Effect of β-glucanase and β-xylanase enzyme supplemented barley diets on nutrient digestibility, growth performance and expression of intestinal nutrient transporter genes in finisher pigs

The study investigated the effect of dietary supplementation of an enzyme mix (β-glucanase and β-xylanase) to barley based diets that had different chemical compositions achieved through different agronomical conditions on growth performance, nutrient digestibility and intestinal nutrient transporters. Ninety-six pigs (44.7 kg (SD 4.88)) were assigned to one of four dietary treatments. The treatments were as follows: (T1) low quality barley diet, (T2) low quality barley diet supplemented with β-glucanase and β-xylanase enzyme supplement, (T3) high quality barley diet and (T4) high quality barley diet supplemented with β-glucanase and β-xylanase enzyme supplement. The inclusion of barley was 500 g/kg. There was an interaction between barley type and enzyme supplementation on average daily gain (ADG) and average daily feed intake (ADFI) (P < 0.05). Pigs offered the low quality barley diet supplemented with enzymes had an increase in both ADG and ADFI compared to the low quality barley diet only. However, there was no response to enzyme inclusion in the high quality barley diet. Pigs offered the low quality barley diet with enzymes had a higher coefficient of apparent total tract digestibility (CATTD) of gross energy (GE) compared to the low quality barley diet only (P < 0.05). However, the increase in the high quality barley diet with enzyme supplementation was not as great as with the low quality barley diet. Pigs offered the low quality barley had an upregulation in the expression of the ghrelin gene (GHRL) in the jejunum compared to pigs offered the high quality barley diet (P < 0.05). There was a barley × enzyme interaction observed for the expression of the cluster of differentiation gene (CD36) in the duodenum and the peptide transporter 1 gene (PEPT1/SLC15A1) and sodium-glucose linked transporter 1 gene (SGLT1/SLC5A1) in the ileum (P < 0.01). Pigs offered the high quality barley diet with enzymes had increased expression of CD36, PEPT1/SLC15A1 and SGLT1/SLC5A1 compared to the high quality barley diet alone. However the low quality barley diet with enzymes down regulated the expression of CD36, PEPT1/SLC15A1 and SGLT1/SLC5A1 compared to the low quality barley diet alone. In conclusion, offering a low quality barley diet supplemented with an enzyme mix improved ADG, ADFI and nutrient digestibility as well as modifying the expression of CD36, PEPT1/SLC15A1 and SGLT1/SLC5A1. The inclusion of an enzyme mix to the high quality barley diet improved nutrient digestibility and caused an upregulation in the expression of CD36, PEPT1/SLC15A1 and SGLT1/SLC5A1 but it did not improve animal performance.