Allowing wet distillers grains plus solubles (WDGS) to spoil in the bunker during storage doesn’t affect growing cattle or feedlot cattle performance but will result in increased shrink and nutrient losses.
Open bunkers are the most common method of storing WDGS. Spoilage generally begins within a few days at the surface of the storage pile and is greater in summer than winter. The threat of spoilage often makes it impractical for smaller feeders, who can’t utilize enough WDGS within a few days of purchase to take delivery of semitruck loads of WDGS.
University of Nebraska researchers studied the effects of WDGS spoilage on nutrient loss and cattle performance by storing split-load semitruck loads of WDGS in either uncovered bunkers (allowed to spoil) or in sealed silo bags (unspoiled). A winter study was conducted with growing steers where WDGS was stored for five months prior to the onset of feeding in March, while a summer study was conducted with finishing steers where WDGS was stored for 38 days prior to the onset of feeding in July.
Samples of both spoiled and unspoiled WDGS were collected daily after each source was allowed to mix in the feed truck prior to the addition of other ration ingredients. These samples were composited and analyzed weekly for nutrient content and mycotoxins. No measurable amounts of mycotoxins were detected.
Growing steers (730 lbs.) were fed diets containing either 15% or 40% unspoiled or spoiled WDGS in an 84-day study. The remaining ration ingredients were grass hay and 3%-4% supplement. As expected, steers fed the 40% WDGS rations had better performance than steers fed 15% WDGS rations.
The effect of feeding spoiled WDGS was the same for both WDGS inclusion levels. Dry matter (DM) intake was greater (17.8 vs. 16.3 lbs./day) for steers fed the unspoiled WDGS, but average daily gain (ADG) and feed efficiency were not affected by feeding the spoiled WDGS (1.01 vs. 0.93 lbs./day and 19.2 vs. 19.6, respectively, for unspoiled and spoiled).
Finishing steers (878 lbs.) were fed unspoiled or spoiled WDGS at 40% of the ration DM. Dry-rolled corn (47.5%), alfalfa hay (7.5%), and supplement (5.0%) made up the remainder of the rations. A third treatment containing no WDGS consisted of dry-rolled corn (82.5%), alfalfa hay (7.5%), and supplement (5.0%). The steers were on feed for 130 days.
DM intake (21.7 vs. 22.4 lbs./day), ADG (2.95 vs. 3.18 lbs./day) and feed:gain (7.4 vs. 7.1) were not different between unspoiled and spoiled WDGS, respectively. Hot carcass weight, ribeye area, fat thickness, marbling score and yield grade were also unaffected by feeding spoiled WDGS. Cattle fed both WDGS rations outperformed the non-WDGS steers with 17% faster daily gain, 15% more efficient gain and 44-lb. heavier carcass weights.
In both experiments, on average, 7% of the WDGS stored in the uncovered bunkers was determined to be spoiled. Spoilage resulted in DM loss (shrinkage) of 6.0% and 12.3%, neutral detergent fiber loss of 10.3% and 8.0%, and crude protein loss of 4.9% and 12.2% of the initial WDGS stored, during the winter and summer months, respectively. Fat loss during the summer was 16.0%. Surprisingly, the nutrient loss didn’t affect cattle performance.
Smaller livestock operations can purchase semitruck loads of WDGS and store the product in bunkers without fear of cattle performance loss, but will encounter greater storage loss over time resulting in higher feeding costs. ❚❚
Scott B. Laudert, Ph.D., is a beef cattle technical consultant and former Kansas State University Extension livestock specialist based in Woodland Park, CO. He can be reached at 719-660-4473.