An initiative entitled ‘Cut to Clamp’ has been launched by Volac to help grassland farmers to make the most of silage and improve their efficiency and profitability. We feature extracts from the Cut to Clamp website.
As grass approaches heading, yield increases. However, leave it too late and protein, digestibility and metabolisable energy all decline. After heading, the digestibility of grass falls by about 0.5% a day. Delaying cutting may produce a heavier crop, but its nutritional value will be lower.
For good quality silage at an acceptable yield, cut just before heading. Similarly, although it might be tempting to cut low as this increases yield, the stem base is the part of the plant with the lowest digestibility. So again, overall quality will be improved by cutting higher. On top of that, dead material in the sward base contains higher levels of undesirable micro-organisms which hinder fermentation and increase aerobic spoilage.
Wilting increases the per cent dry matter and reduces losses from effluent. It also means the silage will stabilise at a higher pH so less acid, hence sugars, will be required. The problem is, as soon as grass is cut, sugars start declining because they are being used up by the plant, since it is still living, and by undesirable bacteria. A higher DM will also inhibit undesirable clostridia bacteria. The aim should be to wilt as rapidly as possible to an ideal target DM of 28-32%, but no longer.
Using the optimum chop length is crucial when harvesting grass because it has a big impact on how good a consolidation you can ultimately achieve in the clamp. Silage is produced when beneficial bacteria ferment some of the sugars in grass to lactic acid. This ‘pickles’ the grass, preventing the growth of spoilage micro-organisms and so preserving nutrients. However, fermentation only starts once there is no air left in the clamp. So, the quicker you can achieve this, the better.
Too long a chop makes it more difficult to squeeze all the air out of the spaces between the grass, particularly at higher dry matters, but too short a chop can also cause problems. As well as keeping knives sharp, ensure they are correctly adjusted according to the crop’s per cent dry matter. As a guide, if grass is >30% DM, chop to 1.5-2.5cm length to improve consolidation (though if grass silage is being fed as part of a high maize diet, chop length should be increased to ensure sufficient effective fibre in the complete diet). If grass is at 20-30% DM, use a chop length of 2.5-5cm. If grass is <20% DM, you may need to increase up to 10cm to reduce effluent and prevent clamp slippage.
Trials across a range of forages have shown that treating with a proven additive, such as the MTD/1 strain of Lactobacillus plantarum found in Ecosyl, can do much more than just act as a preservative. Across 15 grass silage trials, dry matter recovery with MTD/1 was boosted from 91.8% to 95.5% of the original material ensiled. Correct silage density Achieving the correct silage clamp density and effective sealing are critical factors in producing a successful clamp. Good consolidation to squeeze out as much air as possible is key.
Achieving the correct silage clamp density and effective sealing are critical factors in producing a successful clamp. Good consolidation to squeeze out as much air as possible is key.
For grass at 30% DM, aim for a target silage density of 250kg of DM/cu.m (750kg fresh weight/cu.m). If you trap too much air in the clamp when you ensile the grass, you reduce fermentation quality and increase aerobic instability problems at feed-out. Often, silage is not consolidated enough simply because trailers are arriving at the clamp too quickly and grass is not spread properly. You can only really efficiently consolidate the top 15cm. Layers should be even and no greater than this depth, before being compacted and the process repeated with the next layer. For effective consolidation, consider using a compacter which equals the full width of the tractor, so you are not just consolidating beneath the tractor wheels. Pay particular attention to the edges which are more difficult to consolidate. Also, avoid over-filling the clamp. Once clamps are filled above the walls, density drops.
Once consolidated, sealing the clamp will stop air/oxygen ingress, which is essential for fermentation and aerobic stability. Use side sheets and leave a good overlap with the top sheet of 1.5 metres. Once the clamp is filled, the side sheet should be folded in, an oxygen barrier film placed on top and then a top sheet. Always put as much weight on top of the clamp as possible. That top weight maintains better density in the weakest part of the clamp, which is the top. Remember to pay attention to the ramp. If carbon dioxide is allowed to seep out of the bottom of the clamp (because it is heavier than air), it creates a vacuum, which sucks oxygen in. So, as well as sheeting the rest of the clamp correctly, ensure there is at least half-a-metre of extra silage sheet at the front of the clamp, and weight it down well all around the edge.
The cleaner the clamp area, the better. Mouldy silage or dirt in front of the clamp will contaminate the silage with undesirable bugs, reducing quality and reducing intake. Do everything you can to avoid producing spoiled silage. If you have got it, discard it. Never mix it in with good silage. As well as being of poorer quality, it also adversely affects the rumen fermentation. To take silage out of the clamp, use a shear grab. This maintains a smooth clamp face with a lower surface area and a better face density than simply ripping it out. This reduces the amount of air which gets in so there is less risk of aerobic spoilage (heating) causing losses of nutrients and potentially production of mycotoxins.
For the same reason, move across the face quickly to reduce the time silage is exposed to air. It is important to avoid pulling or cutting the top sheet back too far once the clamp is opened and to keep the front edge weighted down. Avoid pulling the sheet back down over the clamp face. This is because it creates a microclimate, which encourages yeasts and moulds, increasing the risk of spoilage and heating.
Finally, get a silage analysis done and pay attention to it. It will tell you how good a job you made of silage-making last season and help you to pinpoint ways in which this year’s silage production can be improved. rFull details including videos are available at www.cuttoclamp.com
A survey of 100 dairy farmers conducted ahead of last season showed many felt they were not in control when it came to producing grass silage. In the survey nearly four out of five (78%) farmers questioned said they thought they could make better silage. Only one in five (19%) said they felt completely in control of how well their grass silage turned out once they had sealed the clamp. The survey was conducted by the manufacturers of silage additive Ecosyl.
Product manager Jackie Bradley says: “It was only when we dug deeper into silage-making practices we uncovered fermentation as providing some key opportunities for improvement. For example, only half of respondents realised that crop dry matter at harvest has a big impact on grass silage fermentation, while some aspects of the forage ‘pickling’ process which takes place as a result of fermentation also seemed poorly understood.
“During fermentation, beneficial bacteria convert some of the crop’s sugars into acids, which pickle the forage,” says Mrs Bradley.
“Yet only 20% of respondents recognised fermentation as a process whereby forage is pickled in acid. Also, 28% of respondents thought a good silage fermentation was largely dependent on the bacteria naturally present on grass.
“Relying solely on the bacteria on grass effectively reduces your control of preservation – because you don’t know if you have enough of the best type of bacteria for a fast and efficient fermentation.”
Looking at other aspects of clamp management from the survey, Mrs Bradley says although 90% of respondents did roll continuously when consolidating, only 38% said they normally filled the clamp in layers no more than 15cm thick, which is the maximum depth which can be consolidated effectively. She says: “Only 17% said they achieved a grass dry matter density of 250kg/cu.m when consolidating, which is the optimum for grass at 30% dry matter. If you want to maximise self-sufficiency in home-produced forage, good grass silage is a valuable asset. However, producing it is a joined-up process.”