Mastiffs go through growth spurts. If he doesn't seem to put on weight for a few weeks, he might be building up for one of the spurts. 45 pounds at 4 months is a good weight. There will be months where he will grow in height and look like a gangly teenager, then his girth will catch up and it will start over again.
Answered by oltorf112 - 5/7/2014 1:58:08 AM