Strategies To Improve Phosphorus Utilization In Growing Pigs: Depletion-Repletion Protocols

Abstract To optimize the use of dietary P by pigs, 5 feeding strategies were studied in a 3-phase feeding trial on 240 pigs (initial bodyweight (BW) of 31 kg): 1) C-C-C providing 100% of digestible phosphorus (Pdig, 4.3 g/kg STTD) and calcium (Ca, 9.7 g/kg) requirement to maximize bone mineralization, 2) L-L-L 60% of the Pdig and Ca requirements of C-C-C, 3) Phyt-Phyt-Phyt (phosphate-free, with phytase, 750, 686, 390 FTU/kg), providing 60% of Pdig and Ca requirements in phase 1, then 100%, 4) and 5) C in phases 1 and 3, and 60% of the need for Pdig in phase 2, associated with 65% of the requirements for Ca (N) or 80% (H), namely C-N-C and C-H-C. The BW and bone mineral content (BMC) were measured at the beginning and end of each phase. The BMC gain (gBMC), average daily gain (ADG) and average daily feed intake (ADFI) were calculated by phase. In phase 1, ADG was lower in the Phyt group than the C group (1.05 vs 1.10 kg/d, P < 0.01) and the BMC of group C and gBMC were higher than those of the Phyt and B groups (P < 0.05). In phase 2, C-C and Phyt-Phyt groups had similar BMC due to higher gBMC in the Phyt-Phyt (27.1 vs 18.4 g/d, P < 0.01). At the end of phases 2 and 3, C-C-C, C-N-C and C-H-C groups had similar BMC. The Phyt and B groups showed an increased phosphorus-use efficiency during phases 1 and 2 (+20% vs C). Phosphorus retention was also higher in the C-N-C and C-H-C groups, during the depletion in phase 2 (+24% vs C, P< 0.05). These results showed the potential of a depletion-repletion strategy including free phosphate diet to reduce phosphorus intake and excretion without affecting final growth performance and bone mineralization because of increased minerals utilization efficacies.