Groups of Irish farmers have been told that silage-feed losses can amount to 40% of the nutritive value contained within fresh grass.
This was the core message delivered by UK-based silage consultant, Jeremy Nash, who addressed a number of on-farm events over the past week.
Nash confirmed that good silage making centred on the retention of the nutritional value that is in fresh grass at time of cutting.
“Some losses are inevitable,” he explained.
“In a well-managed silage-making and feed-out system, losses of around 10% should be aimed for.
“However, in many farm situations, this figure is rising to 40% at the present time.”
Nash has adopted the principle of counting the forage wagons as they deliver fresh cut grass to the silo.
He explained:
“If final losses account for 20% of the initial grass nutritive value, this is comparable to one-in-five of the wagons dumping straight into a dunghill.
“But if the loss figure increases to 40% then this figure comparative figure rises to two in every five forage wagons.
“All of this adds up to real money being lost to any farming business.”
Silage loss- tips to reduce
Nash reviewed a number of practical steps that farmers can take to reduce silage losses.
He stressed the need for all aspects of a grass cutting and silage making operation to complement each other, adding:
“A bottleneck at any stage simply holds the entire process up.”
According to Nash, grass should be cut at a height that avoids any trash or decomposing debris getting into the pit.
“Farmers should walk fields prior to mowing in order to ascertain the right cutting height,” he said.
“Cutting that little bit higher can also ensure a much faster re-growth.”
“The old rule of thumb, pointing to the benefits of cutting grass in the afternoon and picking up 24 hours later, may still have some resonance if small acreages of grass are being ensiled.
“But where larger crops are concerned, the main requirement is to get the moisture out of the crops as soon as possible and achieve a consistent dry matter.
“Taking this approach ensures that the crops stops respiring as quickly as possible.”
Silage making
Nash pointed to the need for effective tedding in this regard. He further explained:
“I know that many farmers are keen to do some of the work involved in silage making, as a means of assisting the contractor.
“In these circumstances, I would strongly advise the procurement of a good tedder. It is the piece of equipment that will generate the highest level of payback.
“When it comes to rowing up the grass, the tines of the rake should be set at a height to ensure that they are not gathering up debris and trash, which will only serve to reduce silage quality from the get-go.”
Significantly, Nash suggested that forage harvesters are preferable – relative to forage wagons – when it comes to picking up and chopping grass in the field.
He commented:
“In my opinion, the harvester should guarantee a more consistent chop length. This is a key driver when it comes to making good, or high quality, silage in a clamp.”
When asked to confirm the optimal chop length for grass and other silages, Nash referenced the length of the forage that enters the rumen of a bovine animal after chewing.
He commented:
“Recent studies have shown that the average length of chewed forages dropping back into the rumen is in the range 7–11mm.
According to Nash, recent research has also confirmed the non digestible fibre (NDF) fraction of a forage as being a key driver from an animal nutritional perspective.
“Higher NDF levels can increase forage intakes, time in the rumen and milk butterfat levels but the NDF level is not determined by the chop lengths in most silage,” he said
“So it’s important that the silage-making process reflects these facts. It is easier to compact shorter cut forages. The shorter the chop length the faster the fermentation process can get underway.
Nash added:
“This is particularly so when forages have an inherently high dry matter. A combination of longer chop lengths and very high dry matters makes effective compaction almost impossible.
Where ensiling is concerned, Nash endorsed the principle of rapid filling and ensuring that air is removed from the pit as efficiently as possible. Compacting each six inch layer of grass is the target to be achieved in this context.
Nash commented:
“Bespoke compacters are now becoming very popular in England, particularly when large volumes of grass are to be ensiled.
“The evidence would indicate that these machines can increase bulk densities by up to 100kg per cubic metre of forage.
Silage top covers
Where top covers are concerned, Nash advised the use of materials that are light in colour.
He commented:
“Black is the worst of all colours that can be used to cover a silo. It absorbs most of the radiation falling on it. In turn, this heats up the forage below it.
“All biological processes are temperature dependent. And heating forages directly after their ensiling is completely negative in the context of what the silage making process is all about.”
Nash explained that freshly ensiled grass contains a mix of both aerobic and anaerobic microorganisms.
He added:
“It is critically important to reach the point at which silage becomes stable as quickly as possible.
“This will be achieved at around a pH value of 3.8 to 4.2, at which stage Lactobacillus plantarum will have become the predominant microorganism throughout the clamp.
But the silage specialist went on to make the fundamental assertion that the aerobic organisms within a clamp do not die on the back of the pH drop: rather, they go into a state of dormancy.
Most farmers get their silage analysed once a clamp has attained stability. It’s then a case of working out the best rations to feed over the coming winter months.
According to Nash, many farmers fall into the trap of thinking that the job is done.
“This is far from being the case,” he added.
“Up to this point, feed value losses of up to 10% may have been incurred.
“However, once the clamp is opened up additional losses can occur. And these can be significant.
“In some cases, we could be talking of losses amounting to 40% of the clamp’s original feed value.
“In other words, farmers will not be actually feeding silage of the same nutritive value as that assessed in the clamp.
“Given these circumstances, farmers should test their forages at point of cutting, once a point of stability has been reached within the clamp and then again at feed-out.”
When it comes to reducing these losses, Nash points to a number of steps that farmers can take.
Management of the clamp face is vitally important in order to reduce aerobic spoilage.
In this context Nash advises the use of a shear grab and the implementation of a policy on the part of the farmer to utilise the equivalent of one foot of silage depth – across the entire face of the silo – on a daily basis or the equivalent of 2m per week.
In the case of farmers feeding silage throughout the year, he advocates the silage depth figure to be increased by 50% during the summer months to 3m per week.
Alternatively, the option of putting a dividing wall in situ should be looked at.
“Aerobic stability is critically important, once the clamp is opened up as the aerobic microorganisms become active again,” said Nash.
At a more fundamental level, Nash stressed the benefits of securing stability within a silage clamp as quickly as possible: in other words securing a rapid pH drop.
“Inoculants work by pre-loading the forage with lactobacilli that can do this job as effectively as possible,” he commented.
“Bio-Sil contains a highly effective and patented strain of L. plantarum.
“The end result is the extremely efficient production of lactic acid, which brings about a very fast pH drop within the clamp.
“When this happens, the aerobic bacteria that can cause spoilage losses at feed out do not get a chance to establish a viable population
“So the farmer gets the aerobic stability required without the negatives, particularly where wholecrop and high dry matter grass silages are concerned.”
Nash continued:
“All of this has been proven courtesy of numerous trials carried out by Germany’s DLG, one of the world’s most respected testing and standard-setting organisations in the world.”
Significantly, Nash does not believe that enzyme-based inoculants are required to produce good silage under Irish conditions.
“This is because the sugar levels in Irish grasses are so high at time of ensiling. Enzymes come into their own when grass sugar levels are low.
“This is the case in places like eastern Europe. Enzymes work to break down grass cells and by so doing will increase available sugar levels. But these processes are not required if the available sugars are already abundant.”
He concluded:
“An inoculant should be regarded as an investment, when it comes to making good silage.
“Seeing its use as an insurance policy simply misses the point. An investment must deliver a payback. And in the case of Bio-Sil this figure will come-in around four or five-to-one, relative to the initial outlay.”