Effect of Particle Size on the Utilization of Calcium Supplements by the Chick

Four experiments were conducted using a total of 1480 broiler strain cockerels to determine the effect of particle size and source of calcium on chick weight and tibia ash. The particle sizes of the test calcium sources obtained from oyster shell and limestone were defined as 6–8, 16–20, 40–50, 100–140, and 270–Pan on a passed-retained basis using the U.S.B.S. sieve series. Non-screened samples of oyster shell, limestone and a mined marine source were also tested. No consistent differences in growth rate and percent tibia ash were observed between oyster shell and limestone when the particle size of these supplements was equal. Increased weight gains were obtained with the medium and fine particle sizes (U.S.B.S. 16–Pan) as compared to the larger sizes (U.S.B.S. 6–8). Tibia ash was significantly increased when the particle size of the calcium supplement was medium (U.S.B.S. 40–50) as compared to the ash values obtained by feeding either the smallest (U.S.B.S. 270–Pan) or largest (U.S.B.S. 6–8) particle sizes. Screen analyses of commercial limestone, oyster shell and the mined marine calcium source revealed that the commercial oyster shell was a larger sized material than either limestone or the mined marine source tested in this study. Increased tibia ash was obtained by feeding the commercial oyster shell product which verifies the need for a medium particle size (16–50) in the chick’s diet. These data indicate calcium utilization by the chick is dependent upon the particle size of the calcium supplement. It appears desirable to use a medium to fine (U.S.B.S. 16–Pan) particle size calcium supplement in chick diets when considering both chick weight and percent tibia ash.