Environment and Management

This study evaluated the effects of dietary Ca and P levels on laying hens housed in floor pens (F) or cages (C). Two hundred fifty-six 1-dold pullets, Lohmann Brown (B) and Bovan White (W) intermingled in equal numbers, were placed into 8 F. One hundred twenty-eight 1-d-old caged pullets were allocated into 32 layer C at 14 wk of age. Hens were given isocaloric and isoprotein diets containing either standard (STD) or 50% increased dietary Ca and P (CaP+) levels from 7 to 52 wk of age. Data was analyzed as a split plot factorial design with 4 replicates for each treatment combination. Housing systems and Ca and P levels were the main treatments and strains were considered subplots. At 30 wk, 80 floor raised hens and 48 caged hens were in vivo scanned to determine tibia bone mineral density (BMD). At 36 wk, hens were palpated to record keel bone deformities. From 25 to 52 wk, eggshell breaking strength and eggshell percentage were evaluated every 4 and 5 weeks, respectively. Independently of the housing system, B hens were heavier than W hens (P = 0.03). CaP+ had poorer BW uniformity (92 vs. 93%, P = 0.03), but had similar BW (P > 0.05) compared with STD hens. B, F and CaP+ hens had higher BMD compared with W (P < 0.0001), C (P < 0.0001), and STD (P = 0.081) hens. CaP+ diet reduced severity of keel bone deformities compared with STD diet when it was fed to C hens (P = 0.0008), but it did not influence F keel bones. C hens fed STD diet had higher number of twisted keel bones compared with C hens fed CaP+ diet and F hens fed STD diet (20.8 vs. 6.88%, P = 0.029). C hens fed CaP+ diet (P = 0.049) or CW hens (P = 0.016) had the largest amount of eggshell percentage compared with all the other birds. B hens fed STD diet laid more breakable eggs compared with W hens fed any of the 2 tested diets (P = 0.029). C hens laid eggs with more fragile eggshells compared with F hens (P = 0.031). Thus, the use of CaP+ diet for caged hens improved bone health and eggshell quality; however it might not have any improvements for floor raised hens.