The effect of protease and xylanase enzymes on growth performance, nutrient digestibility, and manure odour in grower–finisher pigs

Rapeseed meal (RSM) and wheat dried distillers grains with solubles (DDGS) are byproducts which may be incorporated into pig diets. However, in comparison with wheat and soyabean meal, higher non-starch polysaccharide (NSP) content in RSM and DDGS may impose dietary limitations. Two 2 × 2 factorial experiments were conducted to investigate the interaction between xylanase (0 vs. 200 mg/kg) and protease (0 vs. 200 mg/kg) enzyme supplementation on (1) growth performance and carcass characteristics, and (2) apparent ileal (AID) and total tract nutrient digestibility (ATTD), manure gaseous emissions in grower–finisher pigs. In experiment 1, to assess growth performance, 128 pigs (body weight (BW), 34.2 ± 2.1 kg; n = 32) were allocated to one of four treatments based on a basal diet containing DDGS (300 g/kg) and RSM (210 g/kg): (1) basal diet; (2) basal diet plus 200 mg/kg protease enzyme; (3) basal diet plus 200 mg/kg xylanase enzyme; (4) basal diet plus 200 mg/kg protease and 200 mg/kg xylanase enzymes. In experiment 1, pigs offered diets supplemented with protease had a lower ADG (P<0.001) during the combined grower and finisher period (d 0-slaughter) compared with pigs offered diets without protease. There was an interaction between growing phase, protease and xylanase supplementation on ADFI (P<0.01) and BW (P<0.01). During the finishing phase (d 28-slaughter), pigs offered diets containing both xylanase and protease had a reduced ADFI and a reduced BW compared with pigs offered the protease or xylanase only diets. However, this interaction was not evident during the growing period (d 0–28). In experiment 2, 24 entire male pigs (BW 78 ± 2.3 kg; n = 6), were housed in metabolism crates and offered identical diets to those in experiment 1. There was an interaction between xylanase and protease (P<0.05) on the AID of GE. Diets containing protease only had increased AID of GE compared with basal fed pigs; however the AID of GE decreased when protease was combined with xylanase. Diets containing xylanase reduced manure odour emissions compared with diets without xylanase (598 vs. 1306 OuE/m3; P<0.05). In conclusion, protease increased the AID of GE and xylanase reduced manure odour emissions, however neither enzymes improved growth performance of grower finisher pigs offered diets based on RSM and DDGS.