How much do older dogs have to offer in their later years? A LOT. Consider Harley, a 6-pound dog who spent the first 10 years of his life living in a cage in a puppy mill.

Harley emerged from that experience with a missing eye, a broken tail, deformed legs, gnarled toes, infected teeth and heart disease. But don’t stop reading yet: This little dog’s story takes an immensely happy turn.

More than four years ago, rescuers scooped the Chihuahua up and gave him much-needed veterinary care. In 2011, Rudi Taylor, 54, and Dan Taylor, 60, of Berthoud, Colorado adopted Harley with the understanding that he might live two to three months. Instead, Harley thrived and became the mascot for a “Harley to the Rescue” campaign, which has raised money to help National Mill Dog Rescue save and care for more than 500 dogs to date. And, at a black-tie gala in Beverly Hills this month, Harley received a standing ovation when he was named American Humane Association’s 2015 American Hero Dog.

Rudi and Dan Taylor are overcome with emotion as they accept Harley’s award on Sept. 19, 2015 at the Hero Dog Awards in Beverly Hills. (Photo by Lori Fusaro)

“This is such an incredible opportunity,” Dan Taylor told me after Harley’s big showing at the Hero Dog Awards. “This is going to give us the chance to educate people about what happens in puppy mills.”

RELATED STORY: No longer caged in a puppy mill, Harley named 2015 American Hero Dog

Sept. 27 is National Puppy Mill Awareness Day, and at age 14 1/2, Harley is helping to put a spotlight on commercial dog-breeding operations across the United States. So is Victoria Stilwell, the renowned positive-reinforcement dog trainer and star of Animal Planet’s “It’s Me or the Dog.” Stilwell just posted a compelling YouTube video showing the bust of a large puppy mill that had been operating in Georgia since the 1980s. Like Harley, all the dogs in this video got nursed back to health and adopted:

In working on our book “My Old Dog: Rescued Pets with Remarkable Second Acts,” we saw firsthand that rescued animals like Harley are the most grateful — and the most forgiving — creatures you’ll ever meet. Please consider adopting dogs like Harley and giving them much-deserved remarkable second acts.

Rudi Taylor and Harley the dog (center) appear with Lori Fusaro (far left) and Laura T. Coffey (far right) at the Hero Dog Awards in Beverly Hills on Sept. 19, 2015. (Photo by Darrell Fusaro)

Love stories and photos of sweet senior pooches? The book “My Old Dog: Rescued Pets with Remarkable Second Acts,” written by Laura T. Coffey and with photographs by Lori Fusaro, is due out on Oct. 6. It’s available for now at Amazon.com and BarnesAndNoble.com.