Preheat oven to 325°F. Bake bread cubes on 2 large rimmed baking sheets until lightly toasted, about 20 minutes.
Sauté sausages in very large skillet over medium-high heat until cooked through, breaking into pieces with spoon, about 15 minutes. Using slotted spoon, transfer to large bowl; add bread.
Add onions and celery to same skillet and sauté until golden brown, about 10 minutes; transfer to bowl with bread.
Melt 1/4 cup butter in same skillet over medium-high heat. Add apples and sauté until tender, about 8 minutes; mix apples into stuffing.
Melt 1/4 cup butter in same skillet over medium-high heat. Add parsnips and sauté until golden, about 10 minutes; mix into stuffing.
Melt 1/4 cup butter in same skillet. Add sage and sauté until dark green, about 2 minutes. Mix sage and butter into stuffing. Season with salt and pepper.
Butter 15x10x2-inch glass baking dish. Stuff turkey. Transfer remaining stuffing to prepared dish; drizzle with 1/2 cup chicken broth. Cover with foil. (Can be prepared 4 hours ahead. Cover and refrigerate.)
**OR transfer all stuffing to a large, buttered baking dish & proceed as directed.**
Preheat oven to 350°F. Bake stuffing covered until heated through, about 1 hour. Uncover and bake until beginning to brown, about 10 minutes.