Course: Feeding by-products | Last Updates: 12th October 2015
UK-produced wheat Dried Distillers’ Grains with Solubles (DDGS) and alternative cereals such as sorghum are of increasing interest as feeds.
What are Dried Distillers’ Grains with Solubles?
DDGS are a by-product left over from the making of biofuel, a process that converts wheat starch into ethanol. There are several methods of biofuel production, each having an impact on the nutrient value of DDGS. Wet distillers’ grains are of little use to the poultry industry, mainly because of storage problems.
DDGS is widely considered to be a good source of fibre and there are indications that it may improve gut health. Research has shown that every 10% of DDGS included in a poultry ration will raise crude fibre levels by 1%.
The product has some advantages compared with wheat, not least its greatly increased protein content (see table below left), because the material is concentrated during processing. While wheat averages 11%, protein levels in DDGS can be as high as 30%. The metabolisable energy (ME) is slightly higher in wheat (13MJ/kg) than in DDGS (11.2MJ/kg).
What potential do they have as an alternative feed?
With the UK lagging behind many other countries in biofuels development, significant quantities of DDGS have not yet been produced in this country, although a small tonnage has been imported from Europe. In the USA, where the market is more advanced, DDGS has caused some problems for feed compounders. Bridging and caking can occur when unloading, and concerns have been expressed over flowability and consistency.
As well as production methods causing variability in DDGS, drying processes also have an effect. Some dryers damage proteins, reducing nutrient availability and digestibility levels. Heat-damaged DDGS in the USA is generally suitable only for cattle feed.
However, recent production techniques have paid more attention to the quality of DDGS.
But despite considerable progress, DDGS variability remains a serious issue that must be overcome if the product is to develop into a viable poultry feed ingredient.
What outlets are there in the UK?
Physical availability is another important factor. The Ensus wheat refinery plant on Teesside and a second plant, to be built in Hull, are expected to produce a combined 650,000t of DDGS a year. Meanwhile, three other sites – in Manchester, Norfolk and Somerset – have also been earmarked for biofuel production.
It is worth noting that the Teesside and Humberside plants will each require about 1m tonnes of wheat a year. This new market will ultimately affect the quantity of wheat available for export and may affect some domestic cereal prices.
It is probable that if DDGS is adopted as a standard feed for the poultry industry, its use is likely to be limited to layer and turkey diets. Its high protein, relative to digestible lysine content, makes it less suitable for broiler diets, where the general aim is to minimise crude protein levels to maintain litter quality.
It is difficult to predict future prices for DDGS because its worth hinges on its value relative to other raw materials.
Once DDGS becomes readily available, the poultry industry will face direct competition from the pig and cattle industries. Like any other raw material, transport costs have to be taken into account.
Proximity to bioethanol processing sites may turn out to be an advantage in the future. But the main priority is to develop a validation process for the nutrient value of DDGS – and, indeed, all alternative feeds – and find a quick and cost-effective way of testing products by the load.
What about glycerol?
Glycerol, another by-product of biofuel (diesel) production, is a liquid that contains about 50% of the energy content of fats and oils. With an ME of about 17MJ/kg, it is a highly digestible feed ingredient for poultry.
However, the product poses considerable handling difficulties. Glycerol is suitable for inclusion in pellets because it binds materials together, improving pellet quality. But its viscous qualities prevent it from flowing when added to feed in a mixer. It has been tried in UK broiler and layer diets in the past, but was found to cause feed handling problems.
Glycerol has been successfully introduced into some European poultry diets, but we need to learn from their experiences about how to handle it in the mill.
Procurement is another hurdle. To develop systems capable of handling glycerol, we would need it to be available in much larger quantities. But if these problems can be solved, it could become popular as an ingredient for broilers, turkeys and layers.
Do rapeseed by-products hold potential?
Rape expeller is a by-product of a biodiesel manufacturing technique that uses oilseed rape. Although it is high in protein at 30%, little research has been carried out on its suitability for poultry diets. Production methods use a cold pressing process, so there is no risk of heat damage affecting proteins.
Despite considering that rape expeller meal could be included in broiler, turkey and layer diets in the future, there are concerns about oilseed rape by-products being fed to poultry. This is because the breakdown of chemicals in the seed can adversely affect growth rates and egg production.
Growers producing rape for biodiesel are mainly concerned with achieving high yields, a factor that might encourage them to use high glucosinolate varieties. However, meal with a high level of glucosinolates is not suitable for poultry. Therefore, traceability and quality control are very important.
A recent scientific breakthrough could lead to oilseed rape and associate products gaining importance.
A small proportion of eggs from birds fed with rape products have a ‘fishy’ taint. But experts have now identified the gene responsible for a bird’s inability to handle oilseed rape and its by-products.
Meanwhile, the poultry industry is waiting for biofuel production to be embraced on a larger scale, because current production levels would severely limit availability. In general, rape expeller is produced in a few small plants, creating problems with quality variability and transport.
Is sorghum viable in the UK?
Sorghum, a cereal grain grown primarily in Africa and the USA, might be useful as a wheat replacer, but only if prices are set at a competitive level. At present, the crop is too expensive, but the situation could change because sorghum growers are thought to be looking to export their product to Europe.
Sorghum will need careful assessment before it is used. Varieties from Africa tend to have high tannin levels because of their resistance to pests. But this type of ingredient feed is not desirable in poultry feed because high tannin levels reduce nutrient digestibility.
Sorghum from the USA, however, is generally sold on the basis of guaranteed low tannin, and the material has been used successfully for the first six months of this year, when wheat prices were high. As with all commodities, sellers are well aware of the opportunity value of formulations and, as such, will need to be priced accordingly, to make them attractive in the UK again.
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