Evaluation of Aragonite as a Calcium source in laying hen diets

Experiments were conducted to determine the bioavailability of fine ground aragonite (FGA) using 0-14 d old broilers and to validate the use of FGA as a single particle size Ca ingredient on performance, eggshell quality, and tibia ash (TA) of laying hens from 28 to 56 wk. In Experiment 1, 450 Ross 708 broilers were fed 0.35, 0.43, 0.51, 0.59, and 0.67 % Ca using the addition of 0, 0.08, 0.16, 0.24 and 0.32 % Ca from either FGA or limestone (LS). Body weight, feed intake (FI), feed conversion ratio (FCR) and TA were measured at the end of 14 d. The relative bioavailability of FGA to LS was 179 % using slope ratio analysis of chick TA. In Experiment 2, 180 Hy-Line W-36 laying hens were fed diets containing 50/50 fine and coarse LS or 100 % FGA at 2.46, 3.28, or 4.10 % Ca using a 2 × 3 factorial. Interactions occurred for hen day egg production, egg weight, egg mass and feed efficiency. There were limited differences in performance regardless of Ca source or concentration, but the 4.10 % LS resulted in the lowest performance. An interaction was noted in that all FGA maximized TA in the laying hens, however, reduced LS feeding resulted in linear reductions in TA indicating Ca insufficiency at lower dietary concentrations. The fine/coarse mixture of LS increased shell quality compared to FGA ( P ≤ 0.05). These data indicate that FGA may be used as a higher available alternative Ca source in laying hens based on performance and tibia ash, but the combined use of coarse and fine Ca should continue to be used to support eggshell quality.