# Synergistic Effects of 25-Hydroxyvitamin D3, Phytase, and Probiotics on Growth, Calcium and Phosphorus Metabolism, and Bone Development in Weaned Piglets Fed Low Ca-P Diets

## TL;DR

This study shows that combining 25-hydroxyvitamin D3, phytase, and probiotics improves calcium and phosphorus absorption and bone development in piglets on low-nutrient diets.

## Contribution

The novel finding is the synergistic effect of combining three supplements to enhance mineral metabolism and bone quality in piglets.

## Key findings

- Combined supplementation improved phosphorus digestibility and bone mineral density in piglets.
- The LHC group showed higher bone calcium content and better metabolic regulation than other groups.
- Supplementation increased beneficial gut bacteria and gene expression related to mineral transport.

## Abstract

Optimizing phosphorus utilization in animal feeds is a pivotal factor for sustainable livestock production, yet most current approaches focus on single additives rather than synergistic supplementation strategies. 25-hydroxyvitamin D3 (25-OH-VD3), phytase, and probiotics exhibit remarkable efficacy in enhancing the absorption and utilization rates of calcium and phosphorus in daily rations. The present study demonstrated that dietary supplementation with 25-OH-VD3, administered alone or together with phytase and probiotics, was associated with significant improvements in apparent phosphorus digestibility, calcium and phosphorus metabolism, and bone quality in weaned piglets. Additionally, the inclusion of 25-OH-VD3, whether as a standalone additive or in combination with phytase and probiotics, promoted the proliferation of beneficial gut bacteria. Collectively, these findings indicate that the synergistic application of 25-OH-VD3, phytase, and probiotics effectively boosts the utilization efficiency of calcium and phosphorus in animal diets.

Seventy 28-day-old weaned barrow piglets (Duroc × Landrace × Large White; 7.2 ± 0.20 kg) were used to determine the effects of 25-hydroxyvitamin D3 (25-OH-VD3) combined with phytase and probiotics on calcium and phosphorus metabolism and bone development. Five dietary groups were tested: basal diet + 50 µg/kg 25-OH-VD3 (CON); basal diet with 17% reduced calcium and phosphorus + 50 µg/kg 25-OH-VD3 (LCP); LCP + 50 mg/kg phytase (LH); LCP + 10 mg/kg probiotics (LC); LCP + 50 mg/kg phytase + 10 mg/kg probiotics (LHC). The experiment lasted for 31 days, including 3 days adaptation period. Apparent phosphorus digestibility was higher in the LH and LHC groups than in the CON group (p < 0.05). Bone mineral density and calcium content in metacarpal and rib bones were also higher in the LHC group compared with the CON, LCP, LC, and LH groups (p < 0.05). The jejunal mRNA expression of solute carrier family 34 members (SLC34A1, SLC34A2, and SLC34A3) members was higher in the LHC group than the CON, LCP, LC, and LH groups (p < 0.05), while the relative protein expression of the calcium-sensing receptor in the kidneys was lower in the CON group than in the LCP, LH, LC, and LHC groups (p < 0.05). Additionally, supplementation with 25-OH-VD3, either alone or in combination with phytase and probiotics, was associated with an increased abundance of beneficial gut bacteria. Overall, combined supplementation of 25-OH-VD3, phytase and probiotics enhanced bone development in weaned piglets fed a low-calcium, low-phosphorus diet by improving calcium and phosphorus utilization and calcium–phosphorus metabolic regulation.