Wholecrop cereal silages represent the most diverse forages produced on UK livestock farms. They are diverse both in nutritive value and fermentation quality and very often this is due to the decisions made between sowing and harvest. Often these decisions are made late in the season as a result of external factors, such as weather to fill the forage gap caused by the drought. But was this the best option? As with all forages to be ensiled it is important that the producer of the silage is aware of all factors, often conflicting, before making decisions on how and when to harvest. The target must be how that silage will fit into the jigsaw puzzle of available feeds and the class of stock being fed on the farm to balance yield and quality with the requirements of the stock to produce milk or meat as efficiently and cost effectively as possible. Within this article I hope to highlight points to be thinking of when making your decision.

Pure cereal silages – the traditional approach to wholecrop
Many farmers consider wholecrop to be a high energy crop, but in fact this is not the case. In a report examining all the silages submitted for analysis through the Farming Connect Knowledge Exchange Programme in Wales from 2014-2017, the average wholecrop analysis had a metabolisable energy (ME) of 9.6MJ/kg DM and crude protein of 12.2g/kg DM with the top 20% only achieving an ME of 10.3MJ/kg DM and a crude protein of 15.4g/kg DM. This compares to the same dataset for grass silages submitted, where the average was 10.3MJ/kg DM and crude protein was 13.1g/kg DM, with the top 20% being 11.6MJ/kg DM of ME and crude protein of 16.6g/kg DM. Thus, the question should always be, what do I want to achieve with the wholecrop silage and is this the best option for harvesting the cereal?

The answer to that question is not a straightforward one, as there are a number of other factors that need to be considered.

First and foremost, it is important to remember that around 70-75% of the weight of the wholecrop forage is straw, with 25-30% being grain. Harvesting by combining either at the crimping or dry stage allows flexibility in feeding the straw and grain separately at the required levels to match the ration to the class of stock being fed in terms of nutritional and structural requirements. Even in a year where forage is short, harvesting at the grain stage will enable precise quantities of straw to be fed, rather than relying on the mix that was harvested as the wholecrop.

In a year with compromised forage yields, the quantities of straw fed can be increased to offset the yield lost by other forages, but this is still a more precise way of managing the crop than the wholecrop approach. The problem with the straw part of the wholecrop is that it has poor digestibility – around 50% maximum – and it has a slow passage rate. Thus, in productive livestock it will reduce the intake of the whole ration, and consequently reduce production, be that meat or milk. However, it is advantageous in maintaining a good supply of effective fibre and maintaining a healthy rumen. Thus, it is a balancing act. For the non-productive animal such as dry cows, be they dairy or sucklers, then wholecrop is a potential option.

If this traditional wholecrop approach is the best option for you, it should be harvested at around 35-37% DM and the grain should be at the soft cheese stage of growth. Many producers harvest at dry matters above this to maximise starch yield. However, if a corn cracker is not working effectively during the harvesting process, whilst the forage may contain more starch, a bovine animal consuming the wholecrop will not be able to digest the starch efficiently and much of the grain will pass straight through the animal undigested. This will result in a much larger loss of starch than harvesting at the earlier stage of growth.

If the wholecrop is to be baled, then a maximum dry matter of 35% should be the target as baled silage will not have a grain processor and the softer grains are less likely to pass through the gut undigested. Once harvested, the wholecrop should be chopped to a maximum chop length of 3cm to ensure good compaction. Remember, wholecrop is a dry crop with a lot of straw. Good compaction is absolutely key to maintaining good aerobic stability at feed-out. Chopping finely has two effects in wholecrop silages: it aids better compaction of a dry crop and it shortens the length of the straw for gaseous movement (CO2 out and O2 in) into the clamp face at feed-out.

Remember straws are used by children to have fun at parties making a right royal mess. Long chopped straw in your clamp enables yeasts and moulds to have fun at feed-out of your clamp, again making a right royal mess.

Green-crop wholecrop – is this a better option?
If we look away from these shores and examine what is happening in drought ridden countries of central and southern Europe, Israel, and certain parts of the USA, we find that cereals harvested as silages are now being taken earlier and used as a replacement for grass silage that cannot be grown due to heat and drought. These silages can have 18% crude protein, D-value of 75% and an ME of 12MJ/kg DM. To do this these crops are harvested before any seed stem has emerged from the sheath, so they have no starch but their purpose is to provide highly digestible cell walls. If they are harvested at this stage of maturity, they will regrow as a grass and can produce a second harvest. Harvest management is just like that of any standard grass for ensiling.

This approach would suit many UK
growers who are in drought-prone areas who grow maize. High maize inclusion in diets generally supply plenty of starch, but fibre digestibility and protein are low so the two forages complement each other well.

Drilling in the autumn and harvesting prior to drilling maize also eliminates the issues associated with over-wintering bare stubbles.

If you already suspect you may be short of forage early enough in the year, taking two cuts of a cereal destined for combining may be a far better option nutritionally than the traditional wholecrop approach.

Feeding crimped cereals alongside some straw if required may be better than feeding traditional wholecrop. Above: Contractor-Luke Gardner-crimping-wheat -Lancashire.
Feeding crimped cereals alongside some straw if required may be better than feeding traditional wholecrop. Above: Contractor, Luke Gardner, crimping wheat in Lancashire.

Mixed grass/legume wholecrop forages – are they worth considering? Two other options to consider are undersowing with grass/clover where the cereal is being used as a cover crop to improve establishment, or growing the cereal with a legume be that peas, beans, vetches, or even lupins. There may be some merit in the first option but, with regards to cereal/legume mixes, it is a common misconception that they produce a silage that is both high in energy and protein. They are the most difficult crop to get right both in terms of nutritive value and preservation quality and feed-out. This type of cropping regime will never produce a high energy and
high protein forage and most often it will have less than average energy and protein content compared to a good grass or grass/clover silage. The main reason for this is that the stem of the cereal will always dilute both the energy and the protein and secondly that the higher protein legume in the mixture will dilute the higher starch containing cereal and vice versa. Harvest these crops either when the: 
1. Cereal grain is soft – a very small amount of liquid is far preferable to a solid grain difficult to crush between your fingers.
2. Grain legume has a fully elongated pod that is just starting to fill.
3. Undersown grass/clover is at the correct stage of maturity for high quality silage.

Once the decision to harvest has been taken these crops require mowing, leaving a minimum of a 7.5cm but ideally 10cm stubble height. This should be followed by a rapid wilt to the optimum dry matter, which for a clamp would be 30-34% DM and for bales 35-40% DM. All these forage types should be chopped whether ensiled in a bale or clamp and for clamp silage, a maximum chop length of 5cm should be used.
It is always important to consider the additive with respect to the crop being ensiled and both the issues met during the anaerobic fermentation phase as well as the aerobic phases during filling, sealing and feed-out.

With this in mind, and breaking down the crop types mentioned above into three distinct groups for their preservation challenges, these are:
Mixed wholecrop cereal and  legume/grass mixtures.

These have significant challenges for both fermentation and aerobic stability. Fermentation due to the high buffering, high protein legume, the higher risk of soil contamination, and the potentially lower percentage dry matter content. And aerobic stability due to the straw content from the cereal portion. Therefore, these crops need an additive that can aggressively assist in controlling all aspects of ensiling. Ideally this crop needs a chemical additive that contains salts that will inhibit the clostridia and enterobacteria (sodium nitrite for instance) and the yeasts and moulds (eg sorbate and benzoate).

If producing the forage in an organic system, then a homofermentative inoculant applied at 1,000,000 bacteria/g fresh forage will control the fermentation, and to control the aerobic stability an organically-approved chemical such as citrate should do the trick.

2. Green crop cereal.
The main challenge from this crop type is fermentation, due to the high protein content and again potentially lower percent dry matter. Therefore, a good 1,000,000 bacteria/g fresh forage homofermentative inoculant product would cover these bases. If you have concerns about aerobic spoilage then the citrate approach alongside the homofermentative inoculant or a chemical salts-based additive will again assist in ensuring a good preservation process.

3. Standard pure wholecrop.
This has a big challenge from aerobic stability issues and generally few issues with fermentation. Thus, this forage type requires a chemical additive based predominantly on sorbate and benzoate salts to control the yeast and mould populations. Again, a combination product with a homofermentative 1,000,000 bacteria/g fresh forage plus an organic chemical can solve these issues on organic farms.

Many of you out there will have been told that the inoculants containing heterofermentative bacteria either alone or in a mix with homofermentative inoculants will control both the fermentation processes and the aerobic spoilage processes. These products rely on the production of acetic acid and propane-1,2-diol to control aerobic spoilage and these compounds need to be produced in sufficient quantities to control the yeast and mould populations. Frequently, they do not produce these compounds fast enough or to a high enough concentration to do their job, especially when the DM of the forage is approaching 40%. In addition, to achieve the required activity from the heterofermentative bacteria in the product they reduce the level of the homofermentative bacteria, which then results in the fermentation not being controlled sufficiently. This all results in higher dry matter losses and more importantly higher energy losses. This has been scientifically proven time and again. 

Finally: enzymes.
Enzymes as components of commercial silage additives have extremely limited evidence of any activity. This is due to a number of factors:

1. Enzymes are only active over a relatively narrow pH range and your silage is likely to be at the correct pH for a matter of a few hours.
2. Enzymes are proteins and the silo contains many proteolytic enzymes that breakdown proteins and the enzymes added as part of the inoculant will also be broken down by the plant enzymes in the silage. 3. The enzymes require water to work, so the higher the DM of the silage the less water there is so the slower they will work. 4. The enzymes are added in extremely low concentrations, and frequently in an insufficient quantity to have any meaningful effect on either the release of sugar to drive the silage fermentation or solubilization of fibre to improve digestibility.

In conclusion, please never buy a silage additive because it contains enzymes; buy it because all the other components fit what you require.

Left: Green wholecrop rye made in Yorkshire this spring replenished low forage stocks on Guy Prudom’s farm article “Early adoption of green-crop wholecropping in UK“.

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