[Gizmo Baby]

Hi all, a quick question I read here how everyone suggests not to put a collar on our babies because it could cause a trachea collapse, now my two are starting obedience on Sat. and the trainer says the only way to train is with a collar, Gizmo weighs 13.4 pounds and Stellina weighs 7.3 pounds should I worry or is this warning for the smaller ones. Oh yeah please wish me luck lol