Calcium and phosphorus dynamics in commercial laying hens housed in conventional or enriched cage systems.

Calcium (Ca) and phosphorus (P) dynamics in Shaver White hens (19-63 wk of age) were compared between enriched (EC) and conventional cage (CC) systems. Calcium and P intake and their levels in egg components and excreta were considered. Using commercial levels of production (4,836 hens), 10 test cages/system (24 hens/test cage) were used as replicate units. Enriched cages provided a nesting area, scratch pad, perches, and more floor space (643 cm(2)/hen ) than CC (468 cm(2)/hen). All birds were offered similar phase-fed diets based on wheat-soybean formulation and housed under semicontrolled environmental conditions for 11 periods (28 d each). Egg weight, production, and shell quality indices (egg specific gravity, shell weight, thickness, and percentage shell) were also measured. Data were analyzed as a repeated measures design using the MIXED procedure of SAS. Egg production, weight, and shell quality measurements were not significantly different between the 2 systems. On a DM basis, EC hens exhibited lower feed disappearance than CC hens (92.5 vs. 95.0 ± 0.61 g/hen per day, respectively; P < 0.01), and lower Ca and P excretions in manure compared with CC hens (Ca: 2.11 vs. 2.29 ± 0.04 g/hen per day, respectively; P: 0.619 vs. 0.643 ± 0.005 g/hen per day, respectively; P < 0.01). Even though eggs from EC compared with CC had lower Ca deposition (2.07 vs. 2.13 ± 0.01 g/hen per day, respectively; P < 0.0001) and output (38.3 vs. 38.8 ± 0.15 mg/g of egg, respectively; P < 0.05), both EC and CC systems exhibited similar Ca outputs in eggs when expressed as a proportion of Ca intake (56.5 vs. 56.6 ± 0.51% Ca intake, respectively). The overall mean P retention between EC and CC hens was not significantly different (-7.22 vs. -7.45 ± 0.71% P intake, respectively), but Ca retention was higher in EC than CC hens (-1.37 vs. -4.76 ± 0.89% Ca intake, respectively; P < 0.05). In addition to providing environmental enrichment, EC systems may help to reduce Ca and P excretions when compared with CC systems, thereby improving the utilization of these nutrients.