My boy looked skinny when he was young, too. I started adding tripe with his food. Mastiffs take about 4 years to mature, the last 2 is filling out. I feed my dog raw food, about 2-3% of his weight, more if he's active. They can look like they are more Great Dane than Mastiff early in their life but will thicken. Genetics will determine much of their final stature. Be patient. My dog has a skinny haunch and routinely weighs around 200 lbs. I bred him 5 years ago and the large male of that litter is nearly 250 lbs. You never know.
Answered by Anonymous - 10/27/2012 4:57:25 PM