Welcome aboard and congrats on your new family member~ Slow and steady growth is key to a healthy mastiff. As long as you can feel his last 3 ribs with little pressure, your pup is fit and trim. His adult weight will be about his parent's weight.
The following tips/suggestions are based on my experience as a dog mommy, forum member*s posts and volunteering at an animal shelter for a year.
*CRATE THE PUP
You want to crate train the pup. Make sure you have a blanket, stuffed animal (about their size) and white noise (ticking clock or ipod with soft music) so the pup can sleep. The pup is used to cuddling with siblings.
Make the crate the pup*s happy place to go to when he wants to sleep, decompress or just hang out.
*SECURE THE PUP NEAR THE FAMILY
You want to keep the pup in a room with a family member. Mastiffs need to be near their family members.
*FOOD
Find out what kind of food the shelter/rescue/breeder was feeding the pup and continue to feed it to the pup until you transition to a newer food, if you want. Most shelters/rescues use the cheapest food, meaning it is not very good for the pup.
Slow transition to the new food is as follows to prevent diarrhea. If at any time during the transition, the pup has diarrhea return to previous amounts of food per feeding. If you are switching flavors made by the same manufacturer, you should not have to do a slow transition.
Amount per feeding:
Day 1-4 ¾ cup of old food and ¼ cup of new food.
Day 5-9 ½ cup of old food and ½ cup of new food.
Day 10-14 ¾ cup of new food and ¼ cup of old food
Day 15 Start 100% of new food
Generally, mastiffs are allergic to grain and chicken found in kibble. You can check
www.dogfoodadvisor.com for dog food ratings and customer feedback. Mastiff puppies should eat Large Breed puppy food and they can continue to eat the food all of their lives or you can switch them to a Large Breed Adult Food at about 8-10 months.
http://healthypets.mercola.com/sites/healthypets/archive/2013/05/31/large-dog-feeding-mistakes.aspx
You may want to check out the raw diet for your pup. Check out the sub forum on raw diet that has a wealth of information. It is not recommended to feed the pup kibble and raw food. Dr. Becker talks about this in one of her videos.
Check out Dr. Becker*s videos on youtube.com for a lot of great information regarding the raw diet. Here is Part 1 there are 3 parts to the series. Well worth the time to watch the videos.
[video=youtube;Qx2YIIpF4cc]http://www.youtube.com/watch?v=Qx2YIIpF4cc[/video]
*PUP NOT EATING WHEN YOU FIRST BRING THEM HOME
They not used to their new environment and this is a natural behavior. Take the pup to a quiet place at meal times and sit and hand feed the pup. This will help the pup to eat when they are placed in a calm atmosphere, help you to bond with the pup and helps the pup establish trust with you. As they become settled, they will naturally follow your routine.
*PROTECT THE PUP FROM DISEASE
Keep the pup in your yard and place newspapers down where they will walk on the ground. Keep the pup away from dog areas unless they have had their 2nd set of shots, leaving the pup prone to infection with Parvo or other illnesses. This is very important!
*HOUSE TRAINING YOUR PUP
http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/house-training-your-puppy
*SOCIALIZE, SOCIALIZE AND SOCIALIZE SOME MORE
Socialize after they*ve had at least 2 round of shots preferably 3 rounds of shots to be safe. Prior to the 2[SUP]nd[/SUP] or 3[SUP]rd[/SUP] round of shots, keep the pup in your own yard. If that is not possible, bring newspapers with you for the pup to walk on. Avoid dog parks and areas with heavy traffic of animals.
*TEETHING
The pup will chew on anything they can find unless you re-direct the chewing. Provide frozen washcloths or small towels, nylabones, ropes, deer antlers, Kongs with frozen yogurt so they can chew to their heart*s desire. Some people use boxes, be aware that the pup will chew all boxes.
*TRAINING YOUR PUP
Start basic commands and reward with motivational treats (fav food or fav toy). Train for about 5 minutes per day and slowly increase the training time. Teach one command at a time. Once they master one command, move onto another command.
Number one command is sit. Teach the pup to sit, by placing a treat in front of his head and move it to the back causing him to sit to get the treat. When the pup sits, tell them good sit and give them the treat.
Second command should be "focus/look" This will help you tremendously when the pup is over 100 lbs. Put the pup into sit. With a treat in your hand (let the pup smell it), put the treat up to your eyes and tell the pup to look or focus. They may only do this for about 1-2 seconds. As soon as they look at your eyes, tell them good look or good focus and give the treat. Generally, mastiffs do not like to look anyone in the eyes for long because that means a challenge to them. Titan is up to 55 seconds of looking me in the eyes.
Other commands are "down/off", "leave it," "wait" (short pause), "stay" (pausing until you release) and "quiet/calm".
When you are training and when the pup does not do as you ask, then tell him no in a calm, stern voice and redirect back to the command. The only time a stern and loud NO should be used is when they are doing something that can cause harm to themselves or others.
Praise is the most powerful tool you have and the dog WANTS to please you. Show them clearly what you want, notice and praise when they comply, and learning goes much faster and pleasant for you both.
Mastiffs can be extremely stubborn and if you get frustrated with them, they will shut down. Mastiffs do not do well with yelling or hitting. Hitting can result in some unwanted mastiff behavior meaning fear aggression, which equals biting.
*LEASH TRAINING
Your pup will most likely not like the leash. Have the pup wear it around the house for a few hours each day and reward when the pup wears the leash with no issues.
If the dog pulls, do not walk until they stop and turn to look at you, then thank
them and start walking again. If they nip, put them away from you so they don't get attention--don't make it a game.
*PUPPY BITING/NIPPING/AROUND CHILDREN
Do not allow children and pup on the floor together. Pup will see them as playmates and nip at them. Picture the pup playing with their siblings.
Keep the pup on leash while the children are on the floor so you can have control of the pup. Pup and children should not be allowed to play alone.
If you puppy is biting/nipping, then try the following. This behavior can sometimes take a lot of patience and consistency in training.
They bite because that is how they played with their siblings.
When they bite, tell them “OW” in a high-pitched voice and “NO” in a stern, calm voice. NEVER HIT OR YELL AT A MASTIFF. They will shut down on you and ignore you.
When the pup stops biting, tell them to sit and reward. Tell him “good sit.”
Have the children hand fed the pup and help with training, i.e. teach the pup to sit, stay and come. This helps the pup to see them as non-playmates but as people in authority. These activities are great bonding exercises.
*EXERCISE
Puppies can exercise with natural movements and free play like running, stretching, playing on soft surfaces (grass and dirt). This type of exercise is actually healthy and good for their developing bodies but they do need to be able to pace themselves.
Structured exercise/play on hard surfaces and where they don't have they ability to pace themselves is where you need to be very careful. This type of exercise could harm the pup*s joints and bones. Puppies should not do any excessive exercise, i.e. walking, jumping, running and navigate stairs for the first 12 months to avoid injury.
Stairs should be maneuvered while on leash (even in the house) especially going down the stairs. Stairs should have carpet or rubber matting to give the pup traction. Mastiffs should be assisted up and down stairs until they are about age 12 months to prevent injury.
Most mastiffs can be very lazy but they still need to exercise. Generally, the amount of time to exercise is 5 minutes per each month of age.
*YOUR PUP AND HEAT (NOT THE FEMALE HEAT)
Remember, mastiffs do not tolerate heat. In the heat, reduce walk/exercise times. Have clean water available at all times. I freeze towels to either place on Titan or put on the floor for him to lie on in the summer to cool him off. Buy a kiddies* pool for the pup to play in to keep cool.
*DE-SEXING YOUR PUP
Mastiffs should not be neutered/spayed until 18 months to 2 years. NO MATTER what the vet says. Early neutering can cause growth problems and health issues.
[video=youtube;enPCZA1WFKY]http://www.youtube.com/watch?v=enPCZA1WFKY[/video]
Enjoy your baby! Have lots of patience! The pup will reward you with love and loyalty!
His name is Odin and he is 14 weeks today and he weighed in at 49.8 lbs he is going to be a big boy. I just want to make sure he is healthy, he still has his puppy belly but when you look down at his back you can see his bottom two ribs. He is not supper skinny but he has a belly. I am feeding him a raw diet and he seems to be thriving very well. My question is, how should I know he is at a healthy weight especially for his joints and muscular structure? All the vets around here have no experience with raw feeding and have no advice on it. Also, anyone have an idea on about how big he may get? I do understand there is no way to get an exact weight because every bb is different and have their own growth patterns. BUT an estimate would be appreciated 
