Technological processes of feed manufacturing affect protein endogenous losses and amino acid availability for body protein deposition in pigs

In the pig, dietary protein value depends on the availability of amino acids (AA), usually estimated by way of ileal digestibility measurement. However, AA availability for body protein deposition is influenced by endogenous digestive losses specifically induced by feed components. The purpose of the experiment was to assess the impact of some feed manufacturing processes on AA ileal endogenous losses and their resulting availability for growth. Four technological treatments were applied to a wheat-sunflower meal mix and compared in vivo according to a 4 x 4 Latin square design. These treatments were two grinding conditions, leading to different particle sizes (1000 and 500 mum), and two pelleting processes, "regular" and "high-flow extrusion" (HFE), operated on the finest particle size only. Ileal specific endogenous losses and the coefficient of ileal real digestibility (CIRD) of AA were measured by way of the isotopic dilution method using N-15-leucine labelled pigs fitted with ileorectal anastomoses. The impact on nitrogen (N) and AA availability was assessed by N balance. Decreasing particle size from 1000 to 500 mum improved (P < 0.05) N (0.849 vs. 0.888) and AA (0.849 vs. 0.890 for valine) CIRD, as well as the ileal energy digestibility. In contrast to the regular pelleting process, the HFE process increased (P < 0.05) energy digestibility and improved (P < 0.05) N (0.792 and 0.824 for fine mash and HIE pelleting, respectively) and AA (0.795 vs. 0.840 for valine) coefficient of standardised digestibility (CISD). This effect of HFE was due to a significant decrease in N and AA endogenous losses (P < 0.05) rather than to a reduction in dietary protein ileal flow. However, due to the metabolic costs associated with the production of endogenous proteins, CISD variation could not accurately reflect the quantitative change in AA availability associated with the FIFE process. On the basis of N balance data, we could estimate these costs and defined coefficients of ileal standardised availability of N (CISA) for body protein deposition. The improvements in N CISD and N CISA due to the HFE process were 4.0 and 12.6%, respectively. (C) 2003 Elsevier B.V. All rights reserved.