1. An experiment was performed to compare some methods of supplying calcium to intensively kept chickens.
2. The calcium content of a mash was adjusted to contain low (0·13%), normal (1·16%) and high (2·14%) amounts, and each of these mashes was fed to groups of chicks having access to: (a) no grit, (b) flint grit alone, (c) limestone grit alone, (d) both flint and limestone grit.
3. The addition of flint grit significantly improved the efficiency of food utilization on all diets, whether limestone grit was provided or not.
4. On all three mashes the total amount of calcium grit consumed was greater in the presence of flint grit than when it was fed alone.
5. As the level of calcium in the diet increased, the amount of limestone grit consumed decreased, whether it was fed alone or in the presence of flint grit.
6. The best results, judged on a live-weight basis, were obtained when the normal calcium mash was fed with flint grit alone, followed by the low calcium mash with both flint and limestone grit, followed by the normal calcium mash with no grit.
7. On the basis of the efficiency of food utilization, the low calcium diet with flint and limestone grit was best followed by the normal calcium diet with flint grit alone.
8. Access to limestone grit reduced the efficiency of food utilization in all but the low calcium diet.