Replacement of limestone with calcite prill derived from underground water in diets for molted layer hens

Two hundred and forty, approximately 100-week-old molted Hyline Grey layer birds were used to compare the efficacy of calcite (CaCO3) prill (derived from an underground water lime treatment process for the removal of hardness; hereafter referred to as ʹcalcite prillʹ) or limestone (ʹcontrolʹ) added as supplementary sources of calcium (Ca) to layer diets. One hundred and twenty birds were allocated to each diet. The 120 birds derived from 8 pens, with each pen comprising 5 cages each of 3 birds (15 birds per pen). The 2 diets were formulated to provide equal amounts of nutrients and vitamins and minerals, with the calcite prill and limestone added to each diet at 70 g/kg. Diets were offered on an ad libitum basis for 5 weeks. Measurements of bird performance, egg production, and egg quality were determined on a weekly basis. There were no statistical differences (P > 0.05) between the 2 diets in any of the indices measured over the experimental period. The average hen day percent was 73.2% and 69.5% for calcite-prill-fed birds and control birds, respectively. The lack of differences in egg production, egg weights, and egg quality seen between birds fed calcite prill and those fed limestone suggests that the Ca in calcite prill has a bioavailability at least equal to that for Ca from limestone. In this regard, calcite prill would appear to be a suitable alternative to limestone in diets for layer birds of this age.