Bioavailability of four calcium sources in the second-cycle egg-producing hens

In the second cycle of laying hens, egg production and quality decrease. This is mainly due to decreased absorption of calcium from the gastrointestinal tract. Hence, serum concentrations of calcium tend to decrease and are compensated through bone reabsorption. There are several sources of calcium with different solubilities and absorption rates. The choice of one of them may be of importance for the referred second laying cycle in hens. Hence, relative bioavailability (Fr) of 4 sources of Ca were evaluated in 300 Bovans-White 85-wk-old hens. Animals were randomly assigned to 5 groups as follows: the control group receiving baseline doses of calcium carbonate as required by this hen's linage (control group [GC]); GCca group (receiving additional calium carbonate); the GFtc group (receiving tricalcium phosphate); the GLgc group (which received calcium lactate-gluconate), and the GCcaCp group, which received calcium carbonate plus 10 μg of capsicum oleoresin (COr). Each hen was orally dosed with 1 g of Ca equivalent by probe, and serum Ca was quantified at predetermined times. The Ca-kinetic behavior was characterized by calculating the following: maximum serum concentration (CMAX); time to achieve CMAX; area under the concentration curve vs. time (AUC0-24). Fr as compared with GCca were calculated. GLgc and GCcaCp had the greatest CMAX and Fr values, that is, 34.7 and 37.2 μg/dL for CMAX and 109.6 and 112.9% for FR, respectively, and they were statistically indistinguishable between them (P