Choosing an inoculant for earlage
With corn silage season approaching, decisions need to be made and practices need to be reviewed to make good silage. One of those choices is whether you should inoculate, and, if you do, which microbial forage inoculant you should select for your crop. Although these may sound like simple questions, many factors need to be considered prior to picking the best inoculant for your crop.
Why should earlage be inoculated?
Compared with whole-plant corn silage, earlage and other fractionated corn silages, like high moisture corn and snaplage, have less moisture, which is important to transport bacteria, and lower sugar levels the primary substrate for silage fermentation. Also, in the Upper Midwest, earlage is harvested in the fall when the epiphytic (natural) bacterial population is not as viable because of cool temperatures. Cooler temperatures at harvest and a lack of available sugars explain why earlage typically ferments slower, and to a lesser extent, than whole-plant corn silage.
Forage inoculants contain bacteria that take over the fermentation process and shift silage fermentation toward a desired pattern (mainly producing lactic acid and some antifungal acids) for optimum preservation. This may help in situations where the epiphytic bacterial population is unable to dominate the fermentation process, such as in earlage. Inoculating earlage would act as a safeguard for your crop investment. But, given the differences among forage types, it is advised to use a product designated for the crop you are ensiling. Look for an inoculant specific for earlage or high moisture corn as these would usually contain higher bacterial counts.
Which type of inoculant works best for earlage?
Bacteria commonly found in forage inoculants can be divided into two main groups, homofermentative and heterofermentative. The difference between the two are the end products produced during fermentation.
Forage inoculants containing homofermentative bacteria aim to maximize lactic acid production and maintain forage nutritive values close to what they were at ensiling. These bacteria convert sugars into lactic acid, which is a stronger acid than others produced during silage fermentation. Lactic acid accelerates the pH drop, prevents growth of undesired microorganisms and reduces protein degradation.
Heterofermentative bacteria, such as Lactobacillus buchneri, produce lactic and acetic acids and ethanol. Although these bacteria have a slower fermentation rate, they can convert lactic acid into acetic acid and 1,2-propanediol, as Table 1 shows. Acetic acid has antifungal properties and helps prevent silage from heating up quickly after being exposed to oxygen. This type of inoculant is suggested when ensiling crops are rich in starch or going into silos that will be fed during late spring and summer because those silages are prone to lower aerobic stability during those times.
If you think your silage could benefit from both types of bacteria, some inoculants combine these two types of bacteria.
Forage inoculants are a good technology to consider to safeguard your earlage investment. But remember, they cannot replace adequate silo management. If you use microbial inoculants, do your research and choose a product specific for the crop you are ensiling. Not all bacteria strains work the same, so it is important to consider research trial results, preferably by independent parties, and not mainly price when deciding which inoculant is the best option to help you reach your forage program goals.
Dr. Luis Ferraretto, University of Wisconsin-Madison assistant professor and extension specialist. This article appeared on Vita Plus' Forage Foundation website.