pooping inside, calcium requirements and exercise

Question
dear sameer,
i have a 5 month old male labrador. here are my concerns:
1)we potty trained him by the end of two and a half months and he was trained to use one corner of the balcony. now he has just completed 5 months of age and refuses to go outside. he will hold his bladder, no matter what, come back home and poop and pee in that corner of the balcony. have tried taking him out after sleep, food and play but with no avail yet. we live in an apartment and have only one balcony  which is now becoming unusable and cleaning it up each time is very difficult. please help.
2)would you have any ballpark figure for how much calcium is required by body weight for a growing lab. three different vets have given me three different advice. am confused.
3)how much exercise will my dog need as of now? we take him for half an hour walks twice a day at a medium pace after which he rests and is energetic again in an hour's time.
thank you so much for your time and patience.
eagerly awaiting your reply,
best regards,
ishita
(pune)
ps: my dog is best of friends with my neighbour's ferocious pit bull....probably the the only friend the latter has other than his master.thanks, again.

Answer
Hi Ishita,

I'll answer you queries as accurately as possible:

- You will need to be patient with his pooping routine. I suspect you take him for a hour walk. At 5 months its remarkable if he can hold his poo in for about an hour. If you are not taking him for long walks - start now. Reward him everytime he poos outside the balcony.

- Calcium is not a requirement - its a supplement. The idea is so that your lab's teeth and bones grow well. Not that they wouldn't otherwise ! The best advice i can give you is to take the advice of any of the Vets. I feed my dogs about 50 Mg of Calcium tabs - 3 times a week.

- At 5 months, your lab needs to be taken for a run. At least a 1 km run - once a day. If he runs now - his bones will become strong and you'll see his fur shine. Make him play with an old soccer ball so his teeth get stronger. And make sure you keep making him jump around - chase things and generally keep him active. Labs tend to become lazy very quickly.

All the best,

Sameer