Silo Bag Storage

Storage of WDGS by itself in bags under pressure (300 psi or greater) can result in splitting bags (Figure 4). If splitting is going to occur, the problem usually occurs relatively soon after bagging (within a few days). Therefore, the objective of these storage tests was to add different feeds to allow for bagging under pressure with little risk of splitting the bags.

Different amounts, as well as types of forage or dry feeds, were evaluated by combining with WDGS. The WDGS in this test was 34% DM. Traditional WDGS were mixed using a truck mounted feed mixer with weighing capability. During all of the bagging experiments, the bagger was held at a constant pressure of 300 psi. All of the grass hay, wheat straw and corn stalks were ground through a tub grinder with a 5-inch screen; alfalfa hay was ground with a 7-inch screen. Feed products used in the experiments contained different DM, therefore all percentages are presented on a DM basis.

WDGS (34% DM) were mixed with one of five different feedstuffs, including grass hay, alfalfa hay, wheat straw, DDGS and WCGF. During the experiment, adjustments were made based on how the different products bagged. Grass hay was tested at 17.5, 15, 12.5, 10 and 7.5% with the remaining percentages in each case being WDGS on a DM basis. Alfalfa hay was tested at 25, 22.5, 20, 17.5 and 15% on a DM basis with increasing percentages of WDGS. Wheat straw was mixed with WDGS at 15% and 12.5% (DM basis). Ratios of DDGS:WDGS evaluated were 50:50 and 60:40 (DM basis). WCGF was mixed with WDGS at ratios of 40:60 and 50:50, respectively (DM basis). Figure 5 depicts some of the different mixtures performed during bagging. Figure 5 illustrates that we did not provide enough forage or bulk in some cases.

To determine the amount of feeds to weigh out, producers need to accurately account for the mixture needed on a DM basis, and then calculate the as-is percentages so that feeds can be weighed out. This process is similar to combining feeds at the time of feeding into mixing equipment. With wetter feeds such as WDGS, the as-is percent inclusion of forage is significantly less than the mixture on a DM basis. Table 1 provides example calculations for determining the mixture on an as-is basis from the mixture provided on a DM basis, along with the DM of each ingredient.

The minimum amounts of forage needed for bagging under pressure are likely dictated by the fiber content of the forage. It appears that forages are the best choice to add bulk and allow for bagging under pressure. Lower quality forages (i.e., more fibrous or greater neutral detergent fiber [NDF] content) such as wheat straw and corn stalks are probably better suited for this storage method than more digestible, higher quality forages. Forage sources can likely be exchanged on an equal fiber basis, but this has not been well established given the difficulty researching all the possible combinations of WDGS and forages available.

Interestingly, it does not require a great deal of forage to add enough bulk to keep bags from splitting when bagged under pressure. Our data would suggest that minimum amounts of wheat straw (and presumably corn stalks) are a mixture of 12.5% wheat straw with 87.5% WDGS (DM basis). On an as-is basis, this equates to approximately 5% straw. However, the percentages on an as-is basis are dependent on the DM or moisture content of both the straw and the WDGS. Grass hay is less fibrous than either wheat straw or corn stalks and, as a result, more grass hay is needed when mixed with WDGS. Our recommendation for combining grass hay and WDGS is to mix 15% (only 6-6.5% on an as-is basis) grass hay with 85% WDGS. Bags did split when the 7.5% and 10% grass hay mixtures were used. More alfalfa is required than any other forage tested. However, alfalfa is an unlikely forage source to be used due to cost and quality. If alfalfa was used, then the appropriate mixture would be 22.5% alfalfa with 78.5% WDGS (DM basis). Based on our studies, Table 1 provides the minimum mixtures required for grass hay, alfalfa hay, wheat straw, DDGS and WCGF when combined with WDGS.

We would recommend lower quality forages such as low-quality hays, straws or stalks, as they require lower amounts to be mixed with WDGS, are usually less expensive, and may be a good use for these low-quality forages compared to high-quality forage. In many cases, this "mixture" of forage and WDGS may serve as the entire roughage source for feedlots to use in their finishing rations.

It is not clear whether mixing low-quality forages with WDGS actually improves the palatability and/or digestibility of the forage when fed to cattle. To test this, we have conducted feeding experiments and are in the process of comparing "stored" forage and WDGS combinations compared to feeding a similar mixture of WDGS and forages "fresh" daily.

For cow-calf producers that want to combine low-quality forages with WDGS to maintain a herd or to enhance the low-quality forage, perhaps determining the minimum amount of forage needed to bag WDGS is not the goal. In their situation, increasing the amount of forage may be more beneficial if it allows for storage of low quality forages and a mechanism to feed these forages to beef cows or growing cattle.

We have bagged mixtures of 67% wheat straw with 33% WDGS, 33% wheat straw with 67% WDGS, and a 50:50 blend of corn stalks and WDGS (DM basis). We have also stored a mixture of 56% grass hay with 44% WDGS in a Nebraska Sandhills ranch setting (Figure 6). The WDGS was dumped on the ground in a meadow and was easily picked up by equipment. In all cases, storage was possible and little to no spoilage was visually observed. However, with greater amounts of dry, low-quality forage, one challenge may be insufficient moisture to allow for compaction in the bag and to exclude all the air. If the mixture is too dry, then some air may be "trapped" even in a bag that was compacted under pressure. It is not clear what minimum amount of moisture is required to ensure enough moisture to adequately compact the mixture in the bag and/or prevent spoilage.

More recently, we have bagged 25% solubles with 75% wheat straw, but increased the moisture (or decreased the DM) to 50%. Similar storage worked well with 45% solubles and 55% straw, 25% WDGS with 75% straw, and 55% WDGS with 45% straw (DM basis). The solubles at either 25% or 45% and the WDGS at 25% mixtures were all increased to 50% moisture by adding water (or decreased to 50% DM) and stored in a bag with no spoilage or compacting problems observed. We would estimate that mixtures of less than 35-40% moisture are more risky in terms of spoilage during storage in a bag. This risk is likely greater in bunker storage facilities, as will be discussed, compared to bags.

For more information or to request additional copies of this manual, contact the Nebraska Corn Board at 1-800-632-6761 or e-mail kelly.brunkhorst@nebraska.gov

Download PDF version of this manual, or

Date published: May, 2008