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

Abstract

Apart from being an energy source, dietary fibre is also discussed to act as anti-nutritional factor reducing apparent precaecal protein and amino acid (AA) digestibility due to reduced absorption or increased endogenous secretion or both. However, the amounts of protein and AA of endogenous origin determined at the terminal ileum in cannulated animals do not represent the total losses associated with endogenous secretion. A high proportion of secreted protein is reabsorbed and does not reach the terminal ileum, and losses occur during synthesis of endogenous protein. Therefore, the present study used an alternative indirect approach, taking the reduction of nitrogen (N) retention in a threonine (Thr) limited diet as a sensitive indicator for fibre-associated Thr losses. Two experiments were conducted with 12 castrated male pigs each between 37 and 75 kg body weight to measure the effect of the intake of Thr and 150 and 300 g/d fibre from wheat bran (Exp. 1), or 150 g/d fibre from rape seed, cassava leaves, and cassava root peels, respectively (Exp. 2), on N retention. During two (Exp. 1) and three (Exp. 2) balance periods the animals were subjected to the dietary treatments according to a cross-over design. All animals received 1350 g/d of a wheat-soybean-based diet supplemented with free AA to ensure Thr being the first-limiting AA. To determine the effect of Thr on N retention, intake of the basal diet was reduced to 1150 g/d and supplemented with corn starch to reach equal energy intake and an unchanged AA pattern. With increasing BW additional starch was added to all diets to ensure a constant energy intake of 1.25 MJ ME/kg BW(0.75). Since the fibre sources contained small amounts of Thr, N retentions were corrected for precaecal digestible Thr intake originating from the fibre sources according to the Thr effect on N retention as determined in experiment 1. Corrected N retentions were affected by fibre level (p = 0.007) and source (p < 0.001). Fibre-associated Thr losses amounted to 3.3, 3.2, 1.2, and 1.1 g/kg fibre from wheat bran, rapeseed, cassava leaf, and cassava root peel, respectively. It is concluded that Thr losses per gram of dietary fibre depend on the fibre source and that fibre concentration and source in pig diets should be considered as a factor affecting Thr requirement.

Effect of dietary fiber and threonine content on intestinal barrier function in pigs challenged with either systemic E. coli lipopolysaccharide or enteric Salmonella Typhimurium

“…Mucus is a major contributor to improved intestinal barrier function, facilitating an unstirred water layer and an environment that limits direct contact of luminal antigens with the epithelium. Dietary fiber (DF) is thought to have both direct and indirect effects on intestinal health and barrier function, including alterations in mucus secretion and cell proliferation as well as changes in the luminal environment as a result of fermentation metabolites [6,[11][12][13]. However, there are associated negative effects of feeding high DF on endogenous AA losses.…”

“…Losses of threonine (Thr) are particularly high because mucus contains high amounts of mucin, a Thr rich glycoprotein [14,15]. Since mucin is largely resistant to digestion, increased secretion of mucus will result in high endogenous losses of Thr [11,16]. Although mucin secretion is conserved and prioritized [17], there is evidence that mucin secretion might be sensitive to dietary Thr concentration [18].…”

Fibrous feedstuffs for the nitrogen retention of growing pigs

“…A large portion of NURI originates from absorbed and unused AA, either because they are above requirements or are unbalanced in relation to the ideal protein profile (NRC, 2012). Fibrous feedstuffs, especially those with high soluble fiber content, such as WB, increase the N and AA endogenous losses (BLANK et al, 2012) and thus may cause imbalance in the AA profile.…”

“…In general, the digestibility of neutral detergent fiber (NDF) is variable and dependent on its origin (LE GOFF & NOBLET, 2002). Even so, the effective contribution of NDF to the energy balance, for example, can be eventually considered null, because it increases endogenous losses and reduces the digestibility of other dietary nutrients (LIBAO-MERCADO et al, 2006;NOBLET, 2007;METZLER & MOSENTHIN, 2008;BLANK et al, 2012).…”

The role of dietary fibre in pig production, with a particular emphasis on reproduction

“…The inclusion of dietary fibres in pig diets is sometimes limited because they can have ant-nutritive properties. These include a reduction in the digestibility of dietary energy and protein [ 1 ] which may lead to inadequate amino acid, particularly threonine, absorption [ 2 ]. Although fibrous dietary constituents can have higher crude protein levels than non-fibrous constituents, on average approximately 30% of nitrogen is bound to neutral detergent fibres and therefore not available to the animal [ 3 ].…”