True ileal amino acid digestibility and endogenous ileal amino acid losses in growing pigs fed wheat shorts- or casein-based diets1,2

Abstract

Use of dietary AA in growing pigs reflects digestion and use of digested AA for various body functions. Before evaluating dietary effects on use of digestible AA intake for body protein deposition, a digestibility study was conducted to investigate true ileal AA digestibility and endogenous ileal AA losses in growing pigs fed graded levels of wheat shorts (WS) or casein (CS; control). A casein-based basal diet (basal) was formulated to contain 0.27 g of standardized ileal digestible (SID) Lys per MJ of DE, to which extra Lys was added from WS (WS2, +0.10 g of SID Lys per MJ of DE; WS3, +0.20 g of SID Lys per MJ of DE) or casein (CS3, +0.20 g of SID Lys per MJ of DE). A fifth diet was formulated to be similar in CP level and source as CS3 but in which 6% pectin, a source of soluble non-starch polysaccharides (NSP), was included at the expense of cornstarch (CS3 + pectin). Five Yorkshire barrows (17.5 +/- 1.5 kg of BW) were fitted with a T-cannula at the distal ileum and randomly assigned to 1 of the 5 experimental diets in a 5 x 5 Latin Square design. Apparent ileal digestibility (AID), true ileal digestibility (TID), and endogenous ileal protein losses (EPL) were determined using the homoarginine method. Diet CS level did not influence (P > or = 0.10) TID of most essential AA or EPL (10.4 g/kg of DM intake). Including pectin in the diet did not influence TID of AA (P > or = 0.10) but increased EPL (15.6 g/kg of DM intake; P > or = 0.01). Inclusion of WS in the diet reduced TID of most essential AA (P < 0.01). The TID values for most essential AA, however, were the same (P > or = 0.10) for both dietary WS levels, except for Lys and Met, which were further reduced at the greatest dietary WS level. Increased EPL (P < 0.01) was only observed for WS3 (16 g/kg of DMI). We concluded that (1) the effects of dietary protein source on AID of AA can be attributed both to reduced TID of AA and increased EPL, (2) the impact of dietary WS level on TID of AA and EPL does not seem to be linear, (3) soluble NSP from pectin or WS exerts a greater effect on EPL than insoluble NSP, and (4) because of the metabolic cost associated with EPL and the impacts of feed composition on microbial fermentation in the gut lumen, the effects of feed ingredients on the use of ileal digestible AA for protein deposition should be investigated further.

Nutritive value of wheat and wheat by-products in pig nutrition: A review

“…Bach Knudsen and Hansen, 1991). They stimulate the secretory output from salivary glands, stomach, liver, pancreas and intestinal walls (Low, 1989), and increase the viscosity of digesta (Annison, 1993;Barrera et al, 2004;Libao-Mercado et al, 2006) by aggregating into large networks or mesh-like structures as a result of entanglement of many very large polymers (Bedford, 1995). The NSP have encapsulating effects on other nutrients, and can act as a physical barrier, thereby decreasing nutrient hydrolysis and absorption (Nortey et al, 2007a).…”

Soluble arabinoxylan alters digesta flow and protein digestion of red meat-containing diets in pigs

“…NSP intake in the form of pectin is associated with decreased apparent protein digestibility, which is attributed partly to endogenous losses, such as increased secretions of saliva, mucus, or both [14,15]. Slower and more distal digestion is also associated with prolonged satiety, an effect referred to as the ileal brake.…”

Effect of dietary fibre on nitrogen retention and fibre associated threonine losses in growing pigs

“…On the one hand, fibre contributes to a significant proportion of the energy content in many feedstuffs depending on its content and degradability in the hind gut. On the other hand, dietary fibre may reduce apparent protein and amino acid (AA) digestibility or increase endogenous protein losses or both (Schulze et al 1994;Libao-Mercado et al 2006) by increased sloughing of intestinal mucosal cells and a higher mucus production (Sauer et al 1991). Increased secretion and reduced re-absorption of endogenous nitrogen (N) is affected by the level and source of fibre (Schulze et al 1995).…”