My feed shop sells both oyster shell grit and flint grit. What is the difference and which is the best for my chickens?
Sonia Jenkins, Chester
Laurance Beeken replies: Oyster shell ‘grit’ is small stones and mollusc shells (not just oyster) mixed, and is what most people will find in their pet shops. The oyster shell is a hangover from old practices of adding sea shells in for calcium content to improve egg shell quality. Chickens, fortunately, are not stupid and will pick out the bits they need, invariably the stones, to use in the crop for food grinding. If choosing this option, check that there are stones included in the mix as you may find all shell, which is not much use for the birds.
Flint grit is just a mixture of small stones which provides grinding material for the crop. If you, in any way, doubt the benefits of oyster shell, then go for this option. Free range birds will naturally pick up small stones as they forage so this is the alternative most suited to their natural habit.
You will find a degree of ‘grit snobbery’ exists in breeders and enthusiasts as each one has their preferred type, but my recommendation would always be for flint grit only as there is little evidence that shells improve egg shell quality.