By conifer, do you mean a particular kind? Some, like juniper and yew, are more poisonous and you don't want your rabbit eating any part of it. Cedar and redwood may not be as poisonous, as I don't see them listed on very many of the poisonous plants lists, but I do know the oils in cedar aren't good for rabbits. Conifers like firs, spruces, and pines, aren't a problem. Rabbits can have dried out pine cones and pieces of dried out pine wood, to chew on. My rabbits have even munched on the new soft needle growth on spruce trees, and seem to really like it.