From the article, it looks like we're talking about two very different systems. Specifically, [1] refrigeration, [2] free-range versus laying houses and [2] ma

From the article, it looks like we're talking about two very different systems. Specifically, [1] refrigeration, [2] free-range versus laying houses and [2] mandatory vaccinations. You would likely need data from a range of countries to even begin to see which policies are most effective by data analysis.