# Application of energy and nutrient reductions to a mixed-cereal diet without added inorganic phosphate, supplemented with a novel phytase alone or with a xylanase–β-glucanase combination, achieved a production benefit in pigs from wean to finish

## TL;DR

Adding phytase and other enzymes to a low-nutrient pig diet improved growth and reduced costs and environmental impact.

## Contribution

Demonstrated that enzyme supplementation can maintain pig growth while reducing feed costs and carbon footprint.

## Key findings

- Enzyme-supplemented diets maintained pig growth performance equal to a standard diet.
- Feed costs per kilogram of weight gain were reduced by 7.3% with the enzyme combination.
- Carbon footprint was reduced by 6.0–6.8% in enzyme-supplemented diets.

## Abstract

This experiment tested the hypothesis that supplementation of a nutrient- and energy-reduced mixed-cereal diet with phytase, xylanase and β-glucanase, over an entire wean-to-finish growth cycle, would result in growth performance outcomes that were not different from those achieved by pigs fed an unsupplemented, nutritionally-adequate diet. A total of 192 weaned pigs [DanBred × Pi, initial body weight (BW) 7.2 ± 0.4 kg] were assigned to 48 floor pens [4 pigs/pen (2 male, 2 female), 12 pens/treatment], in a completely randomized design. Diets included: 1) a nutritionally adequate wheat, corn and barley-based positive control (PC); 2) a negative control (NC) based on the PC but without added inorganic P, reduced in Ca, net energy (NE), digestible amino acids (AA) and Na, supplemented with PhyG at 1,000, 1,000, 750, 500 and 500 FTU/kg in starter I (7 to 11 kg BW), starter II (11 to 25 kg BW), grower I (25 to 55 kg BW), grower II (55 to 85 kg BW) and finisher (85 to 115 kg BW) phases, respectively (NC1 + PhyG low); 3) NC1 further reduced in Ca, digestible AA and NE, (by ≤ 0.03 percentage points, ≤ 0.01 percentage points and ≤ 9 kcal/kg, respectively) supplemented with PhyG at 2,000, 2,000, 1,000, 750 and 750 FTU/kg per phase (NC2 + PhyG high), and; 4) as 2) but further reduced in NE and digestible AA (by 26 to 33 kcal/kg and ≤ 0.01 percentage points, respectively), supplemented with 2,440 XU/kg xylanase and 304 U/kg β-glucanase (NC3 + PhyG low + XB). For the overall period, growth performance (all measures) was maintained in the enzyme-supplemented treatments to a level not different from the PC, whereas in starter II and grower I, BW was increased (+ 1.82 and + 5.11 kg/pig, respectively; P < 0.05) and gain:feed was increased (P < 0.05) in NC3 + PhyG low + XB, compared with the PC. Total estimated feed costs per kilogram BW gain (BWG) were lower (P < 0.05) in NC3 + PhyG low + XB (-0.05 € or 7.3%) and the carbon footprint of production was reduced in NC2 + PhyG high and NC3 + PhyG low + XB compared with the PC (by 128 and 145 g CO2 equivalents per kilogram of BWG, respectively, equivalent to reductions of 6.0% and 6.8%; P < 0.05). These results confirm the appropriateness of the applied energy and nutrient reductions for PhyG and PhyG with xylanase–β-glucanase in a mixed-cereal diet from wean to finish and highlight a potential feed cost saving and environmental sustainability benefit of the application.

This experiment has confirmed the appropriateness of prescribed dietary energy and nutrient reductions for use with a phytase enzyme at two dose levels, with or without a xylanase–β-glucanase combination, in a mixed-cereal diet without added inorganic phosphate, in pigs from wean to finish. The results will be of value in the future application of the tested enzymes in least-cost diets for pigs.