Date of Birth certificate omission is a BIG RISK.... You can include a cover letter explaining that you were not registered, and also you can get the No entry record from the Office that issues Certificates. This should be only done if you are totally unable to obtain DOB Cert.
However though seniors have advised that Matriculation Cert might suffice, but, remember it solely on the discretion of the Visa Officer.....if he sends it back due to NO Birth Certificate, you cannot do anything about it.
And also Application filling and compilation of the documents is a personal matter. CIO and Visa Office check Lists are absolute Guide
, all we have to do is complete the package to the best of our abilities. Some documents like IELTS, Forms, Marriage Certificate, Birth Certificate etc etc have been made compulsory, and, original are required to be sent (London Visa Office).
Just complete everything you can, and if something is omitted or you are unable to send, include a letter of explanation. You can take advice on the forum, but, its just an advice
Decision lies with you and the officer who will process your case. May be sometime the applicant is so strong and the visa officer thinks he will benefit greatly to Canada, or he had a bonus or bought a new Car or found a bag of money, or just fell in love with someone recently and is all rosy, they might overlook few things. Or may be the officer had a fight with his wife, is pissed at his Boss, or just is fed up of his monotonous job, and while processing your application will transfer the pain to you as well
SO prepare everything to the best of your abilities, as per Check Lists.