#17-036

Progress

Date Full Report Received

08/01/2018

Date Abstract Report Received

08/01/2018

Investigation

Institution:
Primary Investigator:

The aims of this project were 1) to develop a new method for quantification of the feeding value of corn DDGS, and 2) to increase extraction of nutrients from corn DDGS (a low energy feedstuffs). We used an in vitro digestibility assay that was developed in NPB project #13-014. We introduced modifications to the procedure that allowed us to understand what the characteristics of fiber are that are responsible for low digestible and metabolizable energy (DE and ME) in DDGS. We used 15 sources of DDGS of known DE and ME and that we have preserved at – 20 °C (NPB project #11-136). We measured fermentability of neutral detergent fiber (NDF) after incubating DDGS with fecal inocula for 8, 12, and 72 hours. We observed that a significant portion of NDF (21.6%) was degraded after 8 hours of incubation; while it took another 72 hours to degrade 68% of NDF. In addition, the lower content of undigestible fiber in DDGS (uNDFom8), the greater apparent total tract digestibility (ATTD) of gross energy (R2 = 0.881) and ether extract (R2 = 0.382). These two characteristics of fNDFom8 made it a good predictor of the DE (R2 = 0.93) and ME (R2 = 0.92) content among the 15 sources of DDGS. Subsequently, we used x-ray diffraction to determine the relationship between crystalline configuration of fiber in DDGS and ATTD of NDF. We observed that DDGS with low (44.5%) ATTD of NDF had lower crystallinity index (9.2%) than 12.2% in DDGS with high ATTD of NDF (57.3%). These observations suggest that the differences in digestibility of fiber among sources of DDGS appears to be related to crystalline configuration of fiber. This crystalline structure is more resistant to degradation in the large intestine of pigs. Therefore, for the second objective we used ammonia fiber expansion (AFEX) to degrade the unfermentable portion of fiber in DDGS from two sources (A and B). We measured in vitro digestibility of dry matter and energy during fermentation of the non-treated and treated DDGS with and without enzymes. We observed that pretreatment of DDGS increased the digestibility of dry matter and energy, it also increased in vitro DE from 3,579 to 4,502 kcal/kg DM in DDGS A and from 3,699 to 4,225 kcal/kg DM. The effect of adding enzymes was negligible compared with AFEX.

Key observations of this research:
1) Digestibility of fiber differs among sources of corn DDGS and the difference in digestibility of fiber appears to be due to crystalline configuration of fiber.
2) The greater content of undigestible fiber in DDGS, the less digestibility of gross energy, protein, and lipids. Consequently, the greater content of undigestible fiber in DDGS, the less DE and ME in DDGS.
3) Ammonia expansion is an effective technology for increasing the energy value in corn DDGS