house. That’s what I hope, anyway.”

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