Abstract
The primary objective of this experiment was to determine the effects of heat treatment on the standardized ileal digestibility (SID) of amino acids (AA) in corn distillers dried grains with solubles (DDGS) fed to growing pigs. The second objective was to develop regression equations that may be used to predict the concentration of SID AA in corn DDGS. A source of corn DDGS was divided into 4 batches that were either not autoclaved or autoclaved at 130°C for 10, 20, or 30 min. Four diets containing DDGS from each of the 4 batches were formulated with DDGS being the only source of AA and CP in the diets. A N-free diet also was formulated and used to determine the basal endogenous losses of CP and AA. Ten growing pigs (initial BW: 53.5 ± 3.9 kg) were surgically equipped with a T-cannula in the distal ileum and allotted to a replicated 5 × 4 Youden square design with 5 diets and 4 periods in each square. The SID of CP decreased linearly (P < 0.05) from 77.9% in non-autoclaved DDGS to 72.1, 66.1, and 68.5% in the DDGS samples that were autoclaved for 10, 20, or 30 min, respectively. The SID of lysine was quadratically reduced (P < 0.05) from 66.8% in the non-autoclaved DDGS to 54.9, 55.3, and 51.9% in the DDGS autoclaved for 10, 20, or 30 min, respectively. The concentrations of SID Arginine, Histidine, Leucine, Lysine, Methionine, Phenylalanine, or Threonine may be best predicted by equations that include the concentration of acid detergent insoluble N in the model (r2 = 0.76, 0.68, 0.67, 0.84, 0.76, 0.73, or 0.54, respectively). The concentrations of SID Isoleucine and Valine were predicted (r2 = 0.58 and 0.54, respectively) by the Lysine:CP ratio, whereas the concentration of SID Tryptophan was predicted (r2 = 0.70) by the analyzed concentration of Tryptophan in DDGS. In conclusion, the SID of AA is decreased as a result of heat damage and the concentration of SID AA in heat-damaged DDGS may be predicted by regression equations developed in this experiment.
Highlights
Production of corn distillers dried grains with solubles (DDGS) involves a drying step in which the temperature at the dryer inlet may be above 500°C, while the temperature at the dryer discharge may be above 100°C [1]
Heat treatment did not change the concentrations of Dry matter (DM), ash, or Crude protein (CP) in DDGS (Table 1)
Composition of distillers dried grains with solubles The concentrations of DM, ash, and CP were not affected by autoclaving DDGS and this observation supports results of González-Vega et al [4] who reported that autoclaving soybean meal did not change concentrations of DM, ash, or CP
Summary
Production of corn distillers dried grains with solubles (DDGS) involves a drying step in which the temperature at the dryer inlet may be above 500°C, while the temperature at the dryer discharge may be above 100°C [1]. During the acid hydrolysis step of AA analysis, Lysine that has reacted with reducing sugars is partially recovered, leading to an overestimation of available Lysine. For this reason, determination of reactive Lysine, color, and the Lysine:CP ratio have been suggested as approaches to estimate the availability of Lysine in DDGS [2,6,7,8,9]. There is, no information about effects of increasing time of heating of a specific source of DDGS on in vivo AA digestibility, and on the changes in reactive Lysine, and the Lysine:CP ratio. A second objective was to develop prediction equations that may be used to predict the concentration of SID AA in corn DDGS
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