Is our dog sulking cos we're on holiday?

[Localher0]

Hoping to get a bit of advice.... we are on holiday abroad with a week more to go. We have a dog sitter looking after our two. He is staying at our house. He has old dog who is no problem and new dog who is causing us some concern.
New dog is a rescue border collie cross and we've had him since March. He's about 6-8 years old. Since we left he has gone right off his food and is fixated with being out in the garden, he's also had a bit of a tummy upset and is generally a bit off.
Because he has issues with cars and traffic I have had our trainer come in everyday to walk him while we're away and he's always really happy to see her.
We had a week away so at the end of July, we're home for 10 days and now away again.
I am hoping that his change in behaviour is just because his routine is off and he is missing the family being home. As he was an abandoned farm dog I'm also wondering if the being outside is a reverting to previous behaviour or he feels he's protecting the house while we're not there....
Has anyone else experience their dog being "depressed" and acting odd while they're away??

it sounds like he finally has some stability and then that's being "interrupted" by you going away. I find that most dogs miss their owners and act differently when they leave. You could also be the first people that he's properly bonded with, he will be confused and wondering when/if you're coming back. He's in the same environment that he's used to but the routine will all be different, and dogs like routine. I wouldn't worry too much about this behaviour (easier said than done though I know!), I'm sure he will perk up when he sees you again.

Ask the person who's looking after him to try and distract him, lots of games and mental stimulation, training or hiding/find it games etc

Thank you Saitama. I think you're right and fortunately he has settled down over the last couple of days so I'm not so worried anymore. He's a lot happier, eating again and being more affectionate with the sitter. Phew!!