Help with injured deer

Emma,

I'm sure you have noble intentions here, but a positive outcome is highly unlikely. Based on the story I'd say the most likely case is that the deer injured himself trying to get free from the fence, or had been injured (perhaps in a car-deer accident) and then got stuck and couldn't get free. If he isn't up and walking within a day or two, then his odds of recovery are not very good. Even if a vet was to perform surgery, a surgically repaired animal usually does not fair well in the wild. I suggest that you open up the barn and let him wander out (before dawn and/or just before dusk). If he doesn't get up and head out within the next 24 hrs, then my advice would be to euthanize him.

I don't know the laws in Belgium, but if you have a governmental entity similar to what we call the Department of Natural Resouces (they manage wildlife, fisheries, etc) here in Michigan, then I would reach out to them. They might be willing or able to put the animal down humanely or at least give you a permit so you can.

I wouldn't keep him around and try to nurse him back to health if he doesn't pop back up on his own. A wild deer could be carrying diseases or parasites that could spread to your horses. In fact, since he allowed you to free him from the fence without thrashing wildly it implies that he was either too exhausted or that he is already sick (some diseases that affect deer cause them to lose their fear of humans). If he does heal up, then he may be accustomed to having people around by that time and that could potentially make him dangerous. Wild Deer (especially males) that become acclimatized to human contact can lose their flight response and become aggressive toward people. This happens most commonly in their breeding season (which should still be months away assuming the timeline is roughly the same there as here), but a deer that feels cornered may behave unpredictably at any time.