Feed Ingredients

The term “cereal gains” here includes cereal grains, cereal by-products and distillers dry grains with solubles (DDGS). Cereal grains are used mainly to satisfy the energy requirement of poultry. The dominant feed grain is corn, although different grains are used in various countries and regions of the world. For instance, in the US, Brazil and most Asian countries corn is by far the most important energy source for all poultry feed, whereas wheat is the predominant supplier of dietary energy for poultry diets in Europe, Canada, Australia, New Zealand and the Russian Federation.  Of course, in reality, a feed manufacturer will use any grain in a poultry diet if it is available at a reasonable price. For instance, in some parts of the US and China wheat is often used in place of corn if its price is below that of corn. In Australia, sorghum is a key grain during the summer season instead of wheat, while in the Scandinavian countries barley and rye are used when these grains are at the right price. Although the amounts and types of cereal grains included in poultry diets will depend largely on their current costs relative to their nutritive values, care must be taken to avoid making large changes to the cereal component of diets as sudden changes can cause digestive upsets that may reduce productivity and predispose the birds to disease.

The quality of cereal grains will also depend on seasonal and storage conditions. Poor growing or storage conditions can lead to grains with a lower than expected energy content or contamination with mycotoxins or toxin-producing organisms such as fungi and ergots. Genetic and environmental factors also affect not only the content of nutrients in grains but also the nutritive value, which takes into account the digestibility of nutrients contained in an ingredient in the target animal.

In addition to the cereals themselves, their by-products, such as wheat bran, rice bran and DDGS, are used widely in poultry feed. Cereal by-products are typically high in fibre, or non-starch polysaccharides (NSP), which are poorly utilised in poultry and are low in ME.

Table 1. ME value and key nutrient composition of cereal grains

There are some challenges associated with the use of animal protein sources. First, food safety is the most important concern people have about the recycling of animal protein meals back through animals as feed ingredients. This is based on the links between the prion disease bovine spongiform encephalopathy (BSE – mad cow disease) and a variant Creutzfeldt-Jakob disease in humans.  Importantly for poultry production though, researchers have been unable to demonstrate the transfer of prions to poultry (Moore J et.al. (2011) BMC Res Notes. Vol.4, p.501) and no symptoms of disease have been observed in birds up to five years after direct challenges. The proteins (prions) associated with BSE are not destroyed by traditional methods of rendering and are capable of causing disease when BSE contaminated meat and bone meals are injected cerebrally into ruminants.

As a consequence of the public’s concerns about BSE, Australia does not allow the use of ruminant by-products in feed for ruminants; however, ruminant by-products are available for use in poultry feed.

In addition to BSE contamination, there are concerns that animal protein meals are responsible for food borne pathogen contamination, such as Salmonella. Typically these bacteria are destroyed by rendering and possible recontamination is often negated by pelleting of manufactured feeds. In most cases, if poultry acquire Salmonella it is likely to be from an environmental source other than feed. It is possible for animal protein meals to be contaminated with high levels of heavy metals, dioxins and PCBs (pesticides); however, meals are monitored and regulated to minimise this contamination.

Table 3. ME values Nutrient levels in selected animal protein meals

Source: adapted from Hamilton (2002)

The most accurate way of measuring the ‘feed value’ of an ingredient is to use an animal assay or bioassay. However, these assays are extremely time consuming and expensive. One of the most promising predictors of nutrient level and availability is near-infrared reflectance spectroscopy. This technology is rapidly being adopted by feed manufacturers and enables rapid screening of incoming products for a wide variety of measurements (moisture, protein, amino acid availability, fat, etc.). In most cases, the samples can be prepared, scanned and results assessed in a few minutes. However, calibrations are still being established for meals and further research is required to classify the cause of variation in feed value.

Animal protein meals have a long history in poultry nutrition. The utilisation of this valuable feed ingredient is important in minimising loss (nutrient and economic value) in the production of safe, high-quality poultry meat, eggs and bioproducts.

Table 4. ME values and nutrient composition of selected animal protein sources