This would mean either that we would have a lot less food, or we would have to divert a lot of effort from other productive activities to make it up. Maybe that's okay, but still this idea is not free, and not low-hanging fruit.
Antibiotics allow us to produce animal products with reduced effort per unit than otherwise. If we ban antibiotics, it will require more effort to produce the same amount of animal products. That is true regardless of what happens on the money/profit side. This may be a fine tradeoff, but it's still a necessary tradeoff.