Bad bugs, bad bugs…What can you do?

Posted on June 18, 2019 in Forage Foundations
By Dr. Michelle Der Bedrosian, Vita Plus forage products and dairy technical specialist
This growing season so far has been marked by heavy amounts of rainfall.  First-crop alfalfa and small grain silages are coming off the field and, in many places, these forages are going into the silo quite wet. Silages that are too wet are predisposed for the growth of bad bacteria.  With many questions floating around, we want to answer two questions we are asked frequently.

Question one: I may have to put up wet silage.  What do I do?

Answer:  The presence of “bad bacteria” is inevitable in wet silages, but their growth is not.  Clostridia thrive in environments with high moisture levels (more than 70% moisture).  Their activity is detrimental, not only because of their potential effects on the gut (i.e. hemorrhagic bowel syndrome, Salmonellosis, etc.), but because they degrade silage quality.  Their activity results in high dry matter (DM) losses and poor-quality silage, and they can also degrade sugars into butyric acid and valuable proteins into biogenic amines and ammonia.  In short, Clostridia can excessively degrade silage nutrients.

What can you do?  Let the silage ferment for a minimum of three weeks, then feed it as quickly as possible before it goes butyric.  Clostridia take two to three months to grow, and, if you can feed the silage before the bacteria have a chance to grow, you can get more milk per acre from that same feed.

Prior to feeding, suspect silages should be tested for the growth of Clostridia and enterobacteria.  The end products of their fermentation should also be tested to see what is still present, such as volatile fatty acids (VFAs) and biogenic amines, and how much damage they have done.

Question two:  I got first crop off the field and I need somewhere to put manure.  Can I put it on the alfalfa?  How will this affect second crop?

Answer:  Yes, you can.  Put the manure on the field as soon as possible after harvesting first crop.  If alfalfa has time to develop leaves, manure application onto foliage can burn the leaves of the young plant, which is detrimental to its growth.  Also, the sooner you can get the manure applied to the field, the greater the chance for the manure to be incorporated into the soil by a rainfall event. Rain helps ensure “bad” microorganisms in the manure (such as enterobacteria) are washed off the plant.

Again, it may be a good idea to test the crop going into the silo to quantify whether any bad bacteria, such as Clostridia, enterobacteria, yeasts and molds, are present in the silage.  In addition, testing the end products of their fermentations for VFAs and biogenic amines may be a good management exercise.

At the end of the day, knowing exactly what we are feeding to our cows is invaluable.  Thus, testing for the presence of bad bacteria in our silage is useful.  It is also useful to know how much damage they may have done to the silage nutrient composition.  The best way to limit the growth of bad bacteria is with good management practices.  Using an inoculant, filling the silo quickly, excellent packing and using a true oxygen barrier plastic all can help reduce silage pH quickly.

Category: Feed quality and nutrition
Forage Foundations