At first glance, one of the most unusual displays in the Best Friends Art Project, which has been showing all this week in the Rotunda of the Russell Senate Office Building, is a simple dog house created out of 575 dog and cat collars.

The collars have obviously been used but most are still colorful, and inside the dog house is a soft pillow and a bright yellow tennis ball that is almost begging to be used for a game of fetch.

It isn’t until you read the display next to the exhibit that you learn that each collar came from an unwanted cat or dog that was euthanized at a pet shelter last year — together, they represent the 575 animals that were put to death every hour in American shelters in 2003, some 5 million animals in total.

The Best Friends Art Project was created by artist Cyrus Mejia and photographer Clay Myers of the Best Friends Animal Society, a group that runs the nation’s largest sanctuary for abused and abandoned cats, dogs and other animals. Along with the seven pieces from Mejia’s “575 Project,” the exhibit features seven other Mejia paintings and about 20 photographs from Myers.

“This work is all about the problem of homeless pets in the United States. It’s an issue that I think a lot of people are feeling more and more is a big problem,” said Mejia. “But it’s a problem that can be solved.”

Another striking exhibit by Mejia is a pencil on paper work called “The Screen of Self Defense.” The work forms a large picture of a dog and cat from 575 written explanations people have made for giving up their pets to animal shelters. They include “daughter went to college” and “barks too much.”

“When people come into a shelter they are asked why they want to give up their pets. These are some of the actual reasons they give. I did this piece with pencil and paper because it gives a very temporary feeling. I want people to think that these reasons don’t have a lot of substance to them.”

Along with Mejia’s work, Myers’ photographs depict dogs and cats he has come to know personally through his work as photo manager for Best Friends. Most of the animals he chose for his subjects are kept at the Best Friends animal sanctuary — which houses around 1,500 homeless pets at any given time — and some of his cuddly subjects are still waiting to be adopted.

The exhibit, which has been shown in Utah and Arizona and is heading on a six-city tour after it leaves Washington, is being sponsored on the Hill by Senate Minority Whip Harry Reid (D-Nev.) and Reps. Tom Lantos (D-Calif.) and Jerry Lewis (R-Calif.).

“This is an issue where support has been found across the board, from both liberals and conservatives,” Mejia said. “I’ve never met anyone that thinks this is a bad idea.”

And while Mejia said he is excited to have his work seen on the Hill — and is looking forward to the open reception being held at 5 p.m. Thursday in the Russell Rotunda — he said he has been especially inspired by comments from children who see his exhibit.

One such group was about 40 sixth graders from Fox Mill Elementary School in Herndon, Va., who were visiting the Hill on Monday. As they entered the Rotunda, they began splitting off into groups and excitedly checking out the exhibits and talking about their own pets. Standing among his classmates, Alexander Ramsey seemed proud to point out that his family had two cats and one dog — all adopted from his local animal shelter.