We often speak of forage yield from the standpoint of the crop being grown and harvested in the field.  It's here that we have the chance to increase, or at least maintain, the yield potential of the crop.  In the case of forage crops, however, the same yield gained from good decision-making and management can easily be lost once it is put into storage.  Post harvest yield loss is expensive because the cost of harvesting is added to the value. 

        Silage inoculants help to maintain harvested silage yield and quality.  What they do and how they do it is often misunderstood.  Not all silage inoculants are created equal, nor do they provide same benefits.  Table 1 shows the dry matter losses that can occur with good and poor silage management.  Inoculants have the potential to reduce losses incurred from fermentation and storage (aerobic degradation).  They typically do not help with respiration or seepage losses. 

        Make no mistake........silage fermentation is a war between the good bacteria and the bad bacteria (along with molds, and yeasts).  The goal of any forage producer is to make sure the good guys win.  One way to do this is to control the front end of fermentation with by overpowering the system with lactic acid producing bacteria.  These bacteria increase the amount of lactic acid produced and speeds fermentation, which results in a faster drop in pH.  This reduces protein degradation and allows for higher dry matter (yield) and energy recovery.  Lactic acid producing bacteria are a preservation tool for yield and quality, they are NOT a yield and quality enhancing tool (if garbage goes into the silo, garbage will also come out). 

        One of the misconceptions about silage inoculants is that they improve aerobic stability.  This is only partially true.  Silage inoculants with bacteria that produce only lactic acid (called homofermenters) may actually decrease aerobic stability in some situations.  Hence, a good "front end" fermentation does not necessarily lead to stability during storage and feed-out.  To accomplish this, a Lactobacillus buchneri inoculant must be used.  L. buchneri produces lactic acid but also produces moderate amounts of acetic acid (called a heterofermenter).  Acetic acid is similar to propionic acid in that it retards yeast growth.  This reduces heating in the presence of oxygen.  L. buchneri's effectiveness is well documented in research trials with corn silage, alfalfa silage, high moisture corn, and cereal silage. 

        In 2007, corn silage samples were collected from 15 farms were no inoculants was used and 16 farmes using a L. buchneri product.  Partial results from the study are presented in Table 2.  Note the effectiveness of L. buchneri in reducing yeast counts and increasing aerobic stability. 

        When considering L. buchneri, realize that there is some tradeoff.  Although aerobic stability is improved, dry matter recovery will typically not be as high as it would be with a standard lactic acid bacteria inoculants.  According to Limin Kung (University of Delaware), situations where L. Buchneri offers the greatest benefit include:

·      High moisture corn

·      Corn silage

·      Drier (>40% DM) haylages and grasses

·      Silage fed during warm weather

·      Silage fed out slowly

·      Silage that will be moved between silos

·      Silage fed from intermediate feeding piles 

        A third type of bacterial silage inoculant on the market is comprised of both lactic acid homofermenters and L. buchneri heterofermenters.  As you might expect, these products offer intermediate benefits of both types of bacteria. 

Applying inoculants…

        When filling a bunker or pile silo, the preferred point of application is at the chopper.  This insures a uniform application throughout the forage mass.  Accomplishing the same uniformity if applied at the silo is difficult to impossible.  When filling an upright silo or bag, application of the inoculant can be done either at the chopper or the point of entry into the solo or bag.  Remember, inoculants are live bacteria and it’s your job to keep them viable.  Store products in a cool environment and don’t allow water in application tanks to exceed 100 degrees.  In summary, silage inoculants are a great tool preserve high value post-harvest yield, but it’s important that users realize and understand their potential benefits and limitations.