DDGS: Cheap and Nutritious Food for Poultry

The world grain price is increasing day by day and the industry is facing several challenges to produce good quality animal products with reasonable price for consumers. Similarly, poultry industry in Bangladesh is also fighting with this high grain price to maintain their production with marginal profit. Small and medium poultry farm owners are mainly affected and losing their capitals investment in this sector. The increased cost and the limited supply of conventional grains have necessitated for focusing research and extension efforts towards the potential utilization of energy and proteins from several grain by-products which are cheaper with high nutritive values. Corn distillers dried grains with solubles (DDGS) can play a vital role in this high grain price situation to formulate the least cost diets for poultry. DDGS is a co-product of ethanol production plants that use corn for manufacturing. During the yeast fermentation in ethanol plants, corn is ground, mixed with water, cooked and the liquefied starch from this process is hydrolyzed and fermented to produce ethanol and CO2. As a result the non-fermentable components of this process which are rich in essential nutrients such as protein, fat, fiber, vitamins and minerals are recovered in a highly concentrated form as distillers dried grains with solubles. Although distillers dried grains have been used by the poultry industry for some time, recently a renaissance in the use of DDGS has been observed in the US and also around the world. This is due to the rapid escalation in its production as well as its improved quality when derived from the new generation ethanol plants. Therefore, in the light of the large production of corn DDGS entering the US and other overseas markets, the aim of this topic is to provide a compendium of information to the people involved with the industry regarding nutritional value of corn DDGS for poultry.

Nutrient contents and availability of DDGS for poultry

Corn DDGS contain all the nutrients from grain in a concentrated form except for the majority of the starch, which has been utilized in the fermentation process. Therefore, it can be a rich source of crude protein (CP), amino acids, P and other nutrients in poultry diets. Reliable values for the nutrient content of feed constituents are essential to create more precise diet formulations for poultry.

A. Metabolizable energy content

Several studies provide estimates of the metabolizable energy (ME) content of DDGS for poultry. Lumpkins et al. (2004) reported that the TMEn content of a single DDGS sample was 2,905 kcal/kg. In a later study, the same group determined the TMEn content of 17 different DDGS samples representing products from six different ethanol plants. They determined that the TMEn contents ranged from 2,490 to 3,190 kcal/kg with a mean value of 2,820 kcal/kg and an associated coefficient of variation of 6.4% (Batal and Dale, 2006). Fastinger et al. (2006) concluded that the TMEn content of DDGS averaged 2,871 kcal/kg and had considerable variation among the samples. Furthermore, a large variation in TMEn values of DDGS were also reported by Parsons et al. (2006), who determined the mean TMEn value of 20 DDGS at 2,863 kcal/kg ± 224 kcal/kg. It was hypothesized that energy in corn DDGS would not vary if samples were derived from ethanol plants using similar production technologies and corn that is grown in a proximate geographical location. Therefore, nutritionists should be cautious of the fiber content and sources of data for DDGS ME values, as well as energy variability when formulating diets for poultry.

B. Amino Acid content

Dale and Batal (2005) reported that CP content of corn DDGS can vary from 24 % to 29 %. In our laboratory we assessed CP content on 395 corn DDGS samples imported to Korea from the US, and the average CP content was 27.15 % (23.87-30.41) with 3.72 % coefficient of variation. Batal and Dale (2006) found that CP content of DDGS ranged between 23 % and 32 %. Spiehs et al. (2002) have evaluated nutrient level of DDGS originating from 10 new ethanol plants in Minnesota and South Dakota, and also found that the CP accounted for 30.2 %, and lysine and methionine for 0.85 % and 0.55 %, respectively. The high variability among DDGS sources was found mainly for the two limiting amino acids for poultry, lysine and methionine. Reese and Lewis (1989) showed that corn produced in Nebraska in 1988 varied in CP from 7.8 to 10 %, and 0.22 to 0.32 % in lysine content. Differences in production technology provide almost as much variation within one source of corn as there is between different plants. Parsons et al. (1983) conducted five trials that aimed to evaluate the protein quality of DDGS and concluded that when DDGS is fed to growing chicks as the sole source of dietary protein, tryptophan closely followed by arginine are the second and third limiting amino acids respectively, after lysine. Although DDGS was limiting in tryptophan and arginine it was found that the overall protein quality of DDGS could be improved greatly by lysine supplementation for growing chicks.

C. Mineral composition

A laboratory analysis of corn DDGS from the US showed that DDGS can be a good source of P (0.76 %), Zn (57.26 ppm), K (0.91 ppm), and other minerals. Phosphorus content in DDGS has been reported at 0.72 % and varies widely from 0.48 to 0.91 %. Similarly, Spiehs et al. (2002) reported the P variation in DDGS ranged from 0.59 to 0.95 %. This large difference in P content derives partially from its variation in corn grain and amount of starch residue in DDGS. However, the technological process of ethanol production can also significantly contribute to its content and variation. It has been suggested that the total P content may be even higher than 0.72 % in some sources of DDGS if produced in new ethanol plants. Moreover, the rate of addition of solubles to the wet grains prior to drying affects the P content, because the solubles contain more than three times as much P as do the wet grains.

D. Pigments content

Corn grain contains about 20 ppm of xanthophylls and it is expected that corn DDGS may by a good source of xanthophylls pigment, due to their concentration of the pigment during the production process. However, the actual xanthophylls content may be lower in DDGS because of heat destruction during drying. Roberson et al. (2005) analyzed two DDGS samples and observed 29.75 ppm of xanthophylls in one of the samples, but only 3.48 ppm in another, dark colored sample which was considered to be heat damaged. By analyzing 16 samples of DDGS deriving from US in our laboratory, we showed that the average concentration of carotene and xanthophylls was 8.58 and 36.72 ppm, respectively. Since the typical corn and soybean-based commercial poultry diet does not supply the necessary amount and type of xanthophylls to produce the deep yellow color in the egg yolk and skin, DDGS can be a good source of these pigments as long as they have not been overheated during the production process.

E. Other nutrients

DDGS is not only a good source of energy, amino acids and minerals but also can be a rich source of water soluble vitamins and other nutrients that are present in the corn used for the ethanol production. D’Ercole et al. (1939) reported that DDGS is a good source of riboflavin and thiamine. DDGS also contain some biologically active substances such as nucleotides, mannan oligosacharides, β-1, 3 or 1, 6 glucan, inositol, glutamine and nucleic acids, which have a beneficial effect on immune responses and the health of animals. Therefore, to reduce the feed cost and to make a balanced diet for poultry, DDGS would be a viable alternative energy grain source for the feed industry in Bangladesh.

DDGS: Cheap and Nutritious Food for Poultry

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