“There are lots of pieces to the puzzle when it comes to preserving silage,” commented CNY Regional Dairy Specialist, Dave Balbian, co-coordinator of several Central NY PRO-DAIRY Feeder School programs, which took place statewide.
Balbian and Cornell’s Dr. Jerry Bertoldo led a two-part program in Chenango County, which included an ‘on farm training’ at Postma Brothers Dairy, West Edmeston, NY.
Balbian explained that adequate packing, a basic requirement that cannot be overcome with other practices, is often problematic.
“The use of these large self-propelled choppers sometimes means that forage delivery rates to the bunker silo are too high for the amount of tractor packing weight being used at filling,” said Balbian. “To determine minimum packing weight, take the fill rate in tons per hour and multiply it by 800. That will give you the minimum weight, in pounds, of packing tractors needed to be continually packing during filling. The answer often means there needs to be more than one tractor and/or heavier tractors packing.”
Bertoldo explained further. “The pounds per square foot is the measure of how well the silage was packed with tractors when the bunk is being filled. We aim for 15 pounds or greater of dry matter per cubic foot. It is a more reliable measure than as is moisture pounds per cubic foot. The drier the material being packed the harder it is to get decent densities. Low density correlates to less than desirable amount of air being forced out.”
Balbian advised using a long compost thermometer deep into the feed, to check temperatures of silage, helping to determine if air was adequately excluded from the silage. “The reading should be no more than 10 to 15 degrees above the ambient temperature when the silage was harvested.”
For instance, if the temperature is 75 degrees when delivering and packing the silage, the temperature of inner silage should be no more than 85–90 degrees when in the bunk and used for feeding.
Balbian distributed charts to attendees to help explain the required weight desired for adequate packing as compared to the amount of time each load is delivered.
Bertoldo said AgBags may have an advantage over bunks for silage.
“If set up correctly they exclude air well and create even densities,” Bertoldo explained. “As long as the plastic does not split — or birds and rodents chew through it allowing air to enter, the fermentation is usually good. You can get away with a wider dry matter range and avoid the negatives that come with that in bunks.”
Bertoldo said one disadvantage when using an AG bag is the lack of being able to blend varying forage dry matter and growth characteristics from different fields or even the same field, when packing. “With bags, and uprights, the variance of feed quality can be on a daily basis,” commented Bertoldo, “whereas bunks, with the layering from many field sources, evens the differences out.”
“Quality is at both ends of the process,” Dr. Bertoldo clarified. “When going in, and when being fed out. Coming out of the field we need to consider dry matter, chop length, kernel processing score, packing density and, in some years, pre-existing molds.”
On the feed-out side, Bertoldo explained that other factors need to be seriously considered.
“We have fermentation product profile.”
This includes VFA totals, lactic to acetic acid ratio, butyric acid, which is harmful to the cow; and how much energy — starch in particular — has survived ensiling.
“Does the silage heat up after air is mixed in?” This is a sign that yeasts and molds are growing.
“Is there obvious nasty stuff on the top or along the walls?”
Covering the bunk is especially important to prevent loss — and therefore dollars — and some time was given to describing how several farms have designed exceptional covering procedures to preserve silage in their bunks.
“Bunk packing and particularly the question of density — pounds per cubic foot of silage — is important in order to promote good fermentation,” Bertoldo explained. “The fermentation of sugars in the chopped forage by lactic acid producing bacteria, naturally present or added via inoculants, reduces the pH of the silage mass and in effect ‘pickles’ the corn or hay crop silage. The initial goal is to force out as much air/oxygen as possible when filling the bunk, upright silo, or AgBag.”
Bertoldo emphasized that desirable (good), acid producing bacteria do not like oxygen. However, undesirable (bad) bacteria — like yeasts and molds — do like oxygen and will reproduce and grow in its presence.
“If the bad ones get a head start, they reduce the quality of the silage and can produce compounds that are not healthy for the cow’s gut. Bad bugs do not grow well — or at all — in lower pH environments.”
In most situations, final pH in silage should be below 4.5 to prevent loss of dry matter and value while being stored and to prevent overheating at feed out.
“Finer chopped forage will be digested more quickly than coarse stuff,” Bertoldo remarked. “But,” he emphasized, “if we don’t have a critical amount of coarser forage to make that rumen mat then that advantage will be lost due to less retention and therefore digestion time in the rumen.”
Bertoldo explained the importance of developing the rumen mat in a presentation prior to the on-farm training session.
“In reality, we really have to consider what is going on inside that rumen! If we don’t have that effective fiber, we kind of goof up the system. The rumen mat and effective fiber level is key to how much saliva they produce.”
Bertoldo said kernel processing or crushing is a separate issue.
“The interior of the kernel must be exposed to have the starch fermented to VFA’s (volatile fatty acids) in the rumen. It is both an access to the starch by bugs (rumen bacteria needed for ideal rumen health) as well as a softening of the starch by the rumen fluid. So, the drier the kernel the more crushing it needs. Cracked dry corn has to be pretty fine to digest efficiently whereas kernels in a normal 35 percent dry matter silage can be 1/4 or 1/2 size and do okay.”
Bertoldo emphasized the importance of feeding the rumen bacteria to keep the gut happy in dairy cows.
“TMR (total mixed ration) gives us a real advantage to keeping the bugs happy. The bugs like a balanced, boring diet that changes very little on a daily basis,” Bertoldo explained. “It’s a really complex system.”