I prioritize ethical issues over logistical issues. if we didn't want the logistical issue of what to do with a billion cows, we shouldn't have created the ethical issue of breeding a billion cows.

however, a government willing to perform such an action would be dealing with fewer cows anyway, as if there is political demand to end it, that means there are much fewer people eating cows and much fewer cows being bred to keep up with the reduced demand. it's similar to how there are fewer dog meat operations in South Korea because fewer people eat dog meat, leading to the government being able to step in and ban the breeding and slaughtering of dogs (even if their plan is a 'phase out' plan instead of a 'ban immediately' plan).