Vacuum Silage in 2022
The Vacuum Silage self unloading trailer and flail forage harvester were moved to a farm in North Devon in the Spring of 2022. They were used to make Vacuum Silage on that farm and this page records what has been achieved as a new farmer experiments with the techniques and principles.
A field was mown using the JF Flail Harvester in the second week of June 2022 and the 7 acres was left in windrows. It was a very damp crop so it was decided to wilt for two days. However, a combination of damp weather and equipment preparation resulted in the forage being left in windrows for 4 days. It was sampled during that time to monitor what was happening to the forage quality. The results are below. SC means standing crop. Day 1, 2 and 3 were in windrows. Day 5 is the anaerobic sample after the Carbon Dioxide Response. The weather was not wet enough to cause leaching in windrows. It just stopped them from drying as quickly as expected.
On Day 5 the windrows were picked up by flail harvester and collected in the JF self unloading trailer and a clamp was created. After 55 % of the field was brought in, equipment failure stopped the collection so the clamp was sheeted down and sealed with the old Strip-Seal. Vacuum pumping began that day, but was not completed due to generator failure. The next day (Day 6) it was evacuated to 300 mbar (9 inches of Mercury) using the BL42 electric pump. The Carbon Dioxide response then inflated the sheets and that was evacuated on Day 8. Safety sheets and weights were then applied to hold the clamp.
Loss of Sugars in Windrows
This is not a scientific study, but there are two good stories in the data. The dry matter shows that the weather stopped the windrows drying out too much and the grass was at the right percentage going into the stack. The more dramatic story is in the "Sugars" data and shows just how fast they burn up and disappear if grass is left too long before being clamped, wrapped or bagged. About 40 % was lost from this forage in the three days in windrows.
Other measures, including protein were quite stable over the six days that were monitored.
The remaining 45 % of the field was made into hay after the silage clamp was pumped down. That resulted in the forage being in windrows for a further few days. Analysis of that hay are in the table below.
In August an incident resulted in damage to the clamp. Sheep punctured the sheet and let air in on the lower side of the clamp. This made it possible to monitor the degradation of the Vacuum Silage and there was an opportunity to sample the best silage from an undamaged part of the clamp. The sampling occurred six weeks after the damage happened when the clamp began to be fed out in September. The results are below.
For the Vacuum Silage, the headlines are that dry matter was on target at 34 %. Metablisable Energy was almost completely conserved in the Vacuum Silage. The sugars decline that was happening in the windrows was stopped the moment the forage went under the Vacuum.
The protein story has been quite stable all through the process from standing crop to Vacuum Silage. Very little proteolysis was happening in the windrows and that never got established in the sealed Vacuum Silage.
The pH of 4.3 and naturally produced Lactic Acid at 56 g/kg did the pickling job without any artificial additives. Just Vacuum. The Acetic Acid (vinegar) is left over from first phase fermentation at 13 g/kg. The silage smells like chutney, or sweet pickle, just as it should.
The main thing is that what went into the clamp was immediately conserved at the quality level it was when it went in. That is what all silage making should do. This is always the case with properly sealed Vacuum Silage Clamps. That is why the food industry uses this technique.
These results are not scientifically rigorous, but they are good enough to show trends and stories and give rough estimates of losses without being too detailed.
If we had managed to clamp the forage on Day 2 then the sugars would have been well above usual target levels (40 - 100 g/kg). Maybe next year that will happen. Watch this space. In the meantime the Day 5 level that was conserved at 87 g/kg for sugars is in the middle of the conventional target range. So that is a good result and better things are possible.
The Damaged Silage was damaged by sheep in a localised area and the change in silage quality over six weeks was measured by sampling directly from the affected area. The results are in the table below. The most interesting comparison is with the Vacuum Silage column. That gives a before and after story.
The damage caused punctures to the sheet, and air to get in to the clamp, and some direct contamination from the sheep’s feet occurred. That might explain the ash value change.
The smell of the silage was obviously more butyric and rank, and protein degradation gave the smell of rotting material. The silage was also heating up. This is consistent with Chlostridial infection. The smells indicate that the silage is becoming less palatable to livestock. The results show that Ammonium (NH3) had increased and that is one of the quickest and most noticeable indicators of protein breakdown.
The water content increased because of breakdown of dry matter, both sugars and proteins, producing water. The Damaged sample was producing effluent in the sample bag (21 % DM).
The pH was rising and Lactic Acid was being destroyed, with Butyric Acid and Acetic Acid taking over. That is consistent with Chlostridial activity. (Butyric Acid was not analysed, but you could smell it!)
Once again the most dramatic changes were in the sugars values. In six weeks roughly two thirds of the sugars in the Vacuum Silage had been destroyed. In one more month those values might be close to zero due to this secondary fermentation. This shows the potential damage occurring at feeding out if silage is not protected. The majority of this damage is due to exposure to air.
The results also show that, whilst effluent is not produced from wilted grass that is rapidly fermented, when silage is slowly fermented or allowed to break down or become contaminated then effluent is produced and losses can be highly significant. This sample was well on the way to becoming unusable.
The Hay sample showed a useful quality of forage that had been rescued from the field after Vacuum Silage had been made. Some loss of protein occurred over the additional days that forage was in windrows being made into hay.
Feed Trial Observations
The 2022 Vacuum Silage (above), the Hay (from the rest of the same field) and the Damaged Silage were all put in front of some housed sheep to observe feed preferences in October. Some sheep were new to silage and took hay first. Once they had tried Vacuum Silage, all sheep took that in preference to Hay. They only ate Damaged Silage if it was the only thing in front of them.
Preference order: Vacuum Silage, Hay, then Damaged Silage.
The Vacuum Silage was therefore more readily consumed as well as having the best nutritional analysis. This means that there may be an advantage in making Vacuum Silage rather than hay for forage conservation.
If the silage is poor quality, however, then it might be better to make hay.
This also confirms that intake is reduced if silage is allowed to spoil.