A sustainable nutritional solution for fattening pigs based on 25-hydroxycholecalciferol and triterpenoids added to a low Ca diet containing phytase improves growth performance via the activation of muscle protein synthesis without compromising bone mineralization

Abstract

In the current climate of sustainable animal agriculture, nutritional strategies that support fattening swine growth performance and bone mineralization whilst reducing environmental impacts are much sought after. This study evaluated the effect of supplementing 25(OH)D3 with triterpenoids to a Ca-reduced diet containing phytase during the grower-finisher phase. Growth performance, bone composition, plasma metabolites and muscle gene expression were evaluated. Sixty crossbreed boar pigs (initial body weight (BW) 42.0 ± 5.1 kg at 12 wk of age) were assigned to three treatments with 20 pigs/treatment in a completely randomized design. Treatments comprised: 1) a standard commercial grower-finisher diet (positive control (PC)) containing 1,500 IU/kg vitamin D3 [3,585 kcal/kg digestible energy, 16.19% CP, 0.70% Ca, 0.29% standardized total tract digestible P]; 2) a negative control (NC) based on the PC with reduction in Ca and P (minus 30% and 10%, respectively); 3) the NC with vitamin D3 replaced by a commercially available compounds combination containing 25(OH)D3 and triterpenoids, dosed at 500 mg per kg of feed (TRT). All diets were provided ad libitum for 7 wk, and feed intake was recorded individually via electronic feeder stations. For the overall period, average daily gain and average daily feed intake were increased (P < 0.05) in TRT vs. NC or PC (+ 13.0% and + 8.3%, respectively, vs. NC); final BW was 7.8% higher vs. NC (+ 5.2% vs. PC; P < 0.05). Whole-body DXA-scanning at 19 wk of age showed that bone mineral density, content and percentage were reduced in NC vs. PC and equivalent to PC in TRT. Plasma 25(OH)D3 and P levels were raised in TRT (+ 33 ng/ml or 2.6-fold and + 0.55 mg/dL or 5.9%, respectively, vs. NC). The combination of 25(OH)D3 with triterpenoids was found to activate several biological pathways involved in muscle growth, including pathways that activate mTOR, a key central regulator of cell metabolism, growth, proliferation and survival when the gene expression was measured in the muscle tissue at 19 wk of age. These results suggest that the dietary combination of 25(OH)D3 with triterpenoids has the potential for use, alongside phytase, in supporting a reduction in Ca and P in the diet to reduce nutrient waste and improve the sustainability of production by promoting muscle growth and maintaining bone composition.