To date, there has been no study of protein molecular structures affected by bioethanol processing in relation to protein nutritive values of the new co-products of bioethanol production. The objective of the present study was to investigate the relationship between protein molecular structures (in terms of protein a-helix and b-sheet spectral intensity and their ratio and amide I to amide II spectral intensity and their ratio) and protein rumen degradation kinetics (rate and extent), estimated protein intestinal digestibility and total truly absorbed protein in small intestine (metabolisable protein) in different types of dried distillers grains with solubles (DDGS), such as wheat DDGS, maize DDGS and blend DDGS (wheat:maize ¼ 70:30). The protein molecular structures of the different types of DDGS affected by processing were identified using diffuse reflectance IR Fourier transform spectroscopy. The results showed that the protein structure a-helix to b-sheet ratio in the DDGS had a strongly negative correlation with estimated intestinal digestibility of ruminally undegraded protein (%dRUP, R 20·95, P¼0·04), tended to have a significant correlation with the protein PC subfraction (which was undegradable and contained proteins associated with lignin and tannins and heat-damaged proteins) (R 0·91, P¼0·09) and had no correlation (P. 0·10) with rumen degradation kinetics (rate and extent), total intestinally absorbed protein supply and degraded protein balance. However, the protein amide I to amide II ratio in the DDGS had a strongly positive correlation with soluble crude protein (CP) (R 0·99, P,0·01), protein PA subfraction (which was instantaneously solubilised at time zero) (R 0·99, P, 0·01), protein PB2 subfraction (which was intermediately degradable) (R 2 0·95, P¼0·04) and total digestible CP (R 0·95, P¼ 0·04). The amide I to amide II ratio also had strongly negative correlations with ruminally undegraded protein (%RUP: R 20·96, P¼0·03) and the degraded protein balance (OEB: R 20·97, P¼ 0·02), but had no correlation (P.0·10) with the total intestinally absorbed protein supply. Multiple regression results show that the protein structure a-helix to b-sheet ratio was a better predictor of %dRUP with R 2 0·92. The amide I to II ratio was a better predictor of the degraded protein balance with R 2 0·93 in the DDGS. In conclusion, the changes in the protein molecular structure a-helix to b-sheet ratio and the amide I to amide II ratio during bioethanol processing (either due to fermentation processing or due to heat drying) were highly associated with estimated protein intestinal digestibility and degraded protein balance, but were not associated with total intestinally absorbed protein supply from the DDGS to dairy cattle. The present study indicates that a potential novel method could be developed based on the protein molecular structure parameters to improve the estimation of protein value after a validation in a large-scale in vivo study is done.Protein molecular structures: a-Helix to b-sheet ratio: Amide I t...

The digestive characteristics of each DDGS component (dry matter, organic matter, crude protein and neutral detergent fiber), the hourly effective degradation ratio between N and organic matter, and the intestinal availability of rumen-undegradable protein differed significantly (P < 0.05) among wheat DDGS, blend DDGS and corn DDGS, and to a lesser extent between the different bioethanol plants. These results indicate that it is inappropriate to assume fixed rumen and intestinal degradation characteristics for DDGS without considering factors such as DDGS type and bioethanol plant origin.

The dramatic increase in bioethanol production in Canada has resulted in millions of tonnes of different types of coproducts: wheat dried distillers grains with solubles (DDGS), corn DDGS, and blend DDGS (e.g., wheat:corn 70:30). The objectives of this study were 1) to investigate the effect of DDGS type and bioethanol plant on the metabolic characteristics of the proteins and the total truly digested and absorbed protein supply to dairy cattle using the DVE/OEB system and 2) to compare the metabolic characteristics of the proteins of original feedstock grains with their respective derived DDGS samples. The results showed that all types of DDGS are a good source of the truly digested and absorbed protein in the small intestine [DVE; 107 vs. 249 g/kg of dry matter (DM) for wheat and wheat DDGS; 108 vs. 251 g/kg of DM for corn and corn DDGS]. According to the DVE/OEB system, the predicted total DVE supply to dairy cattle differed among wheat DDGS (DVE=249 g/kg of DM), corn DDGS (DVE=251 g/kg of DM), and blend DDGS (DVE=281 g/kg of DM) and, to a lesser extent, between the different bioethanol plants (DVE: 277 vs. 230 g/kg of DM for bioethanol plants 1 and 2). The results indicated the superior protein value of blend DDGS as well as that of the more optimum degraded protein balance (DPB) value for corn DDGS (DPB: 11 g/kg of DM in corn DDGS vs. 72 g/kg of DM in wheat DDGS and 55 g/kg of DM in blend DDGS). In addition, differences in the acid detergent-insoluble crude protein content of wheat DDGS samples were reflected in differing protein DVE values. In conclusion, it is inappropriate to assume fixed protein values for DDGS without considering factors such as DDGS type and bioethanol plant origin.

BackgroundAtlantic salmon production in Tasmania (Southern Australia) occurs near the upper limits of the species thermal tolerance. Summer water temperatures can average over 19 °C over several weeks and have negative effects on performance and health. Liver tissue exerts important metabolic functions in thermal adaptation. With the aim of identifying mechanisms underlying liver plasticity in response to chronic elevated temperature in Atlantic salmon, label-free shotgun proteomics was used to explore quantitative protein changes after 43 days of exposure to elevated temperature.ResultsA total of 276 proteins were differentially (adjusted p-value < 0.05) expressed between the control (15 °C) and elevated (21 °C) temperature treatments. As identified by Ingenuity Pathway Analysis (IPA), transcription and translation mechanisms, protein degradation via the proteasome, and cytoskeletal components were down-regulated at elevated temperature. In contrast, an up-regulated response was identified for NRF2-mediated oxidative stress, endoplasmic reticulum stress, and amino acid degradation. The proteome response was paralleled by reduced fish condition factor and hepato-somatic index at elevated temperature.ConclusionsThe present study provides new evidence of the interplay among different cellular machineries in a scenario of heat-induced energy deficit and oxidative stress, and refines present understanding of how Atlantic salmon cope with chronic exposure to temperature near the upper limits of thermal tolerance.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4517-0) contains supplementary material, which is available to authorized users.

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