This is a question that we often get from sitter and owners who work with Rover. Help the community out by answering them in our forum!
Grunting in dogs is possibly an involuntary action, caused by hard breathing that's reduced in pace. When your dog grunts and relaxes, he's not trying to put on a show of happiness. His emotions and comfort level are indeed genuine. Don't assume that grunting in dogs is necessarily always an indication of joy.
My dog grunts at me to get my attention. Normally it's because she wants to go outside or she wants me to wipe her face.( She's a Shar Pei so sometimes her wrinkles get dipped in the water and I have to wipe her face for her, lol ). IF the grunt is followed by some panting, it could mean they don't feel well and could have an upset tummy. If this is the case, check their stool to see if it's loose. If it's loose, I would recommend some organic canned pumpkin ( NOT pie filling ) , if the stool is fine, try some probiotic such as an organic PLAIN, non-fat yogurt ( I really like Nancy's ) that states probiotic on the container. This will help with settling the tummy. Plus probiotics are good for dogs to have on a regular basis anyways :)
I have a dog I pet sit that grunts and/or sighs when she lays down at the end of a busy active day or when we go to bed. So Funny! If a dog grunts as you approach (s)he could simply be giving you a hello. When I approach this particular pup, she will grunt and roll over for a belly rub. Sometimes she gives a soft grunt in her sleep and can be dreaming. But, it can ALSO be a sign of a respiratory or abdominal issue so observe the dog(s) normality and take it seriously if it seems out of characteristic for him/her.