Rearing cage type and dietary limestone particle size: I, effects on growth, apparent retention of calcium, and long bones attributes in Lohmann selected Leghorn-Lite pullets

Effects of rearing cage type and dietary limestone particle size (LPS) on growth, apparent retention (AR) of nutrients, and bone quality were investigated. The treatments were arranged in a 2 × 3 factorial with cage (conventional, CON and furnished, FUR) and LPS (fine, < 0.595 mm, F; medium, 0.595 to < 1.68 mm, M; and 1:1 mixture of F and M wt/wt; FM). A total of 900-day-old Lohmann LSL-Lite chicks were placed in CON (20 chicks/cage) and FUR (30 chicks/cage) based on BW. The diets were formulated according to breeder's nutrient specifications for starter, grower, and developer phases. At the end of 4, 12, and 16 wk of age (woa), 2 pullets/cage were euthanized for samples. At 12 and 16 woa, 1 pullet/cage was transferred to metabolism cages for AR measurements. There was no interaction (P > 0.05) between cage type and LPS on response variables. At 4 woa, body (P = 0.002) and bone (P < 0.05) weight was higher for CON than FUR pullets, but this was reversed (P < 0.01) at 16 woa. Pullets fed M LPS had higher (P < 0.05) AR of Ca, whole body mineral density (BoMD), and whole body mineral content (BoMC) than pullets fed F LPS. However, pullets fed F LPS had higher (P < 0.05) femur bone mineral density (BMD) and tended (P = 0.059) to have higher tibia bone breaking strength (BBS) than pullets fed M LPS at 16 woa. Pullets reared in CON cages had higher (P < 0.05) AR of Ca than FUR pullets. At 4 woa, CON pullets had lower (P < 0.05) femur and tibia BMD but higher tibia (93 vs. 83 N P = 0.012) BBS than FUR pullets. However, at 16 woa, FUR pullets had higher (P < 0.05) BoMD, BoMC, and tibia BBS than CON pullets. In conclusions, cage type and dietary LPS had independent effects on Ca utilization and skeletal development. Despite poor Ca retention, FUR caged pullets showed improved bone quality at 16 woa. Finer LPS improved femur mineral density suggesting coarser LPS had limited effects on pullet bone quality.