362 Impact of dietary fiber and immune system stimulation on threonine requirement for whole body protein deposition in growing pigs.

Abstract

A nitrogen balance study was conducted to determine threonine requirement for optimal protein deposition (PD) when dietary fiber and immune system stimulation (ISS) were present alone and in combination. Ninety barrows (20.5 ± 0.75 kg initial BW) were randomly assigned to 1 of 10 dietary treatments (n = 9). Diets consisted of a low fiber (LF; 12.5% total dietary fiber) or high fiber (HF; 18.5% total dietary fiber from sugar beet pulp and wheat bran added at 15% of the LF diet in a 2:1 ratio) with graded levels of Thr [0.49, 0.57, 0.65, 0.73 and 0.81% standardized ileal digestible] fed at 2.2 × maintenance ME requirements. After 8 d adaptation, two 4-d collection periods (pre-ISS and ISS) were conducted. Immune stimulation was induced by repeated injections (i.m.) of increasing doses of E. coli lipopolysaccharide. Blood samples were taken during both periods to assess acute phase proteins and complete blood cell count. Data was analyzed separately for each period by PROC MIXED with fixed effects of period, Thr, and fiber and block as random effect. Threonine requirement was estimated using PROC NLIN quadratic plateau model. Concentrations of albumin, haptoglobin, fibrinogen, white blood cell count were affected by ISS (P<0.001). During pre-ISS, PD increased linearly (P<0.01) as Thr concentration in the diet increased with a significant interaction (P<0.05) between fiber and Thr. Similarly during ISS, PD increased linearly (P<0.001) with Thr concentration. Quadratic plateau model estimated Thr to optimize PD for LF and HF diets during pre-ISS at 0.68% and 0.78%, respectively. During ISS, Thr was estimated at 0.76% for LF diet and 0.72% for HF diet. High fiber and ISS independently increased Thr requirement for PD but these effects were not additive. Therefore dietary fiber may mitigate the effects of ISS on Thr required for immune response and optimal PD.