We now know that if we allow other countries to have undue leverage over us, they will eventually use it against us. Have to think long term here. What kind of Canada will my grandchildren inherit?
Isn't that already the practical reality when the USA has unfettered access to sell the food the animals eat in Canada? Having control over the milk supply doesn't offer much when you don't have any live cows in which to produce it with.
I suppose that explains why Canadian's won't allow the staple foods to also be supply managed, only accepting it for luxury foods (and once tobacco) that wouldn't cause a crisis if they disappeared, but on that realization we're back to dairy being more like taxis than essential calories.