Editor's note: The following article appeared in the University of Florida's "Dairy Update" newsletter, summer 2011 edition.
The Southeast Dairy Check-off funded two experiments aimed at comparing different strategies of reducing silage spoilage.
Experiment 1: Additive type effects
Chemicals and bacterial inoculants are frequently applied to forages at the time of ensiling to improve the quality and shelf life of the resulting silage. The objective of this trial was to evaluate the effect of several different chemical and bacterial additives on silage fermentation and aerobic stability.
Corn forage was harvested at 31 percent of dry matter and chopped.
The treatments applied were:
1) Water (Control treatment).
2) Buchneri 500 Combo inoculant (BUC) from Lallemand Animal Nutrition (supplied 100,000 colony forming units (cfu) per gram of Pediococcus pentosaceous and 400,000 cfu per gram of Lactobacillus buchneri bacteria).
3) Sodium benzoate (BEN) applied at 1 percent of fresh forage weight.
4) Silage Savor acid mixture, (SAV) from Kemin AgriFoods North America, Inc. applied at 1 percent of fresh forage weight.
5) Acetobacter pasteurianus experimental inoculant bacteria (PAS) applied at 1000,000 cfu per gram.
6) Gluconobacter suboxydans experimental inoculant bacteria (SUB) applied at 1000,000 cfu per gram.
7) MTB 100 inoculant (ECO) from Ecosyl Inc, Byron, Ill., applied at 1 gram per ton.
8) Silo-King Water Soluble inoculant (SK) from Agri-king, Fulton, Ill., containing Lactobacillus plantarum, Enterococcus faecium and applied at 6 grams per ton.
9) Biomax V inoculant (BIO) from Chr. Hansen Animal health and Nutrition, Milwaukee, Wis., containing Lactobacillus plantarum and applied at 1 gram per ton.
After additive application, each treatment was packed into four, 5-gallon laboratory silos, which were sealed for 120 days. Silage samples were analyzed for fermentation products, nutritive value, and bunk life. All silages were well fermented as shown by low pH values (3.7 to 3.9).
Treatments did not affect dry matter digestibility.
Treatment SAV produced higher ammonia-nitrogen and butyrate concentrations than other treatments suggesting it increased protein degradation.
Treatment BEN gave the lowest pH, ethanol, and ammonia nitrogen concentrations indicating that it improved fermentation efficiency and reduced protein degradation.
Treatment BUC gave higher acetate concentration than the Control and the longest bunk life (44 hours). This may be because acetate is an antifungal compound that reduces the growth of spoilage organisms.
Compared to the Control silage, BUC silage had 64 percent longer bunk life and BEN silage had 37 percent longer bunk life but other treatments did not improve bunk life.
In conclusion, chemical and bacterial inoculants can improve the fermentation and aerobic stability of corn silage but the efficacy varies with the additive.
In this study, the Lactobacillus buchneri inoculant, Buchneri 500 and sodium benzoate were the most effective additives for improving the bunk life of the silage.
Experiment 2: Cover type effects
This experiment aimed to examine effects of different silo sealing strategies on the quality, shrinkage and bunk life of corn silage. In particular, we compared using Silostop oxygen barrier film instead of conventional plastic to cover silage in bunkers.
Bruno Rimini company claims their Silo-stop film is up to 60 times more effective at reducing oxygen flow through the film into silage than conventional plastic, and therefore it can increase bunk life and reduce silage spoilage.
In a previous study at the University of Delaware, using Silostop improved fiber digestibility of corn silage at the ‘shoulders" of bunker silos. The shoulders represent the area that is 4 inches away from the sidewall and in the top 6 inches of the bunker.
In a previous study at the Dairy Forage Research Center in Madison, Wis., shrinkage (dry matter losses) was greater in the top 6 inches of corn silage covered with conventional 8-mil plastic compared to that covered with Silostop film. These studies suggested that the main benefits of Silostop were at the top layer or near the side walls.
In this experiment, we compared the following treatments:
1) Conventional 6 mil plastic cover on the top of the bunker (CONTROL).
2) Conventional 6 mil plastic on the top and sides of the bunker (SIDEWALL).
3) Conventional 6 mil plastic on the top and sides of the bunker with an added Silo-stop oxygen barrier film on the top of the bunker (SILOSTOP).
Three 40-ton silos (14 x 20 x 9 cubic foot) were made for each treatment in the fall of 2010 and these were opened in May 2011.
In each silo, twelve 2-pound bags of corn forage in mesh bags were buried during packing at depths of 1 foot and 4 feet from the surface and at widths of 2 foot or 5 feet from the sidewalls.
After the silos were opened, the bags were removed and analyzed for shrinkage, bunk life and nutritional value. We also measured the thickness of the darker slimy layer of spoiled silage on the top of the silage in each bunker.
A thick layer of spoiled silage was present on the top of the silage in each of the Control and Sidewall bunkers. However, this layer was completely absent in one of the 3 Silo-stop bunkers.
The thickness of the top spoilage layer was about 50 percent less in the Silostop bunkers than in Control or Sidewall bunkers.
However, cover type had no effect on measures of fermentation quality, nutritive value, shrinkage or bunk life of the silage stored in the mesh bags at the different locations.
Distance from the sidewall did not affect silage quality, shrinkage or bunk life, perhaps because these were small, narrow silos. Although covering the sidewall with plastic may be important for large silos, our results suggest that it may not be necessary for well-packed silage in narrow bunkers.
Silage in the top 1 foot of bunkers had 90 percent more shrinkage (dry matter loss), lower pH, less lactic acid, and more ammonia-nitrogen than silage that was 4 feet below the surface. This showed that the silage in the top layer was poorly fermented and had more protein degradation, but silage in the lower layer was well fermented with little protein degradation. The poor fermentation and greater shrinkage of the silage in the top layer show that it is important to pack silage in the top layer to a greater density than silage in lower layers and to cover it immediately.
This may be because silage in the top layer is not weighed down by silage above it.
This study also suggests that the Silostop film reduced the amount of silage spoilage in the top layer. This spoiled top layer could contain molds and mycotoxins. A Kansas state University study showed that mixing the spoiled top layer silage with good silage reduced fiber digestibility and feed intake in beef cattle.
The cost effectiveness of using Silostop film will depend on the size of the bunker and the cost of normal plastic and Silostop film.
In addition to the financial aspects, producers who plan to use Silostop should note that the procedure avoids the need for tires or tire sidewalls to cover bunkers because sandbags are used to secure the film. However, the sandbags are heavy and could be more difficult to stack than tire sidewalls.
The Silostop procedure used in this research is called the 2-step procedure. It involves using just as much plastic as for a conventional silo, but a newer Silostop film from the company that requires less plastic has just been developed (1-step procedure).
We hope to test the new and old films on large bunkers in the future.
Contact Adegbola Adesogan at: firstname.lastname@example.org for more information.