There is a big difference in how long it takes a small-breed puppy to mature versus a large-breed puppy. That’s because large breed dogs have much larger and longer bones than small breed dogs and they take longer to develop.
Large breed dogs can grow until they are 12 to 18 months of age. Contrast this with their small breed counterparts who will usually stop growing between 6 to 8 months of age.
Giant breed dogs, like Mastiffs, are a step bigger than large breed dogs and take even longer to reach their full growth. They can take up to two years to reach their adult size.
These dogs get to be massive with some weighing close to 200 pounds at maturity and they take a long time to grow.
Even after a dog has reached its full height and its skeleton is mature, it will also often continue to put on muscle and fill out, much like a human does.
This is often thought of as the “teenage” stage of dog growth although in reality the teenage stage is more often determined by behavior than looks.
Large and giant breed dogs can take up to three years to reach their full weight and completely fill out. Until that time they can seem out of proportion and lanky.
If you have a purebred puppy and you want to know how big it will be, the breeder should be able to give you a good idea. Purebred dogs are very predictable in behavior, size, and body structure and your breeder will be able to give you a range of expected height and weight based on your dog’s family tree.
Mixed breed puppies are harder to predict when it comes to adult size. You have to guess a lot. Paw size can be a good indication of how large a dog is going to get, but it’s not always accurate.
If you know how big both the parents are, then that can give you a pretty good idea as well.
Another way to tell if your mixed breed (or any) dog is still growing is to run your hands down its ribs. If your puppy has knobs on its ribs then they are also going to keep growing, because the knobs are active growth plates. Once your dog stops growing these knobs will fuse and you will no longer be able to feel them.
When Do Big Dogs Mature?
While dogs are considered adults when they reach one year of age, they can act like puppies for longer. Most dogs will reach maturity and stop acting like a puppy by the time they are around two years of age.
Mature dogs will be calmer in their demeanor, and they will be better at obeying commands and listening to you. You will also notice a decrease in the hyper energy that puppies typically have.
The most important factor that determines how large a dog will grow is genetics. Different breeds can grow to different sizes and the parent’s size also helps determine how large their offspring will be.
Early neutering before one year of age can also affect dog growth, but only by a few centimeters at the most. The ASPCA says that you can neuter a dog as early as eight weeks old.
For your large puppy to have the least amount of problems as it grows into an adult you need to make sure that it is being fed properly. Nutrition is important for all dogs, but it’s even more important for large breed dogs whose bones have a lot of growing to do.
Because large breeds have such big bones, you need to make sure they have a lot of calcium. You want to make sure that your puppy food label says: “[Pet Food Name] is formulated to meet the nutritional levels established by the AAFCO Dog Food Nutrient Profiles for growth or all life stages including growth of large-size dogs (70 lbs or more as an adult).”
This will ensure that the food has enough calcium, which can help prevent diseases like hip dysplasia down the line.
Most adult dogs only need to visit the vet once a year for their shots and annual wellness check. But puppies need to visit the vet more often.
They will start getting vaccinations when they are six to eight weeks old and get a final vaccination when they are about sixteen weeks old. Your vet can help you to determine the best vaccination schedule for your puppy.
With a large breed or giant breed dog, you will also want your vet to check for early signs of hip dysplasia, which forms as the dog is growing. There are early treatments for hip dysplasia if you catch the condition while your dog is young.
Puppies have tons of energy, but because their growth plates haven’t fused yet you need to be careful about the kind of exercise they get to prevent injury.
You don’t want to have them jog or walk on hard surfaces for extended periods while they are puppies. Instead, it’s a good idea to walk them on softer surfaces like grass or sand as much as possible until they are about 14 to 18 months of age.
Being careful about exercise in their puppyhood can help to protect your large breed dog from bone problems down the road.