I have a border collie who weighs in about 52 pounds and he's 6 months old. HIs mom was only 35 pounds and his dad 45 pounds. He doesn't seem overweight or anything, but he is significantly bigger than his parents. I was wondering when do border collie puppies stop growing?
According to my vet, the technical age is 18 months. But usually you can tell adult size by 9 to 12 months of age, especially if their weight plateaus at 9 months and doesn't change much in the next few months.