We have no clear idea what kind of shortages of perishable items we may be facing - not least because we have no idea how long customs checking and so on will take after a no-deal Brexit.
Our food industry is like many of our other industries. We have a "just in time" pan-European supply and processing network. For example, even if we have enough milk (at whatever price), we may lack the processing capacity to make all the butter, yoghurt and other dairy products that we need.
We may have enough beef, but we may lack the capacity to create the ready meals that the British population want. Even if there is sufficient food to provide adequate calories for everyone (and even then there is considerable doubt about that), if it isn't of a type and in a form that people want to eat then we will still have a food shortage.
We could be up to our ears in raw swedes and tripe but that doesn't mean that there won't be food shortages