I have a female lab mix, she'll be 11 in July, and she has been panting heavily for no apparent reason for the past week or so. She still has a healthy appetite and seems to have plenty of energy and interest in life. I feed her Nutro dog food and she takes a daily glucosamine supplement for her arthritis. She seems to be panting mostly in the evenings when we are relaxing. We're in Colorado and it's starting to get warmer outside, so I thought about the possibility that she hasn't shed her winter coat yet. And I also realize that she is no spring chicken! But she has been so healthy, not overweight, I guess I'm just concerned that this has seemingly come on quickly. I plan on taking her to the vet this week; I just wanted to see if anyone out there had any knowledge to share. Thanks much.