Oyster shell

Oyster shell is a crushed calcium supplement offered to laying hens separately from their regular feed, letting each bird eat as much extra calcium as her own laying rate calls for. Heavy layers need noticeably more calcium than birds laying only occasionally, which is exactly why oyster shell works better offered free choice in its own dish rather than blended into the main feed for the whole flock.

Calcium demand rises directly with how often a hen lays, since each shell draws heavily on her calcium reserves, and a shortfall shows up fairly quickly as thin, soft, or oddly shaped shells, or in more severe cases as reduced bone strength over time. Layer feed already contains some added calcium, but many keepers find it is not quite enough for their most productive hens without a supplement on the side.

A common mistake is mixing oyster shell directly into a mixed-age flock's shared feed, where non-laying birds may eat more than they need, or skipping it altogether and only noticing a problem after eggshell quality has already declined. Keeping a small dedicated container in the coop, refilled as needed, is the simplest way to avoid both issues.