In vitro unfermented fiber is a good predictor of the digestible and metabolizable energy content of corn distillers dried grains with solubles in growing pigs

Authors: ZENG, ZHIKAI - University Of Minnesota; JANG, JAE CHEOL - University Of Minnesota; Kerr, Brian; SHURSON, GERALD - University Of Minnesota; URRIOLA, PEDRO - University Of Minnesota

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2019
Publication Date: 7/1/2019
Citation: Zeng, Z., Jang, J., Kerr, B.J., Shurson, G., Urriola, P. 2019. In vitro unfermented fiber is a good predictor of the digestible and metabolizable energy content of corn distillers dried grains with solubles in growing pigs. Journal of Animal Science. 97(8):3460-3471. https://doi.org/10.1093/jas/skz221.
DOI: https://doi.org/10.1093/jas/skz221

Interpretive Summary: Corn dried distillers grains with solubles (DDGS) has been widely used to partially replace a portion of corn and soybean meal in swine diets because it is a cost-competitive source of digestible energy. Dietary fiber in corn-DDGS is composed of multiple carbohydrates with distinct properties, some of which can be digested in the small intestine. These undigested carbohydrates may, however, be fermented in the large intestine to produce short-chain fatty acids which can contribute digestible energy to the pig. The objective of the current study was to determine the in vitro fermented and unfermented neutral detergent fiber content of various DDGS sources to determine their relative contributions for predicting the digestible energy content of DDGS. Data from this experiment indicate that in vitro unfermented fiber is strongly negatively associated with energy and neutral detergent fiber digestibility, and therefore, is a good predictor of the digestible energy in DDGS. This information is important for nutritionists at universities, feed companies, and swine production facilities for estimated energy value of reduced DDGS for use in feed formulations, and provides a basis from which to assess its economic value.

Technical Abstract: Characterizing fiber into fermentable and unfermentable fractions may enhance the accuracy of estimating digestible (DE) and metabolizable (ME) energy content in fiber-rich ingredients. Therefore, the objective of the study was to analyze the concentrations of neutral detergent fiber (NDF), representing both the fermentable (fNDFom) and unfermentable (uNDFom) portions among sources of corn distillers dried grains with solubles (DDGS), and determine their relative contributions to DE and ME content. The concentrations of DE and ME, as well as apparent total tract digestibility (ATTD) of gross energy (GE), were measured in a previous experiment. Samples of DDGS (0.5 g) were mixed with fecal inoculum and incubated for 8, 12, and 72 h. The ash corrected NDF (NDFom) content of DDGS residues at each time point was determined. The fNDFom increased with fermentation time of 8 h (21.6%), 12 h (29.0%) and 72 h (68.6%). The ATTD of GE increased as the uniform decreased at 8 h (uNDFom8; R2 = 0.83; P < 0.01) and 72 h (uNDFom72; R2 = 0.83; P < 0.01). Likewise, ME content of DDGS increased as uNDFom72 decreased (R2 = 0.59; P < 0.01). The best fit DE equation was DE (kcal/kg DM) = 2,175 – 3.07 × uNDFom8 (g/kg, DM) – 1.50 × uNDFom72 (g/kg, DM) + 0.55 × GE (kcal/kg DM) [R2 = 0.94, SE = 36.21]. The best fit ME equation was ME (kcal/kg DM) = 1,643 – 2.31 × uNDFom8 (g/kg, DM) – 2.54 × uNDFom72 (g/kg, DM) + 0.65 × GE (kcal/kg DM) – 1.42 × crude protein (g/kg DM) [R2 = 0.94, SE = 39.21]. These results indicate that in vitro unfermented fiber is strongly negatively associated with GE and NDF digestibility, and therefore, is a good predictor of DM and ME content in corn-DDGS.