By Theresa Gibilisco, owner, The Hungry Puppy
It's one of the most common questions at our feed counter, usually asked while someone is holding a 50 lb bag of layer feed in one arm and a little 7 lb bag of oyster shell in the other: "Do I really need both?" Here's how I answer it.
The short answer
For most backyard laying hens, yes. A small dish of oyster shell, set out separately, free choice. It's inexpensive, the hens that don't need it mostly ignore it, and the hens that do need it will thank you with better shells.
"But the layer feed already has calcium in it."
It does. A complete layer feed like NatureWise Layer 17% runs 3.7% to 3.9% calcium. For a lot of hens, that's plenty. But hens aren't all the same. A young hen laying almost every day, an older hen whose shells are getting thinner, a hen that eats a little less in the summer heat...they don't all need the same amount. Free choice oyster shell lets each one top herself off.
That's why Nutrena's directions for its layer feeds say to provide NatureWise Oyster Shell free choice after 16 weeks of age.
"Then why does my friend's Purina bag say she doesn't need it?"
Because Purina builds oyster shell into its Layena and organic layer feeds and says most flocks won't need extra. Even so, Purina recommends setting out a dish in hot weather. Different brands, different approach. Go by the bag you're feeding.
"What's actually in it?"
Crushed oyster shell and calcium carbonate. Nutrena guarantees 35% to 39% calcium. That's it. It's a supplement, not a feed, so it only works alongside a complete layer diet.
"Can I just mix it into the feeder?"
Please don't. If it's mixed in, every bird gets it whether she needs it or not, and the hens that need a lot can't pick out extra. Keep it in its own small dish or a wall-mounted cup near the feeder. Check it once a week and top it off.
"Who shouldn't get oyster shell?"
Nutrena labels it for birds 16 weeks and older, as extra calcium alongside a layer diet. Chicks and young pullets on starter grower shouldn't have it. Their feed is built with much less calcium on purpose.
In a mixed flock, it's still the easy answer. If everyone eats NatureWise All Flock 20% Pellet, which runs 1.4% to 1.9% calcium, Nutrena's directions add oyster shell free choice after 16 weeks so the laying hens get what they need. Nutrena's duck pellet label says the same for laying ducks.
"Is oyster shell the same as grit?"
No, and mixing them up is common. Oyster shell is a calcium source, and it dissolves as it's digested. Grit is insoluble crushed granite that stays in the gizzard and grinds food. Different jobs, different dishes. If your hens eat scratch, scraps or forage, they need NatureWise Poultry Grit too.
"How do I know if my hens need more calcium?"
- Thin, soft or rough shells
- Eggs that crack in the nest box
- Shell-less "rubber" eggs now and then
Check that oyster shell is out, that layer feed is most of what they eat, and that treats are under about 10%. If shell problems keep happening, or come with a hen who's acting sick, call a vet who sees poultry.
"How long does a bag last?"
A long time for a small flock, since they only take what they need. Keep the bag closed and dry between refills.
Add it to your next feed order
Oyster shell rides along with your feed on our own trucks, Tuesday through Friday on your town's route day, free with a $20 minimum. See our backyard chicken feed page and farm feed delivery page, or call 732-938-4470. Seeing thin shells and pale yolks? Read what layer feed does for your eggs.