Producers can evaluate their silage in several ways before it hits the feedbunk. Best practices recommend taking representative samples for comprehensive near-infrared (NIR) analysis on a regular basis. Wet chemistry analysis should be considered and compared to NIR analysis in atypical years (floods, drought, etc.).
Dry matter (DM) content is the first indicator of how close to maturity the crop was at harvest and ensiling. Anything less than 32% DM indicates a less mature crop and potential for silage effluent seepage in the bunker or pile. Excess effluent seepage creates a pollution risk if not managed correctly and also represents a loss of the most digestible nutrients in the crop.
Expect the starch content of the crop to be in line with the crop’s maturity. High-moisture, immature crops will likely have much lower starch content — less than 30% on a DM basis. Extreme cases may be less than 20% on DM basis.
Be aware that this immature corn is likely to contain more sugars that ferment readily in the rumen, as well as create silage that has higher total acid content. Risk of aerobic instability or wild-spoilage yeast activity increases with immature corn silages possessing elevated sugar levels.
In years where the crop experiences flood, drought or other atypical conditions, additional measurements are recommended, such as:
- Seven-hour rumen digestibility
- Digestibility rate per hour
- Ash, organic acids and ammonia-N
- Yeast and mold counts, if needed
Pay close attention to the neutral detergent fiber (NDF) content of the crop, listed in the analytical report as “aNDF” content. Expect higher aNDF values on a DM basis in low-starch crops. Know the aNDF digestibility and the associated rate of aNDF digestion, along with the indigestible NDF fraction or ballast shown as “uNDF240” content. These measurements can be important when making stressed forages work in the ration.
Finally, within the analytical report, it’s worth looking at the total ash content and fermentation profile. The ash content of corn silage is typically 3% to 5% on a DM-basis. Anything higher than this represents dust or soil contamination, with the risk of unwanted inoculation by harmful microbes within the dust/soil contaminant. The extent and type of fermentation achieved depends on whether or not an effective inoculant was used and the efficacy of the whole ensilage process.