There is no official requirement, but there is an understood requirement that it should be at least once a year.
Again, I'm going to speak to you from my understanding. I have a pretty good understanding of Ontario. At one time, it was in writing that a veterinarian had to be on those premises at least once a year. They have more recently removed that requirement, but they have given quite a lot of detail to define how often a veterinarian feels they need to be there. I think they define it to a level that veterinarians can make the proper judgment on whether it needs to be every two months, every year, etc. It is an absolute requirement to have a reasonable understanding of the practices and procedures that occur on that farm and the primary conditions there. Even within my own clientele, that time interval might vary.