Processing of wet distiller\u27s grains to optimize protein quality for ruminants

The main hypothesis of this thesis was that as the residence temperature and time in the rotary drum increase, a more heat-damaged dried distiller’s grains product will be produced and more intestinally unavailable to the ruminant. The secondary hypothesis was that as the amount of dried distiller’s grains with solubles (DDGS) increased in the ration, there would be a decrease in feedlot lamb performance and carcass characteristics, and an increase in linoleic acid biohydrogenation intermediates in the LM and s.c. adipose tissue of feedlot lambs. Wet distiller’s grains (WDG) samples were collected from three Midwestern ethanol plants and were dried in a mini-scale rotary dryer at varying temperature/time combinations to mimic the drying process in the ethanol plant. Optimal residence temperature and time was highly dependent on the WDG samples that were obtained from the three Midwestern plants. The rumen degradable protein, intestinally degradable protein, and intestinally undegradable protein varied between plants and was mainly affected in Plants 1 and 2. When DDGS were added to feedlot lamb rations at 50% on a DM basis, there were no negative effects on lamb performance or carcass characteristics. However, DMI was tended to be lower for the lambs fed diets with added crude CP compared with the control diet. Although G:F was not significant, the 50DDGS lambs had the greatest numerical efficiency. Total fatty acid content of both LM and s.c. adipose tissues were not altered due to increased amounts of DDGS in the ration. However, linoleic acid biohydrogenation intermediates were increased in the s.c. adipose tissue of lambs fed diets with added crude fat. In conclusion, optimal residence temperature and time in the rotary drum is highly variable between plants and further research needs to done to determine if the optimal combinations this research is applicable on a large scale. Dried distiller’s grains with solubles can be added to feedlot lamb rations without having a negative impact on performance, carcass characteristics, and fatty acid profiles. However, more research needs to be conducted to determine the maximum inclusion level of DDGS in feedlot lamb rations