Looking for some advice. This is about my parents dog, but they have had him since before I left home I consider him my dog too iykwim.
So he is an 8 yr old pure lab (black), we have had him since he was 8 weeks old (straight from breeder). He is generally healthy with almost no health issues except for a large fatty lump (non cancerous) that was removed last year and fairly often gets ticks (from long grass walks). He is a very healthy weight and gets plenty of exercise (used to get 3 walks a day but seems happy with 2 now he's a bit older).
He is a beautiful dog, well behaved and obedient (puppy training, perseverence and also good luck) EXCEPT over food. In some ways he is brilliant - we taught him to "wait" before eating his dinner/treat. I can offer him the most special treat, say wait, put it on the floor in front of him (keep saying wait to remind him), walk away, even turn my back and he won't take it until told he can (and is always praised for waiting etc). However problems occur once he has whatever the food is. Even with just his normal dinner he is very aggressive if you go near him when he is eating - even if you aren't actually looking at him/just passing near or whatever. He will growl deeply, and if you don't go away will bare his teeth (an awesome sight) and if you continue (my sister is particularly bad for this) will "snap" at you - he has never actually bitten, I think it is just a warning but I worry that he would bite if it came to it. We deal with this now by just ignoring him when he is eating and praising good behaviour. If we have guests round we tend to shut him in a different room until he is finished his dinner just incase. But I now have an infact son and while I will never leave the two of them unatttended I would like to know if I can do anything to address this behaviour?
Thanks for reading, sorry that was so long but I wanted to explain properly and wanted to show both us and him in a good light (which I hope I have achieved).