255 Evaluation of Growth Performance and Bone Mineral Density in Grower Pigs Fed Phosphorus, Calcium, and Vitamin D Deficient Diets

Abstract

Abstract The objective of this study was to evaluate the effects of phosphorus, calcium and vitamin D deficient diets on growth performance and bone mineral density (BMD) in grower pigs. In two replicates, a total of 80 mixed sex pigs (26.7 kg BW) were allotted by BW and sex into individual pens across 5 dietary treatments (16 pigs/trt) for 28 days. Diets were: 1) Positive control (PC) diet containing monocalcium phosphate and no phytase, 2) PC diet containing phytase 1,500 FTU of Optiphos 2500, 3) Diet deficient in phosphorus (no monocalcium phosphate or phytase), 4) Calcium deficient diet (as diet 2 with no limestone), and 5) Diet deficient in vitamin D as diet 2 containing no added vitamin D. All diets were formulated to 3,297 kcal/kg ME, 1.15% SID Lys and contain the same AA:Lys ratios. Total Ca was formulated to be 0.76, 0.53, 0.45, 0.20 and 0.53%, with available P at 0.32, 0.32, 0.07, 0.32 and 0.32% respectively, for Treatments 1-5. Vitamin D was formulated to be at 154 IU/kg diet for Treatment 1-4. Pig BW and feed disappearance were recorded at the start and end of the study to calculate ADG, ADFI and G: F. On day 28, serum was collected, and all pigs euthanized to determine whole body bone, foot, rib, femur, and tibia BMD via dual x-ray absorptiometry. Data were analyzed with pen as experimental unit, fixed effect of dietary treatment, sex and their interaction, and initial BW block and repartition as random effects. Diet by sex interactions not observed (P >0.05). Compared with either Treatment 1 and 2, P and Ca deficient diets reduced ADG (0.96, 1.01, 0.80 and 0.91 kg/d, respectively (P < 0.001). The ADFI did not differ across dietary treatments. Vitamin D deficient pigs did not differ from either control treatments. Feed efficiency was different between treatments 1-4 (0.51, 0.53, 0.47 and 0.50, respectively, P < 0.001). Whole body BMD was reduced in the P and Ca deficient diets compared with Treatment 1 and 2 (0.582, 0.678, 0.803 and 0.758 g/cm2, respectively, P < 0.001). Similar results for 10th rib, femur, and tibia bones (P < 0.001). Vitamin D deficient diets reduced whole body and tibia BMD compared with Treatment 1 by 1.5% (P < 0.05). Gilts had greater whole body (0.762 vs. 0.703 g/cm2) and tibia (0.448 vs. 0.408 g/cm2) BMD compared with barrows (P < 0.05). In conclusion, dietary phytase provided similar performance and BMD to that of non-phytase control diet. Feeding P and Ca deficient diets for 28 days reduced pig growth and bone density, with P diets having more severe reductions. Further, while there was a slight reduction in growth there were no detrimental effects on bone mineralization in pigs fed vitamin D deficient diets.