16% is too low, scraping the bare minimum. You don't have to change feeds or percentages with the seasons. If you feed a 20% feed year-round, ideally a non-layer feed with calcium on the side, your flock will be all set and you won't have to change anything for seasons, chicks, roosters, retired/sick/molting hens, etc. I feed my mixed flock a 20% flock raiser feed year round, and they are happy and healthy. It's the Purina flock raiser and I'm very happy with it. You can also use a chick starter or grower, permanently.