63 Effects of Dietary Calcium and Phosphorus Deficiency on Growth Performance and Subsequent Recovery of Bone Mineralization in Replacement Gilts

Abstract

Abstract This study was performed to test the hypothesis that after a depletion period that renders replacement gilts more efficient in their use of calcium (Ca) and phosphorus (P), they can recover bone mineralization when fed a repletion diet. To this end, 24 gilts were fed according to a 2-phase feeding program (60–95 kg BW and 95–140 kg BW, respectively), corresponding to the period of depletion and repletion in Ca and P, respectively. The experimental diets for the first phase were a finisher control diet (D100; 2.1 g digestible P/kg) providing 100% of estimated Ca and P requirements or a finisher low-P diet (D60; 1.2 g digestible P/kg) providing 60% of estimated Ca and P requirements. In the second phase, one-half of the gilts from each finisher diet were randomly assigned to either a control (R100) diet or a high-P diet (R160; 3.5 g digestible P/kg) according to a 2 × 2 factorial design, resulting in 4 treatments: D60R100, D60R160, D100R100 and D100R160. Whole-body bone mineral content (BMC) and body composition of pigs were measured on each gilt at 2-week intervals by dual energy X-ray absorptiometry. Diets did not influence the growth performance throughout the experiment. At 95 kg, gilts fed D60 had reduced BMC and BMD (-9% vs D100; P < 0.001). At 140 kg, no significant effect of depletion diets was observed on BMC. These results show the high potential to limit dietary digestible P concentration during the growing period without causing any detrimental effects to gilts at mating, and they confirm the ability of replacement gilts to recover their BMC at 140 kg BW by increasing BMC deposition and their dietary Ca and P efficiency. Finally, high-digestible P content from 95-140 kg BW allowed gilts to increase BMC further, but required the use of dietary phosphates.