GETTING THE MOST FROM SILO
BAGS AND BUNKERS
NUTRITIONAL CONSIDERATIONS
Jim DeMatteo
In looking at he
nutritional value of forages, we have a lot of information to consider in the
equation between the field and the cow’s mouth.
In evaluating forage storage options, we need to
consider the income over expenses, rather than simply focusing on the first
cost. If we only focus on the first cost
of the storage option, we don’t consider what impact this decision has on the
bottom line. It’s like looking at the
cost to feed a cow, without considering income over feed cost.
Certainly some of the benefits gained by the better
preservation of a forage are cumulative, however the
benefits gained are for input into your individual value system. If we gained one pound of milk for every
additional cost that promised that kind of return, I wouldn’t be up here
talking about this now!
Assumptions
For our
purposes today, let’s make some assumptions about our starting point… We are talking about storage of a forage crop
whether it is corn silage or haylage, the ideas presented will run generally
true for both types of forage. Let’s
assume that we have an excellent crop of forage delivered to the site of
storage. We have selected a highly
digestible NDF hybrid. In the case of
corn silage, we have harvested with a kernel processor. The forage product is chopped at the ideal
length, the moisture is perfect, and we harvested at the ideal stage of
maturity. All of these elements are
extremely important. We can discuss storage
options all day long to no avail if the product was harvested at an advanced
stage of maturity. There are so many
components involved in delivering the optimum forage to the cow’s mouth, that we need to narrow our scope.
So, we’ve got an excellent quality product at the
site of storage. What needs to happen to
maintain that excellence product?
The Fermentation Process
1.
Microorganisms will ferment soluble carbohydrates.
2.
The byproducts of these microorganisms are volatile fatty acids… faster fermentation will yield higher levels
of lactic acid as compared with the other volatile fatty acids.
3.
The buildup of the byproducts of the microorganism’s
digestion (VFA’s) drop the pH to 3.8 – 5.0.
4.
Microbial growth is inhibited at these pH levels.
5.
Anaerobic conditions = stability.
We
eliminate the oxygen as soon as possible.
We fill the storage vessel as fast as possible, and we pack it extremely
tight. Then we seal it up to eliminate
the oxygen so that Mother Nature can do her work. Then, when we feed the product out, we manage
the face so that we continue to keep our exposure to oxygen at a minimum.
None of what we’ve talked about here is new
information. In fact, with all of the
technology that we have and with our mutual desire to consistently put up an
excellent forage product, why can’t we duplicate excellence time after
time. Because we continue to have the
variables of weather, distance to the site of storage, and equipment operation problems. The fact is, we farm in reality… and not dreamland.
Most would agree, that
given the variables that we all face; an AgBag has the best ability to fill the
fastest, pack the hardest, seal the tightest and feed out with the least amount
of face exposure. So, we CAN afford to
pay more for “ideal” storage conditions, but how do we consider the benefit
side of this cost equation?
Cost/Benefits of Storage
Options
Consider that 12” of brown mold that is the crust on
top of the bunk. It’s difficult to get a
great pack on that last foot or so in a bunk silo. I’ve been on farms all over the country where
that 12” is part of the shrink that you see.
In a 300’ * 40’ bunk silo, 12” in height equates to 270 tons of corn
silage {(1*300*40)*45 = 270 tons}. With
corn silage worth $ 17.00 per ton at the bunk, that
270 tons translates to $ 4,590.00.
A frequent “answer” to disposal of that “brown
crust” on the bunk silo is to feed it to the dry cows or heifers. Before we make that decision, I think it is
good to consider Britt’s work from
Or maybe that little bit of “brown crust” really
won’t hurt the lactating cows, they are generally
tolerant of molds anyway. Well consider
the analogy of someone taking a thimble full of mold and sprinkling it on the
top of your (otherwise excellent) meal.
Do you think that it might decrease your dry matter intake
slightly? Remember that one pound of increased
dry matter intake should yield two to three pound of milk. That again is difficult to figure as a
cumulative increase in income, but it does effect the bottom line… in extreme cases to
the tune of $ 0.24 per cow per day.
Or maybe you just throw away that “brown
crust”. Assume that you experience a
fifteen- percent shrink in your corn silage bunk silo instead of five- percent
shrink in AgBags. Assume that your corn
silage is worth $ 25.00 per ton upon feed-out.
That extra ten percent shrink effectively increases the price of that $
25.00 corn silage to $ 27.78 (assuming that the five percent AgBag shrink is
already figured into the $ 25.00 corn silage… calculated as $ 25.00/0.90).
Or consider that your AgBags that hold the same
amount of forage as a 12’ * 40’ * 300’ bunk silo will feed 444 cows 40# of corn
silage year round. Yet if the bunk silo
has that additional ten percent shrink, you can only feed 400 cows that same
amount of forage. If land base is a
barrier to your expansion project, you may want to consider the more expensive
storage with the payback of more cows fed per ton put up.
Or, if you are hauling forage product just a little
too far from the site of storage consider that you
only need 171 acres to fill the storage unit to feed 444 cows at five percent
shrink, where you will need 189 acres to feed that same number of cows at a
fifteen percent shrink. In order to make
the most use of your land base, it’s best to hold onto more of that excellent
quality forage that you started with.
It’s extremely difficult to determine the relative
value of different forages under field conditions. There has been an increase in the interest of
VFA analysis. Presumably, the higher the
lactic acid content, the better the preservation. This is true,
however I have found the lack of repeatability of VFA analysis to be a barrier
to its practical use under field conditions.
Certainly, you can smell if a forage product has that slightly sweet,
slightly sharp odor as compared to the rank of a forage laced with butyric acid… but this is a gross
analysis that simply measures the difference between good and bad. It would be nice to have more of a finite
picture of degrees of good and bad.
General wet lab forage analysis does tie some numbers to the quality
issue. Although it’s hard to compare,
generally speaking with a decrease in carbohydrates there is a tandem increase
in fiber.
Poor Fermentation Means Less
Energy for Production
When we have a fresh forage
we have a package of nutrients. The sum
of this package of nutrients will (of course) be 100 percent. When fermentation takes place the microbes
that produce VFA’s digest some of the soluble carbohydrates. This is a good thing. We can not demonstrate fermentation without
something for the “bugs” to live off of.
Once the carbohydrates are digested they are gone… If you take our fresh forage package at 100
%, and remove some of the carbohydrates in order to have fermentation take
place, the result is a new package size.
This package will still equal 100 %, however with less carbohydrates,
you will see a corresponding increase in fiber and other nutrients. As fiber increases, available energy
decreases.
There are several equations for the calculation of
energy. Here is a list of some of them…
NEl 1.014 - (0.011 * ADF) = Mcal/lb
NEl 1.044 - (0.0123 * ADF) = Mcal/lb
NEl (0.025 * TDN) - 0.12 = Mcal/lb
TDN 90.64 – (1.0599 * ADF)
TDN 93.414 – (0.9492 * ADF)
TDN 82.38 – (ADF * 0.7515)
If
1.0 # TDN = 3.0 # milk
Then
0.7515 % < TDN = 15.03 # < TDN/DM ton…
15.03
* 3.0 = 45.09 # less milk per dry matter ton of forage.
At
$ 12.00/cwt. Milk, that = $ 5.41 per DM ton less value in the forage for every
1.0 % increase in ADF.
All
of these figures may not be cumulative, however even if they are only partially
additive this begins to demonstrate that there is some additional value to be
considered in preserving more of the product that you work so hard to do an
excellent job producing.
If
you do NOT know what your shrink is currently running, don’t assume that you
are at a certain level. The reality is
that shrink of feeds and forages is one of the biggest expenses on the large
dairy.
If
you are going to go to the trouble of producing excellent forages… do it all the way through to where it
counts… the cows mouth.