No, it is not recommended to feed rabbits sumac branches. Sumac is a plant that can vary in species, and some species may contain compounds that are potentially toxic to rabbits. It's always best to err on the side of caution when introducing new plants or branches into a rabbit's diet.

If you're looking for safe and suitable branches for rabbits to chew on, it's best to stick with known rabbit-safe options such as apple, willow, or birch branches. These types of branches are generally safe for rabbits and can provide them with a natural and enjoyable chewing activity. However, always ensure that the branches are pesticide-free and sourced from non-toxic trees.