NUTRITION ▶▶▶
Six nutritional considerations when feeding DDGS to layers
BY CARLOS DE LA CRUZ T
he greatest challenge in using DDGS in pullet and layer diets is working with accurate nutrition matri- ces. The nutritional composition and quality differ substantially between sources of DDGS. For exam-
ple, the conditions during the drying process have a huge im- pact on amino acid digestibility. DDGS users are often tempt- ed to use colour as an indicator of DDGS quality, with energy and protein levels as the main criteria applied to decide whether or not to use it. However, there are also other as- pects to consider when birds are fed DDGS.
• Amino acid digestibility Visually we can gain a rough idea of the effect of heat dam- age on DDGS: a darker colour indicates overheating and thus reduced protein quality and lower amino acid digestibility. However, visual inspection with the human eye is subjective and heat damage is not the only factor which can affect col- our. DDGS will also be influenced by the maturity of the grain, the amount of solubles added, storage conditions, the pres- ence of toxins, contamination with sand, as well as the possi- ble use of insecticides or fungicides which will give it a dull and dusty appearance. DDGS contains proteins and carbohydrates which when ex- posed to high temperatures during the drying process can produce a chemical reaction (Maillard reaction) that affects the digestibility of its amino acids. Thus, more reliable heat damage indicators than just colour are needed to evaluate quality. The amino acid Lysine is very susceptible to heat damage and the Maillard reaction. The reactive Lysine assay is very specific and measures only that amount of Lysine which did not take part in any Maillard reaction and is therefore po- tentially available to the animal. Reactive Lysine is an excel- lent indicator for heat damage and correlates well with changes in amino acid digestibility. Classically, the reactive Lysine assay is a very demanding wet chemistry method. Today however, Near-infrared Spectrosco- py (NIR) techniques are available that can determine the
At inclusion rates of 3-5% for growing pullets and up to 15% for layers, DDGS (Distillers’ Dried Grains with Solubles) is an excellent feedstuff. A good quality DDGS is high in energy and amino acid content and free from anti-nutritional factors such as mycotoxins. DDGS supports good egg production and egg quality.
amount of reactive Lysine and thus estimate the degree of heat damage. Based on this estimation amino acid digestibili- ty can be corrected. To summarise: NIR now provides a useful and powerful tool to identify and evaluate heat damage in DDGS giving reliable information on actual protein and ami- no acid quality.
• Phosphorus availability Although there is consistent evidence that excessive heating (dark colour) during DDGS drying reduces the digestibility of amino acids, it may increase the relative bio-availability of phosphorus for poultry. Studies suggest that the fermentation process which the corn undergoes improves phosphorus avail- ability in the by-product. The synthesis of microbial phytase during fermentation and structural changes caused by the drying process may increase phosphorus bio-availability.
DDGS users are often tempted to use colour as an indicator of DDGS quality, with energy and protein levels as the main crite- ria to decide whether or not to use it.
▶ ALL ABOUT FEED | Volume 28, No. 6, 2020
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PHOTO: PETER JUNGHNEL
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