Production performance and nitrogen flow of Shaver White layers housed in enriched or conventional cage systems

Despite the large number of studies examining the impact of cage systems on Ca and P nutrition, data are limited on the N balance of hens when housed under different systems. To this end, an experiment was conducted to assess N balance, manure characteristics, and indices of the performance of laying hens housed in 2 distinct caging systems. A total of 4,836 commercial Shaver White hens were housed in either enriched (EC) or conventional (CC) cages (average floor space per bird of 643 and 468 cm(2), respectively) under semicontrolled environmental conditions. Enriched cages provided hens with a curtained nesting area, scratch pad, and perches. Birds in both systems were phase fed similar layer diets for 11 periods (4 wk each). Data, expressed on a hen basis, were analyzed as repeated measures using the mixed model procedure of SAS. Lower feed disappearance (P < 0.01; 92.5 vs. 95.0 ± 0.6 g/d, DM basis) and manure output (P < 0.01; 79.8 vs. 91.3 ± 1.2 g/d, as-is basis, and 27.0 vs. 28.1 ± 0.2 g/d, DM basis) were observed in birds housed in EC compared with CC, respectively. Manure DM was 34.1 and 31.0 ± 0.3% for EC and CC, respectively. Egg production, feed conversion ratio, BW, egg weight, and egg mass were not significantly different between the 2 systems. Overall egg N output decreased with age for both cage systems and was not significantly different between the systems. Although no difference was observed in the overall manure N excretion (1.94 and 1.96 ± 0.02 g/d for EC and CC, respectively), hens housed in CC had a significantly (P < 0.05) higher N balance compared with those in the EC system (85.0 vs. 30.2 ± 13.6 mg/d, respectively), which could potentially be explained by a higher (P < 0.05) manure N excretion in the EC at the later stages of production. The current data provide estimates of the efficiency of N utilization in laying hens housed under different housing conditions.