Whether Mother Nature suddenly turns against you or the crop isn’t harvested quite at the moisture you expected, some years the silage fermentation process just doesn’t work out the way it’s supposed to or the way you’d like it to.
During anaerobic silage fermentation, microorganisms feed on sugars and other soluble carbohydrates in the forage material and produce organic acids, such as lactate and acetate. This lowers the pH and creates an environment where the resulting silage is preserved, writes forage expert Joel Bagg.
An efficient fermentation is desirable for two reasons:
- To preserve nutrients to optimize livestock intake and performance
- To minimize forage dry matter lost in the fermentation process and spoilage at feed-out
Fermentation losses can be 12 percent to 15 percent with a good fermentation, and much higher with a poor one. Spoilage losses can be significant.
We know what we have to do to make good silage – cut at the right maturity and moisture, chop at the right length, use inoculants strategically, keep it anaerobic (without oxygen) by filling the silo quickly, adequate packing, covering and sealing it well and right away, face management, etc. However, sometimes things don’t go well and we end up with high fermentation losses, poor nutrient quality and palatability, and silage that wants to spoil easily. It can be useful to determine what went wrong and know how to avoid that the next time.
Common Silage Problems
When we encounter problem silage, it is usually the result of incorrect moisture or the presence of oxygen. Odors can be good indicators. Here are a few problems that we might smell and what might have caused them.
Rancid, Fishy Odor
This is butyric acid resulting from clostridia contamination from soil. Clostridia silage can result from cutting or raking too close to the ground, soil from packing tractor tires, “splash” from rain or manure applied too late after the previous cutting. Butyric acid also commonly results from silage that is too wet (> 70 percent moisture). As well as its foul odor, this silage sometimes has a slimy, sticky texture. Haylage can clump into characteristic “butyric balls.” Fermentation losses of nonstructural carbohydrates are high, so ADF levels are high. Protein is degraded. Palatability, intake and digestible energy are low, and livestock performance is poor.
Moldy With A Musty Odor
Moldy silage results in high dry matter losses as well as poor palatability and livestock performance. This spoilage is the result of aerobic (oxygen) conditions from poor packing, slow filling, low moistures, poor sealing, slow feed-out or poor face management. If the silage is still hot, microbial activity and spoilage is still underway.
Acetic acid is more commonly known as vinegar. Lactic acid is the most desirable product of fermentation because it is produced most efficiently, with the least dry matter losses. Too much acetic acid relative to lactic acid means the fermentation was less than optimally efficient, and possibly could have benefited from a commercial lactic acid bacteria (LAB) inoculant.
This smell is likely high concentrations of ethanol produced by spoilage yeasts, mixed with acetic acid. Fermentation losses were likely high, and this silage will be prone to heating and spoiling in the bunk. Desirable lactic acid has little smell.
This indicates excessive protein breakdown to ammonia and amines, which could be due to a clostridia fermentation or high pH.
This heat-damaged haylage is dark in color with a tobacco odor. In severe cases it can smell burnt, indicating excessive heating. Heat-damaged silage is the result of forage that is too dry. Protein becomes bound and is less digestible. ADF-N (unavailable nitrogen) can be measured in a laboratory.
A technology available in silage problem-solving is fermentation analysis. It enables us to objectively quantify what we subjectively see and smell. This can be especially useful when poor livestock performance cannot be explained by nutrient analysis.
Table 1 – Typical Levels of Silage Fermentation End-Products (dry matter basis)
Whatever the results of your fermentation analysis, the reality is that you’re likely stuck with the silage you have for the year. But, using what you see and smell, combined with a fermentation analysis as a diagnostic tool, can help in identifying what can be improved in your silage making in the years ahead.
For more information on silage making, visit the OMAFRA Forage Website.
Original article written by Joel Bagg, retired forage specialist.