Of all large dogs, probably the largest and heaviest of them all is an English Mastiff. There are mastiff dogs who can be as heavy as a ten-wheeler truck figuratively.  They can grow to about 200 pounds in weight and a minimum length of about 30 inches or 76 centimeters at the shoulder and some fully-grown ones can be as tall as a pony. The English mastiff is a combination of grandeur and good nature and they are considered as the gentlest dogs in all of the world in spite of their size.  But because of their immense size, special care must be exercised and you need to find some good English Mastiff training. If you have your own Mastiff already, the correct food intake is very important and over-feeding them is just as wrong as under-feeding. Yes, they need extra special care and attention and this what you should learn at this very moment.