I have never used any time of 'bread' or grains in my meatloafOur favorite is the stuffed and smothered.
2lbs of fresh ground meat (bison and beef is great)
1 C of finely diced onions, garlic and celery
spices (cumin, dry onions, garlic powder, quality salt and pepper)
mix well and with 2/3 of ground make a loaf with a long trough or well.
Stuff with chopped broccoli and cheese, or mushrooms and onions,garlic and melted butter, or cauliflower and bacon etc. and then apply the rest of meat as the top and pinch closed. Smother with a panful of sauce: pureed tomatoes, butter, spices, honey and fruit if desired
I use a lot of cumin and garlic powder and I think these powders thicken the meat and help it hold together.