a coon can cause some serious damage to even a full-grown dog! A border/lab mix won't be a really big dog either - a border collie weighs about 45lbs, not much more than a raccoon!
training. training. more training. Just like cleaning the coop and scooping poop and all the other jobs that come with having a pet. The only thing more necessary to a dog than training is food!
this is a cut/paste of my "training advice" As for the herding. No, I wouldn't do it. The main reason is that chickens don't "flock" like herd animals. Sheep will bunch together when scared, allowing the dog to move the flock where they need to go. Chickens scatter when they are scared. This will encourage the dog to chase them down. Also, a herding dog handles a sheep that refuses to obey by pushing/nipping/shoving the wayward animal where it needs to go. An older dog combined with birds that are used to THAT dog can be possible, but there is a ton of foundation training to be done.
With a border/lab mix I hope that you aren't just planning on putting him outside and leaving him. Both breeds have been selected for years to work one-on-one and have a need to have constant human interaction. Not to mention that both are extremely high energy breeds, especially as puppies. Add in the intensity of a border collie and the need for a job and the dog will make up his own fun. And a dog's idea of fun isn't something that people usually enjoy - barking, digging holes, chasing chickens, roaming to visit the neighbors, jumping the fence, and on and on. And turning him loose to run around won't touch it! You need to exercise their brain too! My GSD is not quite 2 and, even as a 4 month old pup, I was exercising and working him 2 hours a day. Now at 1 1/2, he runs 6 miles 3X a week, classes another night, training everyday as well as daily play sessions. And he is STILL ready for more.
You already know that he is excited with the chicks. Find the closest distance that the dog first notices the birds in the brooder. This might be in another room if he is one to constantly glance at the door. Put your dog on leash and get some extra special treats that he only gets for this work - bacon, grilled chicken (no spices!), hot dog chunks, etc. When the dog glances toward the birds, say his name and "leave it" If he looks at you, give him a treat - if he doesn't, give a light pop on the leash (think tap on the shoulder). When he looks at you reward him.
You can also teach him "watch me" the same way. You can practice this at random times though out the day. If you have a couple extra minutes while you're watching TV or whatever, just say his name, pause, "watch me" When he makes eye contact, then reward him. You can also (if you get in the habit of keeping a small treat in your pockets) catch him looking towards you say "watch me" and then reward. Or just praise him verbally.
Once the dog is reliably paying attention to you and the birds at a distance, move a little bit closer. If he absolutely blows you off, you're too close. Just back up a bit and begin again. Eventually you will be right amongst the birds. You can then start at a distance or with a long line (20' leash or so) and work from there. I never ever leave my dogs/chickens loose unattended together.
I don't even trust Rayden
I don't mean I constantly hover over the dogs when they are out with the birds, but I am in the area and aware of what they are doing. Think of it as a small child. Even though you've taught them not to play with matches, would you leave them alone in the house with matches scattered all over the floor?
The most important part of the training is to set the dog up to succeed. Don't give him a chance to chase the birds. Don't give him a chance to disobey.
ETA: The best thing about teaching "leave it" is that it works for everything. Drop something on the floor and don't want the dogs to touch it? "leave it" See dog running toward a snake? "leave it" Lots of training and work, but it pays off!
Of course, some dogs just can't be trusted off-leash. Period. They are just too focused on the birds. In that case, just confine the dog when the birds are out.