Heat-induced protein structure and subfractions in relation to protein degradation kinetics and intestinal availability in dairy cattle

Effects of amino resin-treated and heat-treated soybean meal on ruminal fermentation, nutrient digestion, and nitrogen partitioning in continuous culture

The objective of this study was to evaluate the effects of amino resin-treated soybean meal (SBM) on ruminal fermentation, nutrient digestion, and N partitioning. Treatments were: (1) untreated solvent-extracted SBM, (2) amino resin-treated SBM (AR-SBM), and (3) heat-treated SBM (HT-SBM). The experimental design was arranged as a replicated 3 × 3 Latin square with 6 fermenters in a dual-flow continuous culture system. Treatments were randomly assigned to fermenters within a Latin square for each period. Each fermenter was fed 106 g/d of diet DM equally distributed in 2 feeding times daily at 0800 and 1800. Diets were formulated to contain 16% CP, 30% NDF, and 30% starch across treatments. The experiment consisted of 3 experimental periods, each lasting for 10 d. The first 7 d of each period were considered adaptation, and the last 3 d were used for sampling and data collection. On d 8 and 9, samples were collected for analysis of diurnal variation in concentrations of NH3-N, pH, and VFA during the first 8 h after feeding. On d 8, 9, and 10, samples were collected from the liquid and solid effluents accumulated over 24 h for analysis of daily averages of NH3-N and VFA pools, and true ruminal digestibility estimates. Data were analyzed using the MIXED procedure of SAS and significance was declared when P ≤ 0.05. The model included the fixed effect of treatment and random effects of square, period, and fermenter within square, while time and interaction treatment × time were included for analyses of diurnal variation, with time as repeated measures. Compared with SBM, the cultured ruminal contents of AR-SBM and HT-SBM had lower NH3-N concentrations, indicating lower microbial fermentation of protein. Molar proportions of isovalerate and isobutyrate were greater in SBM than AR-SBM and HT-SBM, with greater molar proportion of isobutyrate for SBM particularly during the first 2 h after feeding. Flow of NH3-N was greater for SBM compared with AR-SBM and HT-SBM, whereas NAN flow, bacterial N flow, and N efficiency were greater for AR-SBM and HT-SBM compared with SBM. Our results indicate that both the amino resin and heat treatments of SBM allow for similar decrease in microbial degradation of CP without limiting microbial protein synthesis in diets with 16% CP. Amino resin treatment may be effective in reducing microbial fermentation of protein in the rumen without adverse effects on digestibility or fermentation parameters as compared with SBM.

A comparative study on the nutritional composition, protein structure and effects on gut microbiota of 5 fermented soybean products (FSPs)

In this study, we conducted an analysis of the differences in nutrient composition and protein structure among various fermented soybean products and their impacts on the gut microbiota of rats. Conventional physicochemical analysis was employed to analyze the fundamental physicochemical composition of the samples. Additionally, we utilized high-performance liquid chromatography and ELISA techniques to quantify the presence of antinutritional compounds. Fourier infrared spectroscopy was applied to delineate the protein structure, while 16 s rRNA gene sequencing was conducted to evaluate alterations in gut microbiota abundance. Subsequently, KEGG was utilized for metabolic pathway analysis. Our findings revealed that fermented soybean products improved the nutritional profile of soybeans. Notably, Douchi exhibited the highest protein content at 52.18 g/100 g, denoting a 26.58 % increase, whereas natto showed a 24.98 % increase. Douchi and natto demonstrated the most substantial relative amino acid content, comprising 50.86 % and 49.04 % of the total samples, respectively. Moreover, the levels of antinutritional factors markedly decreased post-fermentation. Specifically, the α-helix content in doujiang decreased by 13.87 %, while the random coil content in soybean yogurt surged by 132.39 %. Rats that were fed FSP showcased notable enhancements in gut microbiota and associated metabolic pathways. A strong correlation was observed between nutrient composition, protein structure, and gut microbiota abundance. This study furnishes empirical evidence supporting the heightened nutritional attributes of FSPs.

Effect of growing regions on morphological characteristics, protein subfractions, rumen degradation and molecular structures of various whole-plant silage corn cultivars

Little information exists on the variation in morphological characteristics, nutritional value, ruminal degradability, and molecular structural makeup of diverse whole-plant silage corn (WPSC) cultivars among different growing regions. This study investigated the between-regions (Beijing, Urumchi, Cangzhou, Liaoyuan, Tianjin) discrepancies in five widely used WPSC cultivars in China (FKBN, YQ889, YQ23, DK301 and ZD958), in terms of 1) morphological characteristics; 2) crude protein (CP) chemical profile; 3) Cornell Net Carbohydrate and Protein System (CNCPS) CP subfractions; 4) in situ CP degradation kinetics; and 5) CP molecular structures. Our results revealed significant growing region and WPSC cultivar interaction for all estimated morphological characteristics (P < 0.001), CP chemical profile (P < 0.001), CNCPS subfractions (P < 0.001) and CP molecular structural features (P < 0.05). Except ear weight (P = 0.18), all measured morphological characteristics varied among different growing regions (P < 0.001). Besides, WPSC cultivars planted in different areas had remarkably different CP chemical profiles and CNCPS subfractions (P < 0.001). All spectral parameters of protein primary structure of WPSC differed (P < 0.05) due to the growing regions, except amide II area (P = 0.28). Finally, the area ratio of amide I to II was negatively correlated with the contents of soluble CP (δ = -0.66; P = 0.002), CP (δ = -0.61; P = 0.006), non-protein nitrogen (δ = -0.56; P = 0.004) and acid detergent insoluble CP (δ = -0.43; P = 0.008), in conjunction with a positive correlation with moderately degradable CP (PB1; δ = 0.58; P = 0.01). In conclusion, the cultivar of DK301 exhibited high and stable CP content. The WPSC planted in Beijing showed high CP, SCP and NPN. The low rumen degradable protein of WPSC was observed in Urumchi. Meanwhile, above changes in protein profiles and digestibility were strongly connected with the ratio of amide I and amide II.

Feed Clusters According to In Situ and In Vitro Ruminal Crude Protein Degradation

Effective degradation (ED) of crude protein (CP) was estimated in vitro at 0.02, 0.05 and 0.08 h−1 assumed ruminal passage rates for a total of 40 feedstuffs, for which in situ ED was available and used as reference degradation values. For this, the Streptomyces griseus protease test was used. The differences between in vitro CP degradation and the in situ CP degradation values were lowest in legume grains and highest in cereal by-products and barley. The differences between in situ and in vitro ED were expressed using a degradation quotient (degQ), where degQ = (EDin vitro − EDin situ)/EDin situ. Among the tested feedstuffs, eight specific clusters were identified according to degQ for the assumed passage rates. The feedstuffs clustered in an unspecific way, i.e., feedstuffs of different nutrient composition, origin or treatment did not necessarily group together. Formaldehyde−treated rapeseed meal, soybean meal, wheat, a treated lupin, sunflower meal and barley could not be assigned to any of the clusters. Groupwise degradation (range of degQ for assumed passage rates are given in brackets) was detected in grass silages (−0.17, −0.11), cereal by-products together with sugar beet pulp (−0.47, −0.35) and partly in legume grains (−0.14, 0.14). The clustering probably based on different specific nutrient composition and matrix effects that influence the solubility of feed protein and limit the performance of the protease. The matrix can be affected by treatment (chemically, thermally or mechanically), changing the chemical and physical structure of the protein within the plant. The S. griseus protease test had reliable sensitivity to reflect differences between native feedstuffs and treatments (thermally or chemically) that were found in situ. The in situ results, however, are mostly underestimated. The clustering results do not allow a clear conclusion on the groupwise or feed-specific use of carbohydrate-degrading enzymes as pre- or co-inoculants as part of the S. griseus protease test and need to be tested for its potential to make this test more conform with in situ data.

Use of Heating Methods and Xylose to Increase Rumen Undegradable Protein of Alternative Protein Sources: 1) Peanut Meal

Peanut meal has an excellent total protein content but also has low rumen undegradable protein (RUP). High-performance ruminants have high RUP requirements. We aimed to evaluate the effects of processing peanut meal with an autoclave and conventional and microwave ovens, with and without using xylose on its ruminal kinetics degradation parameters and intestinal digestibility (ID). In situ studies were conducted to determine dry matter (DM) and crude protein (CP) rumen degradation kinetics. In vitro studies were conducted to evaluate intestinal digestibility (ID). The control treatment had a greater fraction A for DM and CP than peanut meals processed with an autoclave or conventional oven. The control had greater kd for CP compared with the microwave. The addition of xylose decreased fraction A, the degradation rate of fraction B (kd) and RUP, and increased the protein B fraction of autoclaved peanut meal. We observed a decrease in effective degradability (ED) and increased RUP for processed treatments in all experiments compared with the control. Processing methods did not affect the protein ID of autoclaved peanut meal compared to the control. An interaction between xylose and heating time was observed, where increasing heating time linearly reduced the ID of xylose-untreated treatments. Overall, these results suggest that the tested methods effectively increased the RUP content of peanut meal.

In situ ruminal disappearance of crude protein and phytate from differently processed rapeseed meals in dairy cows

BACKGROUND

The influence of different processing conditions of rapeseed meal on ruminal degradation of crude protein and phytate in dairy cows was investigated. Following oil extraction from the rapeseed, five residence times in the desolventizer/toaster were chosen to remove the solvent from the meal. Rapeseed cake and rapeseed meals were incubated in situ in the rumen of three fistulated dairy cows to determine ruminal degradation parameters.

RESULTS

With increasing residence time in the desolventizer/toaster the ruminal degradation of crude protein decreased significantly for every treatment step. Ruminal phytate degradation and crude protein degradation were affected almost identically.

CONCLUSION

The processing conditions of rapeseed meal have a major impact on the ruminal degradation of crude protein and phytate, indicating a potential conflict of interest regarding the production process. Large amounts of undegradable rumen protein are often intended for high-yielding dairy cows whereas a high level of ruminal degradation is preferred for phytate to increase absorption of phosphorus in the small intestine. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Associations of Protein Molecular Structures with Their Nutrient Supply and Biodegradation Characteristics in Different Byproducts of Seed-Used Pumpkin

The purpose of this experiment was to explore the relationship of protein functional groups (including amide I, amide II, α-helix, and β-sheet) in byproducts of seed-used pumpkin (pumpkin seed cake, pumpkin seed coat, and seed-used pumpkin flesh) with their nutrient profiles and biodegradation characteristics. The experiment was designed to use conventional chemical analysis, combining the Cornell Net Carbohydrate and Protein System (CNCPS) and nylon bag technology to assess the nutritional value and biodegradation characteristics of seed-used pumpkin byproducts. Fourier transform infrared spectroscopy (FTIR) was used to analyze the protein molecular structure properties of byproducts of seed-used pumpkin. In this study, we also applied correlation and regression analysis. The results showed that different byproducts of seed-used pumpkin had different in situ biodegradation, nutrient supplies, and spectral structures in the protein region. Among the byproducts of seed-used pumpkin, acid detergent-insoluble crude protein (ADICP) and neutral detergent-insoluble crude protein (NDICP) contents of the pumpkin seed coat were the highest, resulting in the lowest effective degradabilities (EDs) of dry matter and crude protein. The crude protein (CP) ED values were ranked as follows: pumpkin seed cake > seed-used pumpkin flesh > pumpkin seed coat. Significant differences were observed in the peak areas of amide I and amide II and the corresponding peak heights in the two peak areas in the molecular structure of the protein. The peak areas of amide I and amide II and the corresponding peak heights were at the highest levels for pumpkin seed cake, whereas there was no significant difference between the pumpkin seed coat and seed-used pumpkin flesh. Similarly, the peak heights of α-helices and β-sheets were highest for pumpkin seed cake. Correlation and regression results indicated that amide I and amide II area and height, α-helix and β-sheet heights, and area ratios of amide I: amide II, as well as the height ratios of amide I: amide II, and α-helices: β-sheets effectively estimated nutrient supply and that the height ratio of α-helices: β-sheets was mostly sensitive to biodegradation characteristics in different byproducts of seed-used pumpkin. There were significant differences in CP chemical composition and digestibility of different byproducts of seed-used pumpkin that were strongly related to the changes in protein molecular structures.

Combined molecular spectroscopic techniques (SR-FTIR, XRF, ATR-FTIR) to study physiochemical and nutrient profiles of Avena sativa grain and nutrition and structure interactive association properties

Synchrotron radiation based on Fourier transform infrared radiation (SR-FTIR), X-ray fluorescence (XRF) and attenuated total reflection based on Fourier transform infrared radiation (ATR-FTIR) spectroscopy are both fast determining and minimal sample preparing techniques. They are capable of detecting the internal molecular structures. However, these techniques are still not well understood by nutrition researchers for the analysis of feed. The purpose of this review is to introduce advanced SR-FTIR, XRF, and ATR-FTIR molecular techniques, use these techniques to study chemical and nutrient profiles of Avena sativa grain, and lastly to study the nutrition and structure interactive association properties. The review mainly focuses on the following aspects: 1) the background information of Avena sativa grain; its history, chemical composition, nutrient profile, inherent structure, and production; 2) molecular spectroscopic techniques; principles and spectral analysis methodology of SR-FTIR, XRF and ATR-FTIR; 3) the application of SR-FTIR, XRF, and ATR-FTIR as a novel approach. This review provides an insight on how molecular spectroscopic techniques could be used for the study of nutrition and structure interactive association properties.

Research progress and future study on physicochemical, nutritional, and structural characteristics of canola and rapeseed feedstocks and co-products from bio-oil processing and nutrient modeling evaluation methods

This article aims to review research progress and provide future study on physicochemical, nutritional, and molecular structural characteristics of canola and rapeseed feedstocks and co-products from bio-oil processing and nutrient modeling evaluation methods. The review includes Canola oil seed production, utilization and features; Rapeseed oil seed production and canola oil seed import in China; Bio-processing, co-products and conventional evaluation methods; Modeling methods for evaluation of truly absorbed protein supply from canola feedstock and co-products. The article provides our current research in feedstocks and co-products from bio-oil processing which include Characterization of chemical and nutrient profiles and ruminal degradation and intestinal digestion; Revealing intrinsic molecular structures and relationship between the molecular structure spectra features and nutrient supply from feedstocks and co-products using advanced vibrational molecular spectroscopy technique. The study focused on advanced vibrational molecular spectroscopy which can be used as a fast tool to study molecular structure features of feedstock and co-products from bio-oil processing. The article also provides future in depth study areas. This review provides an insight as how to use advanced vibrational molecular spectroscopy for in-depth analysis of the relationship between molecular structure spectral feature and nutrition delivery from canola feedstocks and co-products from bio-oil processing.

Effect of Revtech thermal processing on volatile organic compounds and chemical characteristics of split yellow pea (Pisum sativum L.) flour

Yellow pea (Pisumsativum L.) is an economically rich source of nutrients with health-promoting effects. However, the consumption of pea ingredients is minimal due to their off-flavor characteristics. The present study investigated the effect of Revtech heat treatment on the chemical profile and volatile compounds in split yellow pea flour. Revtech treatment (RT) was applied at 140°C with a residence time of 4 min in dry condition (RT 0%) and in the presence of 10% steam (RT 10%). Both thermal treatments resulted in a significant reduction (p < 0.05) in lipoxygenase activity and the concentration of key beany-related odors such as heptanal, (E)-2-heptenal, 1-octen-3-ol, octanal, and (E)-2-octenal. In addition, RT 10% resulted in a significant reduction in pentanal, 1-penten-3-ol, hexanal, and 1-hexanol compared to untreated flour. The content of known precursors of lipoxygenase such as linoleic and linolenic acids was found in higher concentrations in heat-treated flours, indicating the efficacy of Revtech technology in minimizing the degradation of polyunsaturated fatty acids. No significant changes in the amino acid composition or the 29 selected phenolic compounds in pea flours were observed with Revtech processing except for two compounds, caffeic acid and gallocatechin, which were found at higher concentrations in RT 0%. PRACTICAL APPLICATION: Thermal processing of split yellow pea flours at 140°C using Revtech technology successfully decreased the concentrations of volatile compounds responsible for beany off-flavor while improving the nutritional quality of studied yellow pea flours. These results provide valuable information to the food industry for developing novel pulse-based products with enhanced sensory characteristics.

The effects of pelleted dried distillers grains and solubles fed with different forage concentrations on rumen fermentation, feeding behavior, and milk production of lactating dairy cows

The physical form of feeds can influence dairy cow chewing behavior, rumen characteristics, and ruminal passage rate. Changing particle size of feeds is usually done through grinding or chopping forages, but pelleting feed ingredients also changes particle size. Our objective was to determine if pelleted dried distillers grains and solubles (DDGS) affected the feeding value for lactating dairy cattle. Seven lactating Jersey cows that were each fitted with a ruminal cannula averaging (± standard deviation) 56 ± 10.3 d in milk and 462 ± 75.3 kg were used in a crossover design. The treatments contained 15% DDGS in either meal or pelleted form with 45% or 55% forage on a dry matter basis. The forages were alfalfa hay, corn silage, and wheat straw. The factorial treatment arrangement was meal DDGS and low forage (mDDGS-LF), pelleted DDGS and low forage (pDDGS-LF), meal DDGS and high forage (mDDGS-HF), and pelleted DDGS and high forage (pDDGS-HF). Dry matter intake and energy-corrected milk were both unaffected by treatment averaging 19.8 ± 2.10 kg/d and 33.9 ± 1.02 kg/d, respectively. Fat yield was unaffected averaging 1.7 ± 0.13 kg/d, but protein yield was affected by the interaction of forage and DDGS. Protein yield was similar for both low forage treatments but was increased by when pDDGS was fed in the high forage treatment (1.05 vs. 0.99 ± 0.035 kg/d). When forage concentration was increased, starch digestibility increased by 1.9 percentage units, crude protein digestibility tended to increase 1.1 percentage units, and residual organic matter digestibility decreased 3.4 percentage units. Pelleting DDGS increased digestibility of neutral detergent fiber (NDF) digestibility (49.2 vs. 47.5 ± 1.85%) and gross energy (68.2 vs. 67.1 ± 1.18%). Increasing forage increased ruminal pH (5.85 to 5.94 ± 0.052). Passage rate slowed from 2.84 to 2.65 ± 0.205 %/h when feeding HF compared with LF. Rumination time increased from 417 to 454 ± 49.4 min with increasing forage concentration but was unaffected by the form of DDGS or the interaction of forage and DDGS. Eating time increased with pDDGS (235 vs. 209 ± 19.8 min), which may be a result of increased feed sorting behavior. Pelleting DDGS increased preference for particles retained on the 8-mm sieve and decreased preference for particles on the 1.18-mm sieve and in the pan (<1.18 mm). Results confirm that increasing forage concentration increases ruminal pH, rumination time, and slows passage rate, but contrary to our hypothesis increasing forage concentration did not increase NDF digestibility. Results also suggest that pelleted DDGS do not appear to affect milk production, ruminal characteristics, or passage rate, but pelleted DDGS may increase sorting behavior of lactating Jersey cows and increase NDF and gross energy digestibility.

Exploration of biodegradation traits in dairy cows and protein spectroscopic features in microwaved and moist heated tannin and non-tannin Faba bean

The objective of this study was to explore if microwave irradiation and moist autoclaving treatments could change nutritive values, nutrients availability and protein inherent spectral structural characteristics in tannin (var. Fatima) and non-tannin (var. Snowbird) faba beans. An in situ approach with four cannulated dry Holstein dairy cows was applied in this study. The results showed that beans heated with microwave and autoclaving had increased contents of ether extract and neutral detergent insoluble CP and reduced soluble CP, sugar and tannin concentrations when compared with the raw seeds. Heating reduced degradable nutrients in the rumen and increased intestinally absorbable nutrients, but it failed to improve digestibility in total tract. All the results showed heating with moisture and pressure would be stronger and severer than microwave irradiation. The variety of faba bean interacted with thermal treatment on total truly intestinally absorbed protein value which showed to be highest in the microwaved brown faba bean and lowest in the unheated Snowbird bean. The degraded protein balance (OEB) value was significantly decreased after both kinds of heating process, suggesting that heating treatments could mitigate loss of nitrogen from the rumen to a large extent. We further collected spectral data using mid-IR spectroscopy and found heat processed beans had varied peak height and area ratios compared with raw beans. However, multivariate results implied that heating process failed to completely change the whole molecular conformation in the protein amide region. Correlations were found between ADF/ADL and spectral features, and the OEB value was negatively related to protein secondary structural α-helix. In conclusion, both faba beans were more sensitive to autoclaving treatment than microwave irradiation in terms of nutrient availability in ruminants.

Application of advanced molecular spectroscopy and modern evaluation techniques in canola molecular structure and nutrition property research

This review aims to provide research update and progress on applications of advanced molecular spectroscopy to current research on canola related bio-processing technology, molecular structure, and nutrient utilization and availability. The studies focused on how inherent molecular structure changes affect nutritional quality of canola and its co-products from bio-processing. The molecular spectroscopic techniques (SR-IMS, DRIFT, ATR-FTIR) used for molecular structure and nutrition association were reviewed, including the synchrotron radiation with infrared microspectroscopy, the synchrotron radiation with soft x-ray microspectroscopy, the diffuse reflectance infrared Fourier transform spectroscopy, the grading near infrared reflectance spectroscopy, and the Fourier transform infrared vibrational spectroscopy. Nutritional evaluation with other techniques in association with molecular structure was also reviewed. This study provides updated research progress on application of molecular spectroscopy in combination with various nutrition evaluation techniques to current research in the canola-related bio-oil/bio-energy processing and nutrition sciences.

Micron-sized silica particles in wastewater influenced the distribution of organic matters in sludge and their anaerobic degradation

The influence of micron-sized silica particles on the distribution of organic matters in sludge and anaerobic degradation of macromolecular organic components (MOCs) in sludge was investigated. With the addition of micron-sized particles in the influent (VS/TS decreased gradually from 90.46 ± 0.21 % to 33.36 ± 0.17 %), the protein degradation percentage was significantly promoted while the polysaccharides degradation percentage was largely inhibited, resulting in the total MOCs degradation and methane production increasing firstly (with the promotion extent within 10 %) and then declining slightly, with the peak value at VS/TS of 56.03 ± 0.21 %. The shifted degradation percentage of protein and polysaccharides were caused by the significant changed distribution of organic matters in sludge. With the addition of micron-sized silica particles, the MW of EPS and secondary structure of protein in EPS changed little, which brought about little influence. While, the promoted extracellular protein content (so that the total protein content) and declined extracellular carbohydrates content (so that the total polysaccharides content), were found to be strongly correlated to the enhanced protein degradation and inhibited polysaccharides degradation. The results suggested that large amounts of grit in sludge might not be the main reason for lower degradability of sewage sludge in China.

Processing induced changes in physicochemical structure properties and nutrient metabolism and their association in cool-season faba (CSF: Vicia L.), revealed by vibrational FTIR spectroscopy with chemometrics and nutrition modeling techniques

This review aims to update recent progress in processing induced molecular structure changes in the association of physicochemical structure properties with nutritional metabolism in cool-season faba bean (Vicia L.), which was revealed using advanced vibrational molecular spectroscopy in combination with chemometrics and advanced nutrient modeling techniques. The review focused on strategies to improve the utilization of the cool-season faba bean through heat-related technological treatments and the relationship of the processing induced molecular structural changes to nutrient delivery and metabolism in ruminant systems. The updated methods with truly absorption nutrient modeling techniques and advanced vibrational molecular spectroscopy techniques sourced by globar and synchrotron radiation (e.g. NIR, near Infrared, FTIR, Fourier transform infrared, DRIFT, diffuse reflectance infrared Fourier transform, ATR-FTIR, attenuated total reflectance-FTIR, FTIRM, FTIR micro-spectroscopy, SR-FTIRM, synchrotron radiation- FTIRM) to study cool-season faba bean were reviewed. This article provides an insight and a new approach on how to combine advanced nutrient modeling techniques with cutting-edge vibrational molecular spectroscopic techniques to study the processing induced molecular structure change in relation to molecular nutrition of cool-season Vicia faba as well as the interaction between molecular structure and molecular nutrition.

In Vitro Methods of Assessing Protein Quality for Poultry

Protein quality assessment of feed ingredients for poultry is often achieved using in vitro or in vivo testing. In vivo methods can be expensive and time consuming. Protein quality can also be evaluated using less expensive and time consuming chemical methods, termed in vitro. These techniques are used to improve the user's efficiency when dealing with large sample numbers, and some mimic the physiological and chemical characteristics of the animal digestive system to which the ingredient will be fed. The pepsin digestibility test is the in vitro method of choice for quick evaluation of protein sample during quality control and in most research settings. Even though the pepsin digestibility test uses enzymes to liberate the amino acids from the protein, it does not mimic normal in vivo digestive conditions. The results obtained with this method may be misleading if the samples tested contain fats or carbohydrates which they often do. Multi-enzyme tests have been proposed to overcome the problem encountered when using the pepsin digestibility test. These tests use a combination of enzymes in one or multiple steps customized to simulate the digestive process of the animal. Multi enzyme assays can predict animal digestibility, but any inherent biological properties of the ingredients on the animal digestive tract will be lost.

Effect of extrusion of soybean meal on feed spectroscopic molecular structures and on performance, blood metabolites and nutrient digestibility of Holstein dairy calves

Objective

Performance and physiological responses of dairy calves may change by using extruded soybean meal (ESBM) instead of common soybean meal (SBM) in starter feed. The aims of the current study were i) to determine the effect of extrusion processing of SBM on protein electrophoretic size, fourier transform infrared spectroscopy (FTIR) structures and Cornell Net Carbohydrate and Protein System (CNCPS) protein sub-fractions and ii) to determine the effect of substitution of SBM with ESBM in starter feed of Holstein heifer calves during pre and post-weaning on performance, nutrient digestibility, and blood metabolites.

Methods

The SBM was substituted with ESBM at the level of 0%, 25%, 50%, 75%, and 100% (dry matter [DM] basis). Fifty heifer calves (initial body weight 40.3±0.63 kg) were used for the study. After birth, animals were fed colostrum for 3 days and then they were fed whole milk until weaning. Animals had free access to starter feed and water during the study.

Results

Extrusion of SBM decreased electrophoretic protein size and increased rapidly degradable true protein fraction, changed FTIR protein and amide II region. With increasing level of ESBM in the diet, starter intake increased quadratically during the pre-weaning period (p<0.05) and body weight, DM intake and average daily gain increased linearly during the post-weaning and the whole study period (p<0.05). Tbe DM and crude protein digestibilities at week 14 and blood glucose and beta hydroxybutyric acid increased linearly in calves as the level of ESBM increased in the diet (p<0.05).

Conclusion

Dairy calves performance and physiological responses were sensitive to SBM protein characteristics including electrophoretic size, FTIR structures and CNCPS protein fractions.

Infrared attenuated total reflection spectroscopic analysis and quantitative detection of forage spectral features in ruminant systems

This study aimed to (1) access protein molecular structure profile and metabolic characteristics of model forages [Foreign sourced-origin (coded as: "FSO", n = 7 vs. Chinese sourced-origin alfalfa hay "CSO", n = 5] in ruminant systems; (2) Quantify the relationship between forage protein molecular structures and protein utilization and availability. Advanced non-invasive vibrational molecular spectroscopic technique (ATR-FTIR: Attenuated Total Reflection Fourier Transform Infrared spectroscopy) with chemometrics was applied to reveal forage protein molecular structure. Both univariate and multivariate molecular spectral analyses were applied to study molecular structure features in model forages. The molecular structure study provided the detailed protein structure profiles of Amide I and Amide II areas and height, total Amide I and II area ratios, Amide I to II height ratio as well as Amide I to II area ratio using ATR-FTIR spectroscopy. The results showed FSO and CSO had similar (P > 0.05) protein rumen degradation kinetics. However, FSO had superior quality than CSO in intestinal (IDP) and total digestible protein (TDP) and truly absorbed nutrient supply (P < 0.05). As intestinal digestion of protein, FSO was higher (P < 0.05) in protein digestion in terms of: intestinal digestibility of rumen undegraded protein (dIDP: 47.5 vs. 38.3 %RUP); Intestinal digestible protein (IDP: 17.6 vs. 13.7 %CP). As truly absorbed nutrient supply, FSO contained higher (P < 0.05) truly absorbed rumen synthesized microbial protein, absorbable rumen undegradable feed protein in the small intestine, total truly digested protein in the small intestine, metabolizable protein and Feed Milk Value (FMV^DVE: 1.2 vs. 1.1 g/kg DM). The molecular structure-nutrition interactive relationship study showed that protein molecular structure profiles were highly associated to protein rumen degradation kinetics, significantly correlated to protein subfractions, protein intestinal digestion, and truly absorbed nutrient supply in ruminant systems.

Modification of Glutenin and Associated Changes in Digestibility Due to Methylglyoxal during Heat Processing

Glutenin is the main protein of flour and is a very important source of protein nutrition for humans. Methylglyoxal (MGO) is an important product of the Maillard reaction that occurs during the hot-processing of flour products, and it reacts with glutenin to facilitate changes in glutenin properties. Here, the effects of MGO on glutenin digestion during the heating process were investigated using a simulated MGO-glutenin system. MGO significantly reduced the digestibility of glutenin. The structure of MGO-glutenin and physicochemical properties were studied to understand the mechanism of the decrease of digestibility. These data suggest that changes in digestibility were caused by decreases in surface hydrophobicity and increases in disulfide bonds. MGO induces strong aggregation of glutenin after heating that led to the masking of cleavage sites for proteases. Moreover, carbonyl oxidation induced by MGO leads to intermolecular cross-linking of glutenin that increasingly masks or even destroys cleavage sites, further decreasing digestibility.

Assessing availability of amino acids from various feedstuffs in dairy cattle using a stable isotope-based approach

Nitrogen efficiency in dairy cows can be improved by more precisely supplying essential amino acids (EAA) relative to animal needs, which requires accurate estimates of the availability of individual EAA from feedstuffs. The objective of this study was to determine EAA availability for 7 feed ingredients. Seven heifers (258 ± 28 kg BW) were randomly chosen and assigned to 8 treatment sequences in a 7 × 8 incomplete Latin square design. Treatments were a basal diet (BD), and 10% (on a dry matter basis) of BD replaced by corn silage (CS), grass hay (GH), alfalfa hay (AH), dried distillers grain (DDGS), soybean hulls (SH), wet brewers grain (BG), or corn grain (CG). Total plasma AA entry rates were estimated for each EAA within each diet by fitting a 4-pool dynamic model to observed plasma, ¹³C AA enrichment resulting from a 2-h constant infusion of a ¹³C algal AA mixture. Individual EAA availability from each test ingredient was determined by regression of entry rates for that AA on crude protein intake for each ingredient. The derived plasma total EAA entry rates for corn silage, grass hay, alfalfa hay, dried distillers grain, soyhulls, brewers grain, and corn grain were 30.6 ± 3.4, 27.4 ± 3.2, 31.3 ± 3.4, 37.2 ± 3.2, 26.4 ± 3.2, 37.8 ± 3.2, and 33.5 ± 3.2% (±standard error) of EAA from each ingredient, respectively. Using the previous estimate of 8.27% EAA utilization by splanchnic tissues during first pass, total rumen-undegradable protein EAA absorbed from the gut lumen was 33.4, 29.9, 34.1, 40.6, 28.8, 41.2, and 36.5% of the EAA in each ingredient respectively.

Vibrational spectroscopic study on feed molecular structure properties of oil-seeds and co-products from Canadian and Chinese bio-processing and relationship with protein and carbohydrate degradation fractions in ruminant systems

The objective of this study was to apply ATR-FTIR spectroscopy to reveal feed molecular structure properties of oil-seeds and co-products and relationship with protein and carbohydrate degradation fractions in ruminant systems. The oil-seeds and co-products were from both various bio-processing industries in Canada and China. The protein and carbohydrate degradation fractions were evaluated with updated CNCPS system. Results showed that in the co-products from canola processing industries there are strong relationship between 1) soluble true protein (PA2) fraction and the following protein molecular structure spectral characteristics; spectral peak area of amide I and amide II (r = 0.56, P = 0.001), area of amide I (r = 0.67, P < 0.001), height of amide I (r = 0.74, P < 0.001), amide I and II ratio (r = 0.57, P = 0.001), α-helix (r = 0.82, P < 0.001), and β-sheet (r = 0.61, P < 0.001), 2) slowly degradable true protein (PB2) fraction and height of amide I (r = -0.60, P = 0.001), α-helix (r = -0.72, P < 0.001), and β-sheet (r = -0.51, P = 0.004), 3) soluble fiber (CB2) fraction and α-helix and β-sheet height ratio (r = -0.63, P < 0.001), and 4) unavailable NDF (CC) fraction and height of amide I (r = 0.55, P = 0.002). These results indicated feed molecular structure spectral properties of the oil-seeds and co-products related to CNCPS protein and carbohydrate degradation fractions in ruminant systems.

Application of FT/IR-ATR vibrational spectroscopy to reveal protein molecular structure of feedstock and co-products from Canadian and Chinese canola processing in relation to microorganism bio-degradation and enzyme bio-digestion

The principal objective of this study was to apply FT/IR-ATR vibrational spectroscopy to inspect the relationship between rumen dry matter (DM) and protein degradation, rumen undegraded protein (RUP) intestinal digestion and processing induced protein molecular structure changes in feedstock (canola oil seeds) and co-products (canola meal) from bio-oil processing from different crushing plants in Canada and China. The rumen DM and protein degradation, rumen undegraded protein intestinal digestion and protein molecular structure affected by bio-oil processing were examined using in situ, three step in vitro digestion and Fourier transform infrared (FT/IR) molecular spectroscopy techniques, respectively. The results showed that the protein molecular structure; α-helix height and α-helix to β-sheet height ratio had a close association with rumen DM and protein degradation and rumen undegraded protein intestinal digestibility. Multiple regression analyses showed that protein β-sheet height and α-helix to β-sheet height ratio spectral intensity can be used to predict rumen DM and protein degradation, while intestinal digestibility of rumen undegraded protein can be predicted by α-helix height and β-sheet height. In conclusion, the co-product canola meal from bio-oil processing is a good source of intestinally digestible protein. Rumen DM and protein degradation and intestinal digestibility of rumen undegraded protein are related to the protein molecular structures of the co-products affected by changes during bio-oil processing.

Determine effect of pressure heating on carbohydrate related molecular structures in association with carbohydrate metabolic profiles of cool-climate chickpeas using Globar spectroscopy

Grain has been heat-processed to alter rumen degradation characteristics and improve nutrient availabilities for ruminants. However, limited study was found on internal structure changes induced by processing on a molecular basis. The objectives of this study were to use advanced vibrational molecular spectroscopy to: (1) determine the processing induced carbohydrate (CHO) structure changes on a molecular basis, (2) investigate the effect of pressure heating on changes of CHO chemical profiles, CHO subfractions in cool-climate CDC Chickpea varieties, and (3) to reveal the association between carbohydrates related molecular spectra with carbohydrate metabolic profiles. The cool-climate CDC chickpea varieties with multisource were pressure heated in an autoclave at 120 °C for 60 min; and FTIR vibrational spectroscopy was used to detect the molecular spectra. Molecular spectroscopic results showed that compared to raw chickpea varieties, autoclave heating induced changes in both total CHO (region and baseline ca. 1186-946 cm^-1) and structural CHO (STCHO, region and baseline ca. 1482-1186 cm^-1), except for cellulosic compounds (CELC, region and baseline ca. 1374-1212 cm^-1). The CHO chemical profile and rumen degradation results showed that autoclave heating decreased rumen degradable, undegradable and intestinal digestible sugar (CA4) content, but increased available fiber (CB3) content, without affecting available energy of chickpeas. The changes of CHO molecular spectra in chickpea varieties were strongly correlated with CHO chemical profiles, CHO subfractions, and CHO rumen degradation characteristics. Moreover, the regression analysis showed that STCHO peak 1 height could be used to predict sugar content, its rumen degradability and digestibility of chickpeas. Our results suggest that autoclave heating markedly changes sugar and fiber degradation characteristics. The carbohydrate molecular spectral profiles are associated with carbohydrate metabolic profiles in raw and pressure heated cool-climate chickpeas.

Effects of Heat Treatment of Green Protein on in Situ Protein Disappearance and in Vitro Fatty Acid Biohydrogenation

Soluble protein extracted from leaves and stems of grasses and forage legumes is defined as green protein. The present study was conducted to evaluate in situ green protein degradability, intestinal protein disappearance, and in vitro fatty acids biohydrogenation (BH) in dairy cows. Three green protein concentrates (red clover, ryegrass, and grass clover) were heat treated as follows: oven-drying at 70 °C, subsequent autoclaving at 121 °C for 45 min, and for grass clover also spin flash-drying. Freeze-dried green protein was considered as a control (untreated). Autoclaving and oven-drying of green protein reduced the crude protein and dry matter degradability. The linolenic acid BH rate was lowest in heat-treated grass clover concentrate ( P < 0.01). In conclusion, green proteins are heat sensitive, and oven-drying can be an appropriate method to increase the amount of protein and unsaturated fatty acids escaping from the rumen.

Alteration of biomacromolecule in corn by steam flaking in relation to biodegradation kinetics in ruminant, revealed with vibrational molecular spectroscopy

Large scale of steam flaked corn has been used in dairy ration to maintain high milk production level. This study aimed to determine effects of steam flaking on processing-induced intrinsic molecular structure changes that were associated with rumen degradation kinetics and nutrients supply. The advanced vibrational molecular spectroscopy was applied to reveal the processing-induced intrinsic structure changes on a molecular basis. The rumen degradation kinetics and nutrient supply were determined using in situ approach in ruminant livestock system. Raw corn grain (RC) and steam flaked corn grain (SFC) were obtained from two different processing plants. The results showed that (1) Compared to RC, SFC had greater truly digestible non-fiber carbohydrate [tdNFC: 86.8 versus 78.0% dry matter (DM)], but lower truly digestible crude protein [tdCP: 7.7 versus 9.0% DM]. (2) The steam flaking increased (P<0.01) rumen degradable DM (RDDM) and starch (RDSt), but decreased (P<0.01) rumen degradable protein (RDP). (3) Molecular absorbance intensities of most carbohydrate biopolymers were greater in SFC (P<0.01), but protein amides associated molecular spectral intensities were lower (P<0.01) in SFC. (4). The molecular structure and nutrient interactive study showed that carbohydrate spectral intensities were positively (P<0.10) associated with RDDM and RDSt and protein amide spectral intensities were positively (P<0.10) associated with RDP. This results indicated that the steam flaking induced molecular structure changes had an interactive relationship with rumen degradation kinetics.

Physicochemical characteristics, ATR-FTIR molecular interactions and in vitro starch and protein digestion of thermally-treated whole pulse flours

Hydrothermal treatments, annealing (ANN) and heat moisture treatment (HMT) were applied to four whole pulse flours (black bean, broad bean, chickpea and lentil) with the aim to increase their slow digestible (SDS) and resistant starch (RS) fractions. In order to assess differences in their molecular interactions, they were analyzed and compared by ATR-FTIR before and after in vitro digestion. Both hydrothermal treatments promoted changes on starch granular architecture, being reflected on their thermal and pasting properties, that where positively correlated with their amylose and protein contents (R=0.96, P<0.01). Overall, the proposed hydrothermal treatments increased their SDS and RS fractions, but they had different effect on their in vitro protein digestion. The ATR-FTIR analysis of cooked flours before and after digestion showed that thermal treatments promoted new physical interactions at molecular scale between starch and proteins, that were correlated with the amount of RS fraction. The outcomes of this study could help to understand the slow digestion properties and possible interactions of the flour components in these four pulses.

Gene-Transformation-Induced Changes in Chemical Functional Group Features and Molecular Structure Conformation in Alfalfa Plants Co-Expressing Lc-bHLH and C1-MYB Transcriptive Flavanoid Regulatory Genes: Effects of Single-Gene and Two-Gene Insertion

Alfalfa (Medicago sativa L.) genotypes transformed with Lc-bHLH and Lc transcription genes were developed with the intention of stimulating proanthocyanidin synthesis in the aerial parts of the plant. To our knowledge, there are no studies on the effect of single-gene and two-gene transformation on chemical functional groups and molecular structure changes in these plants. The objective of this study was to use advanced molecular spectroscopy with multivariate chemometrics to determine chemical functional group intensity and molecular structure changes in alfalfa plants when co-expressing Lc-bHLH and C1-MYB transcriptive flavanoid regulatory genes in comparison with non-transgenic (NT) and AC Grazeland (ACGL) genotypes. The results showed that compared to NT genotype, the presence of double genes (Lc and C1) increased ratios of both the area and peak height of protein structural Amide I/II and the height ratio of α-helix to β-sheet. In carbohydrate-related spectral analysis, the double gene-transformed alfalfa genotypes exhibited lower peak heights at 1370, 1240, 1153, and 1020 cm⁻¹ compared to the NT genotype. Furthermore, the effect of double gene transformation on carbohydrate molecular structure was clearly revealed in the principal component analysis of the spectra. In conclusion, single or double transformation of Lc and C1 genes resulted in changing functional groups and molecular structure related to proteins and carbohydrates compared to the NT alfalfa genotype. The current study provided molecular structural information on the transgenic alfalfa plants and provided an insight into the impact of transgenes on protein and carbohydrate properties and their molecular structure’s changes.

Structural changes on a molecular basis of canola meal by conditioning temperature and time during pelleting process in relation to physiochemical (energy and protein) properties relevant to ruminants

The objectives of this study were: (1) To investigate the effects of conditioning temperature (70, 80, 90°C), time (30, 60 sec), and interaction (temperature × time) during the pelleting process on internal protein molecular structure changes of the co-products; (2) To identify differences in protein molecular structures among pellets that were processed under different conditions, and between unprocessed mash and pellets; 3) To quantify protein molecular structure changes in relation to predicted energy and protein utilization in dairy cows. The final goal of this program was to show how processing conditions changed internal feed structure on a molecular basis and how molecular structure changes induced by feed processing affected feed milk value in dairy cows. The hypothesis in this study was that processing-induced protein inherent structure changes affected energy and protein availability in dairy cattle and the sensitivity and response of protein internal structure to the different pelleting process conditions could be detected by advanced molecular spectroscopy. The protein molecular structures, amides I and II, amide I to II ratios, α-helix structure, β-sheet structure, and α to β structure ratios, were determined using the advanced vibrational molecular spectroscopy (ATR-FT/IR). The energy values were determined using NRC2001 summary approach in terms of total digestible nutrients, metabolizable and net energy for lactation. The protein and carbohydrate subfactions that are related to rumen degradation characteristics and rumen undegraded protein supply were determined using updated CNCPS system. The experiment design was a RCBD and the treatment design was a 3x2 factorial design. The results showed that pelleting induced changes in protein molecular structure. The sensitivity and response of protein inherent structure to the pelleting depended on the conditioning temperature and time. The protein molecular structure changes were correlated (P < 0.05) with energy values and protein subfractions of the pelleted co-product. The results indicated that the protein internal molecular structure had significant roles in determining energy and protein nutritive values in dairy cows. Multi-regression study with model variables selection showed that the energy and protein profiles in pelleted co-products could be predicted with the protein molecular structure profiles. This approach provides us a relatively new way to estimate protein value in dairy cows based on internal protein molecular structure profile.

The Use of Gene Modification and Advanced Molecular Structure Analyses towards Improving Alfalfa Forage

Alfalfa is one of the most important legume forage crops in the world. In spite of its agronomic and nutritive advantages, alfalfa has some limitations in the usage of pasture forage and hay supplement. High rapid degradation of protein in alfalfa poses a risk of rumen bloat to ruminants which could cause huge economic losses for farmers. Coupled with the relatively high lignin content, which impedes the degradation of carbohydrate in rumen, alfalfa has unbalanced and asynchronous degradation ratio of nitrogen to carbohydrate (N/CHO) in rumen. Genetic engineering approaches have been used to manipulate the expression of genes involved in important metabolic pathways for the purpose of improving the nutritive value, forage yield, and the ability to resist abiotic stress. Such gene modification could bring molecular structural changes in alfalfa that are detectable by advanced structural analytical techniques. These structural analyses have been employed in assessing alfalfa forage characteristics, allowing for rapid, convenient and cost-effective analysis of alfalfa forage quality. In this article, we review two major obstacles facing alfalfa utilization, namely poor protein utilization and relatively high lignin content, and highlight genetic studies that were performed to overcome these drawbacks, as well as to introduce other improvements to alfalfa quality. We also review the use of advanced molecular structural analysis in the assessment of alfalfa forage for its potential usage in quality selection in alfalfa breeding.

Univariate and multi-variate comparisons of protein and carbohydrate molecular structural conformations and their associations with nutritive factors in typical by-products

BACKGROUND

Little attention has been paid on the inherent molecular structural effects among agricultural by-products. In this study, soybean meal (SM), wheat bran (WB), corn distillers dried grains with soluble (DDGS), dry brewer's grain (DBG), wet brewer's grain (WBG), and apple pomace (AP), which are widely used in the animal industry were selected to explore protein and carbohydrate molecular structural conformations.

RESULTS

All the protein peak heights (including α-helix and β-sheet) and areas were exhibited highest values in SM and lowest in AP. The SM had the highest peak area intensity of cellulosic compounds (CELC), while the remaining varieties showed the lowest absorbance level. The TSCHO (sum of structural carbohydrate (SCHO) and CELC area exhibited variations among the samples. Multivariate comparisons showed AP had no molecular structural association with other by-products within the protein amide region. Protein amides I, II and (I+II) areas, α-helix, β-sheet and area ratio of protein amide and (TSCHO + TCHO) had strong relationships with CP, NDF, ADF, ADL, SCP, starch, PC, CA, CC and TDN contents.

CONCLUSION

Inherent molecular structures varied among the selected by-product types and they might be used as potential predictors of nutritive factors, especially for protein structural information. © 2016 Society of Chemical Industry.

Using vibrational infrared biomolecular spectroscopy to detect heat-induced changes of molecular structure in relation to nutrient availability of prairie whole oat grains on a molecular basis

Background

To our knowledge, there is little study on the interaction between nutrient availability and molecular structure changes induced by different processing methods in dairy cattle. The objective of this study was to investigate the effect of heat processing methods on interaction between nutrient availability and molecular structure in terms of functional groups that are related to protein and starch inherent structure of oat grains with two continued years and three replication of each year.

Method

The oat grains were kept as raw (control) or heated in an air-draft oven (dry roasting: DO) at 120 °C for 60 min and under microwave irradiation (MIO) for 6 min. The molecular structure features were revealed by vibrational infrared molecular spectroscopy.

Results

The results showed that rumen degradability of dry matter, protein and starch was significantly lower (P <0.05) for MIO compared to control and DO treatments. A higher protein α-helix to β-sheet and a lower amide I to starch area ratio were observed for MIO compared to DO and/or raw treatment. A negative correlation (−0.99, P < 0.01) was observed between α-helix or amide I to starch area ratio and dry matter. A positive correlation (0.99, P < 0.01) was found between protein β-sheet and crude protein.

Conclusion

The results reveal that oat grains are more sensitive to microwave irradiation than dry heating in terms of protein and starch molecular profile and nutrient availability in ruminants.

The Role of Proanthocyanidins Complex in Structure and Nutrition Interaction in Alfalfa Forage

Alfalfa (Medicago sativa L.) is one of the main forages grown in the world. Alfalfa is a winter hardy, drought tolerant, N-fixing legume with a good longevity, high yield, high nutrient levels, high digestibility, unique structural to non-structural components ratio, high dry matter intake, and high animal productivity per hectare. However, its main limitation is its excessively rapid initial rate of protein degradation in the rumen, which results in pasture bloat and inefficient use of protein with consequent excessive excretions of nitrogen into the environment. Proanthocyanidins are secondary plant metabolites that can bind with protein and thereby reduce the rate and extent of ruminal protein degradation. However, these secondary metabolites do not accumulate in alfalfa. This review aims to firstly describe the events involved in the rapid release of protein from alfalfa and its effect on ruminant nutrition, environmental pollution, and pasture bloat; secondly, to describe occurrence, structure, functions and benefits of moderate amounts of proanthocyanidin; and finally, to describe the development of alfalfa which accumulates moderate amounts of proanthocyanidins. The emphasis of this review focuses on the role of proanthocyanidins compounds in structure and nutrition interaction in ruminant livestock systems.

Molecular basis of processing-induced changes in protein structure in relation to intestinal digestion in yellow and green type pea (Pisum sativum L.): A molecular spectroscopic analysis

The objectives of this study were (1) to quantify the protein inherent molecular structural features of green cotyledon (CDC Striker) and yellow cotyledon (CDC Meadow) pea (Pisum sativum L.) seeds using molecular spectroscopic technique (FT/IR-ATR); (2) measure the denaturation of protein molecular makeup in the two types of pea during dry roasting (120°C for 60 min), autoclaving (120°C for 60 min) or microwaving (for 5 min); and (3) correlate the heat-induced changes in protein molecular makeup to the corresponding changes in protein digestibility determined using modified three-step in vitro procedure. Compared with yellow-type, the green-type peas had higher (P<0.05) ratios of amide I to II peak height (1.698 vs. 1.805) and area (1.843 vs. 2.017). A significant correlation was observed between the amide I and II peak height (r=0.48) and peak area (r=-0.42) ratio with protein content. Compared with yellow-type, the green-type peas had lower (P<0.05) α-helix:β-sheet ratio (1.015 vs. 0.926), indicating varietal difference in protein secondary structure makeup. All processing applications increased α-helix:β-sheet ratio, with the largest (P<0.05) increase being observed with roasting and microwaving. The heat-induced changes in α-helix:β-sheet ratio was strongly correlated to intestinal digestibility of protein within the green (r=-0. 86) and yellow (r=0.81) pea-types. However, across the pea types the correlation was not significant. Principal component and hierarchical cluster analyses on the entire spectral data from the amide region (ca. 1727-1480 cm(-1)) were able to visualize and discriminate the structural difference between pea varieties and processing treatments. This study shows that the molecular spectroscopy can be used as a rapid tool to screen the protein value of raw and heat-treated peas.

Relationship between Molecular Structure Characteristics of Feed Proteins and Protein In vitro Digestibility and Solubility

The nutritional value of feed proteins and their utilization by livestock are related not only to the chemical composition but also to the structure of feed proteins, but few studies thus far have investigated the relationship between the structure of feed proteins and their solubility as well as digestibility in monogastric animals. To address this question we analyzed soybean meal, fish meal, corn distiller’s dried grains with solubles, corn gluten meal, and feather meal by Fourier transform infrared (FTIR) spectroscopy to determine the protein molecular spectral band characteristics for amides I and II as well as α-helices and β-sheets and their ratios. Protein solubility and in vitro digestibility were measured with the Kjeldahl method using 0.2% KOH solution and the pepsin-pancreatin two-step enzymatic method, respectively. We found that all measured spectral band intensities (height and area) of feed proteins were correlated with their the in vitro digestibility and solubility (p≤0.003); moreover, the relatively quantitative amounts of α-helices, random coils, and α-helix to β-sheet ratio in protein secondary structures were positively correlated with protein in vitro digestibility and solubility (p≤0.004). On the other hand, the percentage of β-sheet structures was negatively correlated with protein in vitro digestibility (p<0.001) and solubility (p = 0.002). These results demonstrate that the molecular structure characteristics of feed proteins are closely related to their in vitro digestibility at 28 h and solubility. Furthermore, the α-helix-to-β-sheet ratio can be used to predict the nutritional value of feed proteins.