Our lab would run until she collapsed or found some food. Not many dogs designed to run at bike pace for 3 hrs. Trail hounds only run for about 10 miles or 45mins when in competition and they are super fit.
If I remember reading correctly its also been made illegal to give human medicines to animals quite recently, so you could be breaking the law too.
I just had Bonzo at the vets for his boosters.
The vet had a listen in to heart and lungs and tells me he's as fit as can be; more than probably due to running with bikes as she knows that's what we do. Low heart rate at rest just like his boss 🙂
He loves his bike rides and is pretty well behaved, except he did a lap and a half of the red/black at Drumlanrig t'other week with a bunch of mtbers (and their dogs) while I was out coaching the sproggs. Cheeky monkey didn't even ask if he could go play.
Returned him later with glowing reports and suggestions of flouro jacket and hiring him out as a 'trail 'guide dog as he knew the way round so well.
My tip for riding with dogs is to find a nice golf course with a lovely cool pond at the start of you ride. A damp lab runs much better! Returning for another dip at the end must be wonderful and I'm often tempted to join him!