Maximizing Livestock Nutrition: The Role of Rice Distiller’s Dried Grains with Solubles (rDDGS)

Dr.Sudhir Kale, Dr.Sushant Labh, Dr. Dilip L. Waghmare
Kemin Industries South Asia Pvt Ltd
JAPFA COMFEED INDIA PVT. LTD

Introduction

In poultry nutrition, searching for alternative feed ingredients is a continuous process in pursuing economical poultry production. Feed is the major constituent in poultry production accounting for 65-75% of total production cost. The cost of protein sources primarily drives feed costs. One of the ways to reduce cost is the substitution of expensive protein sources with lower-cost ingredients. Therefore, efforts are being made to reduce the cost of production by employing alternative feed ingredients in the broiler chicken ration.

Distiller’s dried grains with solubles (DDGS) are by-products of the ethanol industry produced by dry milling. Corn, wheat, sorghum, barley, and rice can be used for ethanol production, which can be used as an alternative plant protein source. The non-fermentable components of the grains which are rich in nutrients like protein, fat, fiber, vitamins, and minerals are recovered in a highly concentrated form as DDGS. Its inclusion in poultry has many advantages including wide availability, adequate protein level, and complementary amino acid profile.

DDGS contains microbial phytase, which improves phosphorus bioavailability. It also contains yeast biomass (6%) which helps in building the immune system stimulation and gut development⁴. DDGS has a beneficial effect on the environment, as it mitigates the harmful emissions and pollution from manure and provides a clean atmosphere.  However, the use of DDGS in poultry has limitations because of variations in its characteristics (Physical, chemical, and Nutritional) and digestibility among the sources⁵. The nutrient composition of DDGS varies depending upon the source of grains, the method and machinery used for ethanol production, and the rate of condensed distillers’ soluble (CDS) addition. The DDGS types available in India are rice, bajara, barley, corn, wheat, and sorghum DDGS. Among all Rice DDGS is predominant and available in more quantity.

Physical characteristics

Physical characteristics vary among the sources and impact their feed value and inclusion level in the diet. Physical character includes color, smell, particle size, bulk density, flowability, pH, shelf-life stability, and hygroscopicity.

Color

The color of DDGS can vary from light yellow to dark brown. The color difference is influenced by the color of source grains, and the rate of soluble addition (time and temperature). When the relatively high portion of CDS is added to make DDGS, the color becomes darker

Smell

Fresh Rice DDGS smells sweet and fermented where a charred and smoky smell is an indicator of poor quality or overheated material.

Particle size

The particle size of good quality RDDGS should be uniform in distribution and should allow easy and good mixing with other raw materials used in feed manufacturing.

Moisture and pH

Moisture content is the deciding factor of storage stability of RDDGS. Maximum content should be within 12% where there is a high chance of more mycotoxin and rancidity development. The pH of RDDGS is 4.1, the lower the pH, the lower the chance of bacterial contamination.

Chemical composition

DDGS is very low in starch but higher in non-starch polysaccharides (NSP) content as compared to their parent grains used. DDGS is higher in gross energy than parent grain. DDGS contains all the nutrients from grain in a concentrated form and the majority of starch has been utilized in the fermentation process during ethanol production. This will concentrate all nutrients about three-fold present in the cereal since two-thirds to three fourth portion of cereal content is starch. The nutrient composition of Rice DDGS (RDDGS) varies depending on the source of grain and the methods of RDDGS production.

From 01^st Jan 2024 to 30^th  June 2204, we analyzed 94 samples from different suppliers and different regions. Herewith, we have given average values for different regions.  (Data given in two different Tables, 1 – Proximate analysis, Table  2  Amino acids analysis, Table 3  Amino acid data in different studies)

1. Crude protein

Various studies reported a crude protein content between 44 % to 45 % in RDDGS. A high crude protein content of 61.41 % in RDDGS was reported and a low crude protein content of 28.55 % in RDDGS was also observed^5,6.  This variation is mainly due to variations in the chemical composition of raw material used, differences in fermentation efficiency, and processing techniques. Thus nutritionists need to characterize the composition of these nutrients of RDDGS by a standardized protocol before formulating balanced diets for poultry. Although measuring the color score of DDGS may provide a rapid indication of the general quality of DDGS, it has to be exercised with caution as it is not a precise estimation of the nutrient content.

1. Crude fiber and Ether extract

The range of crude fiber was 1.23 to 5 and ether extract content was 3.19 to 7.67 %. A crude fiber content (4.89 to 10.85 %) and ether extract (2.24 to 8.90 %) were also reported in some studies ^2,6.

1. Energy

The ME (Metabolizable Energy) levels in RDDGS vary from 2200 kcal/kg to 2400 kcal.kg^.

Mineral composition

Rice DDGS can be a good source of P (0.76%), Zn (57.26 ppm), K (0.91 ppm), and other minerals. The level of these minerals varies based on various factors but similarly, their bioavailability is also linked with the source, the ethanol production process. So level of all these minerals needs to be analyzed and quantified before considering into feed formulation to avoid the effect on birds performance. Also, total Sulphur content needs to be confirmed as during ethanol production addition of sulphuric acid is done to maintain the pH. Sulphur levels in poultry above 0.6% produce wet litter and 1.2 % Sulphur produces ill health effect.

Amino acid composition of RDDGS

RDDGS contains all the nutrients from grain in a concentrated form and the majority of starch has been utilized in the fermentation process during ethanol production. The amino acid profile of RDDGS showed lower lysine (0.64 – 1.23 %) content than soya bean meal (2.99 – 3.22 %) and the other amino acids were well within the range. This phenomenon may be due to variations in the amino acid composition of the parent grains used for ethanol production, compared with soya protein amino acid profile². The variation in the nutrient content is related to the drying process, uneven mixing of CDS during the drying process which will result in a change in nutrient variability in DDGS, and due to high temperature, which may reduce the protein quality.

Other Nutrient of Rice DDGS

There is very few data available in the literature about the content of Rice DDGS, but data available on DDGS can be considered as a reference for the same⁵.

DDGS is a good source of riboflavin and thiamine and most of the riboflavin in DDGS comes from the soluble fraction. DDGS also contain some biologically active substances such as nucleotides, mannan oligosaccharides, 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.

Corn grain contains about  20  ppm of xanthophylls and it is expected that corn  DDGS may be a good source of xanthophylls (lutein and zeaxanthin)  pigment,  due to their concentration of the pigment during the production process.  However,  the actual xanthophyll content may be lower in  DDGS because of heat destruction during drying.

Mycotoxin in Rice DDGS

Generally, the risk of mycotoxin contamination of DDGS is very low because of the implemented surveillance system at various points from the farm through ethanol plants to animal feed^2,5. Many ethanol plants routinely monitor incoming corn and reject contaminated deliveries. However, to secure the rapidly growing biofuel industry and efficient utilization of its by-products multiple strategies have been implemented to control the quality of DDGS. Rotation of corn with other crops, proper handling, and storage of rice, constant monitoring of moisture and temperature as well as insect control are the basic methods employed in mycotoxin control. Moreover, the production of genetically engineered rice varieties that are directly resistant to various diseases and mycotoxins, as well as transgenic insect-resistant corn that is indirectly less susceptible to insect damage and consequently mycotoxin accumulation, has been well advanced.  Despite all the risk factors associated with DDGS, mycotoxin is on top, as all starch undergoes fermentation during the ethanol production process hence mycotoxin content goes 3 to 4 fold. Major mycotoxins in parent rice include Aflatoxin, Ochratoxin, T2, and Fumonosin^5,6. Along with the mycotoxin, Malathion (up to 50 ppb) was also found in some of the DDGS samples (Table 4 summarises mycotoxin analyzed in samples collected from a different region of India, from 1-Jan 2024 to 30^th June -2024).

Table 4: Avg toxin values for all analyzed samples.

Production statistics, industry scenario, and composition of Corn vs Rice DDGS

Data on  Production statistics, industry scenario, and composition of Corn vs Rice DDGS is given in Tables 5, 6, and 7)

Table 5: Ethanol Production and Blending Trends- Year-Wise

Table 6:  Starch content and ethanol yield of various feedstocks

Table  7:  Comparison of common bio-fuel co-products

Optimization of feed cost by Rice DDGS inclusion:

Soya DOC has more lysine and low methionine whereas Rice DDGS contains more methionine and low lysine. So, both are complementary to each other when used with all caution. The current price of Rice DDGS varies from 15 to 20 Vs the price of soya DOC 45 vs 49. So, considering the per unit of nutrient cost in Rice DDGS, it is a very good alternative, without compromising quality.

Steps to follow while formulating Rice DDGS in feed formulation

1. Storage condition  Storage of rice DDGS mainly depends upon the initial level of moisture, season and storage area, and type of packaging material.
2. Physical examination Physical parameters like pH, moisture, and mycotoxin level need to be considered.
3. Proximate analysis  Detailed analysis of parameters like crude protein, crude fiber, moisture, ether extract, and amino acid need to be done before formulating a diet.
4. Maximum inclusion level in feed  Maximum inclusion level of Rice DDGS is dependent upon factors like age of birds, daily feed consumption, breed, season, inclusion level of other raw material and price, environmental factor, and disease scenario in the area. In addition to this maximum inclusion level depends on diet density, age, and breed of birds. In the case of a low-density diet, inclusion should not go to a higher level because of variations in nutritional composition. DDGS can be used safely up to 6-8% broiler and layer diet.

 Target organ protection

5. 1. Considering overall risk and threat factor protection against target organs like Liver, Kidney, Bursa, and Gut health needs to be considered. Sufficient levels of biotin, choline, and methyl donors need to be considered for liver health. To maintain immune status good quality toxin binder with multi-toxin binding and pesticide binding potency should be used in feed formulation.
   2. To have complete gut health protection probiotics having activity against Clostridium spp., Salmonella , and E. coli species are needed.
   3. Considering variations in nutrient profile like Crude protein, Amino acid level and digestibility, ME content, and bioavailability of P, the use of a combination enzyme is the best strategy to tackle economic and nutritional variation challenges.

Enzyme solution having xylanase, amylase, beta gluconase, cellouse, amylase, and multiprotease should be used. The use of a combination of enzymes not only helps to reduce the cost but also helps to mitigate the risk of anti-nutritional factors. It also helps to release extra sugar by breaking other NSP components like beta-glucan, mannan, and oligosaccharides.

Risks of using ‘static’ published databases

The nutrient composition of feed ingredients changes over time. Therefore, relying on “static” published book values from old, published databases can lead to significant over- or underestimation of actual energy and nutrient content of commonly used feed ingredients. This is even more critical for DDGS because the nutrient composition continues to change as ethanol plants adopt new processes to improve ethanol yield, extract more corn oil, and enhance protein and amino acid content. Therefore, when determining appropriate and accurate nutritional values for DDGS, it is important to consider the dates of publications and current actual data to compile these databases because the nutrient composition began changing when the ethanol industry objective, need, and process changed⁷.

Summary:

Biofuel Co-Products are cheaper, lowering the cost of feed for animals and reducing potential threats to the environment. The Government of India has announced an ethanol blending program of up to 20 % in petroleum.  In this regard, a greater number of distillers will produce ethanol from sugarcane, maize, rice, sorghum, and wheat. Amino acid level and digestibility, Metabolizable energy content, and bioavailability of Phosphorus (P) are the predominant factors that affect the suitability of DDGS in feed formulation. Variations in the manufacturing of ethanol production, quality of parent grain, and other associated factors need to be taken into consideration. Maximum inclusion of DDGS in feed formulation solely depends on raw material quality and nutritionist knowledge about risk factors. Rice DDGS has many advantages like better feed intake and feed Conversation Ratio. It has a good impact on egg, and meat quality due to high-omege 3-fatty acid. It improves the phosphorous bioavailability and therefore less phosphorous excretion prevents environmental pollution.

The DDGS usage comes with potential constraints of Sulphur toxicity. In the ethanol production process, sulphuric acid is used and ethanol by-products may be high in sulfate, which hamper the oxidative processes in nerve tissue, along with that risk of mycotoxin can be expected always.