As we head into silage season, take time to prepare for success. The strange spring has given many a rocky start, but careful planning and testing can improve results. From moisture and starch content to particle size and cutting date, we've got you covered. Here are six strategies to ensure silage success:
Methods to Determine the Energy Content of Silage
Methods used to evaluate corn silage quality include chemical methods such as fiber analysis; biological methods such as fermentation with ruminal microbes; and instrumental methods such as near-infrared reflectance spectroscopy (NIRS), which predicts nutrients rather than measuring them directly. All methods require representative samples and must be obtained from the silo, and the samples must be handled properly prior to analysis, including using the following methods:
- Corn silage samples should be sealed in a plastic bag and sent to a laboratory as soon as possible to reduce spoilage.
- Care should be taken to avoid exposure of the sample to high temperatures.
- Samples of fresh forage taken when the silo is being filled must be dried immediately to reduce losses due to respiration of sugars, which can dramatically increase the concentration of the remaining nutrients.
- Do not freeze samples, as the fiber content becomes artificially increased during thawing due to the condensation of soluble protein with other compounds.
Water Content Key in Making Corn Silage
Corn should be harvested for silage at a moisture content of 65 to 70 percent when using a horizontal bunker. If too wet - above 70 percent - yield potential is reduced and seepage will occur, resulting in the undesirable presence of clostridia bacteria fermentation. Researchers tested standing corn, including the cob, for moisture content Aug. 15 at the NDSU Central Grasslands Research Extension Center near Streeter, N.D. Here is what they found:
- Corn with the entire plant still green, tasseled and having two cobs in the R2 kernel stage (early kernel, no denting and no milk) was at 77.4 percent water content.
- Drought-stressed corn with the bottom three to four leaves that were brown tested at 76.5 percent water content. The plants had one cob in the R2 kernel stage.
- Drought-stressed corn with the bottom four to seven leaves that had turned brown and no cobs had a water content of 67.9 percent.
Variation in Starch Content can Determine Corn Silage Quality
Using wet chemistry and the same lab, test corn silage at three time points throughout the year, which include NDF, NDF digestibility (30 hours), starch and seven-hour starch digestibility. Record this key information, including the storage structure and hybrid. These steps can ensure success:
- Send out samples after having fermented four to six weeks, six to seven months and nine to eleven months.
- Keep a record of dry matter percentage, NDF, NDFD, starch, starch digestibility, storage structure and hybrid.
- Make notes related to ration changes, milk production and components associated with the corn silage analysis.
- Discuss corn silage quality and animal performance as necessary with the advisory team or appropriate consultants.
Corn Silage Refresher Part 1: How to Set Your Cutting Date
Dry matter (DM) or moisture content should be the main determinant that drives your decision of when to cut. The general recommendation by Michigan State University Extension is to aim for a window between 32 to 35 percent DM (68 to 65 percent moisture). However, other university research recommends that the optimal value could change depending on the structure being used to store the silage.
The recommendation for bunks and drive-over-piles is to harvest between 30 to 35 percent DM (70 to 65 percent moisture) thus, aiming for 33 percent. The amount of moisture is extremely important to obtain a dense packing of the corn silage which excludes air to allow proper fermentation. If your harvest will be stored in bags or upright silos, MSU Extension recommends that corn silage is harvested between 35 to 39 percent DM (65 to 60 percent moisture). Bags and uprights allow for additional dry matter to be harvested because the techniques used for packing are different thus allowing harvest to be executed with a lower moisture content. Silage harvested at higher-than-prescribed moisture levels can produce substantially more leachate resulting in other negative consequences.
Corn Silage Refresher Part 2: Analyzing and Adjusting During Harvest
Particle size can be analyzed by a laboratory, or for quicker results, on the field using a forage particle separator (see particle size guidelines). Multiple approaches can be used to track kernel processing. Performing this analysis will allow for adjustments that can optimize silage quality. A quick qualitative analysis can be performed on the field using a 32 ounce cup. Fill the cup with chopped forage (corn silage) then spread the sample over a clean surface. Browse through the entire sample and record the number of half kernels or larger. Pay special attention to the number of whole or nicked kernels. If using this analysis, the goal is to find less than two half or whole kernels per sample (32 ounces). A more standardized process is the corn silage processing score or CSPS. It's important to remember that starch concentration is one of the important reasons to feed corn silage thus ensuring starch availability is key.
Assessing Silage Quality through Sensory Evaluation
One can gain significant insight as to the quality of silage, corn or hay-crop, by its smell, sight and feel. Sensory evaluation may suggest the need for further chemical or physical characterization of the feed should a problem be identified. Sensory evaluation of silage would include the following:
- Observe the contour of the bunker face. Ideally the face should be very smooth and straight. This minimizes oxygen exposure to the silage. Bunker silos with irregular and uneven faces have greater surface area exposed to oxygen and thus a greater chance at increased microbial activity.
- Silage color can indicate potential fermentation problems. Silages with excessive acetic acid will have a yellowish hue, while those with high butyrate will have a slimy, greenish color. Brown to black silage usually indicates heating from fermentation and moisture damage. These silages have the highest potential for molding and are unacceptable feeds. White coloration of silage is usually indicative of secondary mold growth.
- Silage odors can also be used to evaluate fermentation. Normal silage has minimal odor due to lactic acid. If acetic acid production is high, then silage may have a vinegar smell. High ethanol content from yeast fermentation may impart an alcohol odor to silage. Clostridial fermentation results in a rancid butter smell. Propionic acid fermentation results in a sharp, sweet smell and taste. Heat-damaged silages will have a caramelized or tobacco smell.