Exogenous xylanase or protease for pigs fed barley cultivars with high or low enzyme inhibitors

Xylanase and protease inhibitors in cereals may be a reason for the varying efficacy of exogenous xylanase and protease in pig diets. The present study was conducted to evaluate the effect of xylanase and protease on the digestibility in pigs fed three barley varieties selected to be high and low in inhibitors. The cv. Invictus (spring barley) was selected to be low in xylanase inhibitors and cv. Hejmdal (winter barley) to be low in protease inhibitors, while SJ115158 (winter barley) was high in both xylanase and protease inhibitors. Growing pigs (34 ± 3 kg) were surgically fitted with a T-cannula in the terminal ileum and allotted to a 7 × 6 Youden square design, where 7 animals were fed with 7 diets for 6 weeks. Ileal samples were collected for 8 h on day 5 and 7 of each experimental week and fecal samples were collected from the first feces excreted on the same collection days. Titanium dioxide was added to all diets as an indigestible solid phase marker for the calculation of apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD). There was no consistent effect of variety or enzymes on the viscosity of ileal digesta. The ATTD of dry matter and organic matter was higher (P < 0.05) for Invictus than SJ115158, which was higher (P < 0.05) than Hejmdal. For Hejmdal, the AID of dry matter and organic matter was also lower (P < 0.05) compared to SJ115158. Supplementation of exogenous xylanase increased AID of dry matter, whereas the other evaluated components were unaffected. The ATTD of crude protein was lower (P = 0.027) for Hejmdal than for SJ115158 and exogenous protease increased (P = 0.004) ATTD of crude protein in both SJ115158 and Hejmdal. In conclusion, this study shows differences in nutrient digestibility among barley varieties and low efficacies of the selected exogenous enzymes independent of barley variety.