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Concentration of the non-starch polysaccharide 1,3 β-glucan and α-mannan protein in corn derived distillers grains with solubles
Feedstuffs for swine nutrition such as the by-product of ethanol production, corn distillers drains with solubles (DDGS), contain a variety of non-starch polysaccharides (NSP) including 1,3 β-glucan (BG) and the α-mannan (AM) component of glycoproteins. The BG and AM in the DDGS are primarily contributed by the cell walls from Saccharomyces cerevisiae used in the corn-based ethanol fermentation process. Furthermore, both BG and AM are recognized as biological modifiers that are resistant to enzymes produced endogenously in the gastrointestinal tract of the pig and are anti-nutritive components in the diet. The objective of the study was to determine the concentration of BG and AM in cohort-split samples of the cereal grain by-product DDGS, and to develop an estimate model to predict the results based on the crude protein content of DDGS. Crude protein, moisture, crude fat, crude fiber (28.10%, 15%, 10.04%, 6.45%; respectively) of the composite sample were previously determined using wet chemistry procedures from a commercial laboratory. Amino acid concentrations including lysine, isoleucine, leucine, methionine, threonine, valine, alanine, aspartic acid, cysteine, glutamic acid, glycine, and proline were also determined. A composite sample from 40 serial samples in a 25 ton lot was split into twenty samples of equal weight. The BG concentration was estimated using an enzymatic kit (K-EBHLG 03/13 Enzymatic Yeast Beta-glucan) from Megazyme (Megazyme International Ireland Limited, Bray, Ireland). Quantitative determination of the monosaccharides galactose and mannose in the samples were also determined by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) before and after hydrolysis with hydrochloric acid (Eurofins Scientific, Inc. Analytical Laboratory Amsterdam, The Netherlands). The BG and AM concentrations ranged from 1.875 to 2.234% with a mean average of 2.072 w/w% (SD=0.108) and 0.88 to 1.12% with a mean average of 1.018 w/w% (SD=0.039), respectively. Comparison of the results to known cell wall architecture in S. cerevisiaeallowed testing the possibility of using the protein content in DDGS to estimate the BG and AM concentrations by calculation. Results of this experiment would slightly overstate the BG contribution in comparison to known results for cell wall architecture allowing the concept of estimating by difference in protein contribution to slightly underestimate known values. A better knowledge of BG and AM concentrations in DGGS lots readily obtained through routine or calculated methods may provide an opportunity to improve pig performance through understanding their concentrations and the potential anti-nutritive impact of these highly reactive biological modifiers.
Keywords: NSP, 1,3 β-glucan, α-mannan