Modulation of Ileal Starch Digestion by Exogenous Fibres and Different Genotypes of Potato in Growing Pigs Fed a High‐fat Basal Diet
Authors: Wang Qi , Archbold Tania , Hayhoe Mychal‐Ann N , Yang Xiaojian , Sullivan Al , Bizimungu Benoit , Murphy Agnes , Ma David W , Duncan Alison M , Htoo John , Fan Ming Z 
Published: November 2023

The roles of exogenous fibres and novel cultivar genotypes (CV) of potato in influencing in vivo starch digestibility for nutritional management of human health need to be further established. Objectives of this study were to examine effects of dietary supplementation of two exogenous fibres, i.e., guar gum and cellulose, in combination with intrinsic fibres from six genotypes of potato on ileal dry matter and starch digestibility, intestinal fermentation and body weight gains in growing pigs fed a high‐fat basal diet. The basal diet was formulated as a zero‐fibre negative control (NC) to contain 41.5% poultry meal, 4% casein, 15% animal fat‐oil blend, 4.31% sucrose, 31% cornstarch, 0.50% salt and 0.40% trace mineral‐vitamin premix with crude fat contributing up to 37% of the dietary gross energy. The two exogenous fibre diets were formulated by diluting the NC basal diet with 10% guar gum and 10% cellulose at the expense of cornstarch, respectively. Six potato test diets were formulated by diluting the basal diet with 25.1% of one of the six genotypes of cooked and dehydrated potato tuber powder in combination with 8.5% guar gum at the expense of cornstarch to contain about 10% total dietary fibre. Titanium oxide was included (0.30%) as a digestibility marker. A total of 90 barrows were fitted with a simple T‐cannula at the distal ileum and fed the diets according to a completely randomized block design with each block lasting 28 d. Dietary supplementation of 10% guar gum, 10% cellulose and 8.5% guar gum in combination with each of six potatoes at 25.1% (Potato diets 1 to 6) increased (P<0.05) the distal ileal starch recovery and decreased (P<0.05) the ileal starch digestibility values compared with the NC diet. Three of the examined potato cultivar genotypes, i.e., CV12272‐3, CV96044‐3 and CVF05081, were associated with lower (P<0.05) starch digestibility and higher levels of resistant starch content compared with NC. Dietary supplementation of guar gum (10%) and 8.5% guar gum in combination with each of the six potatoes (Potato diets 1 to 6) at 25.1% increased (P<0.05) the distal ileal free glucose recovery compared with the NC. Moreover, 10% guar gum supplementation reduced (P<0.05) the abundance of the phosphorylated mTOR (Ser2448) in the proximal jejunum compared with the NC. Dietary supplementations of 10% cellulose, 10% guar gum as well as 8.5% in combination with six individual genotypes of potatoes did not affect (P>0.05) intestinal fermentation endpoints, weight gain and gain to feed ratio when feed intakes were controlled according to the NC. In conclusion, dietary supplementations of exogenous viscous fibre guar gum and non‐viscous fibre cellulose at 10% significantly reduced ileal starch digestibility with the 10% guar gum negatively affecting glucose absorption likely via the mTOR‐signaling pathway.Support or Funding InformationSupported by AAFC and the OMAFRA‐University Partnership Program.