Nutritional and biochemical evaluation of rice distillers dried grains with solubles (RDDGS): Chemical composition, metabolizable energy estimation, and growth performance in broiler chickens

Introduction

Poultry production systems are largely dependent on cereal grains and oilseed meals, and therefore, improving the efficiency of nutrient utilization from these ingredients is essential for sustaining production systems. Increasing emphasis is being placed on the utilization of agro-industrial coproducts, which are not directly suitable for human consumption but can be effectively converted into high-value animal protein through poultry. The rising cost and fluctuating availability of conventional protein sources, particularly soybean meal, have

The present investigation was therefore undertaken to evaluate the chemical composition of RDDGS, estimate its metabolizable energy, examine its effect on broiler growth performance, and identify an appropriate inclusion level in practical feeding systems.

Materials and Methods Ethical Approval

The experimental protocol involving broiler chickens was conducted in accordance with institutional guidelines for the care and use of animals in research. The study was reviewed and approved by the Institutional Animal Ethics Committee (IAEC), Madras Veterinary College, Chennai, India (IAEC No.: 17/SA/IAEC/2022). All procedures were carried out ensuring minimal stress and optimal welfare conditions for the birds.

Basis of Nutrient Expression

In the present study, all compositional and energy values of rice distillers dried grains with solubles (RDDGS) were expressed on a dry-matter (DM) basis to accurately represent intrinsic nutrient density and allow comparison with conventional feed ingredients. However, ingredient composition of experimental diets, calculated nutrient composition, and biological performance parameters were expressed on an as-fed basis, consistent with standard poultry feeding practices.

Sample Collection and Chemical Analysis

Eight RDDGS samples were collected from feed ingredient suppliers located in Telangana and Tamil Nadu. These samples were analyzed for chemical composition at the Animal Feed Analytical and Quality Assurance Laboratory (AFAQAL), Namakkal, following AOAC (2005) procedures. Amino acid profiling was carried out at SGS Laboratories, Ambattur, Chennai.

The following parameters were determined:  Moisture content (oven drying method)  Crude protein (Kjeldahl nitrogen × 6.25)  Ether extract (Soxhlet extraction)  Crude fiber (acid-alkali digestion)  Total ash (muffle furnace combustion)  Acid insoluble ash  Calcium and phosphorus (titrimetric/spectrophotometric methods)  Gross energy (bomb calorimetry)

The formulation batch used in diet preparation contained 16.71% moisture (83.29% DM). All nutrient values were converted to dry-matter basis.

Birds, Experimental Protocol, and Diet

Four experimental diets were formulated with RDDGS inclusion levels of 0%, 5%, 10%, and 15%, replacing soybean meal. All diets were designed to be nearly isocaloric and isonitrogenous in accordance with BIS (2007) [2] recommendations. The ingredient composition and calculated nutrient values are presented in Tables 1 and2. A total of 144 day-old straight-run commercial broiler chicks (Vencobb 400) were procured and randomly assigned to four treatment groups, each with three replicates of 12 birds.The experimental period lasted 42 days and was divided into three feeding phases: pre-starter (0-7 days), starter (8-21 days), and finisher (22-42 days). Standard management practices were followed, and feed and water were provided ad libitum.

Data Collection Body Weight (BW)

Body weight of birds was recorded: At day-old Weekly thereafter Values were expressed in grams (g).

Body Weight Gain (BWG) BWG = Final body weight-Initial body weight Calculated weekly and cumulatively.

Feed Intake (FI)

Feed intake was measured daily and expressed as: FI = Feed offered-Feed left over Values were aggregated weekly.

Feed Conversion Ratio (FCR)

Body weight gain (g) Mortality-adjusted FCR was calculated where applicable

Economic Parameters

 Feed cost per kg feed  Feed cost per kg live weight These were calculated based on ingredient cost and feed intake.

Estimation of Metabolizable Energy

Metabolizable energy (ME) of rice distillers dried grains with solubles (RDDGS) was estimated from gross energy (GE) using an ingredient-specific conversion coefficient. Gross energy was determined using a bomb calorimeter and expressed on an as-fed basis. For comparison of nutrient density, ME was also expressed on a dry-matter basis (DM = 82.86%), giving an estimated value of 3554 kcal/kg (DM basis). The use of a coefficient of 0.72 accounts for reduced energy availability in distillers coproducts due to higher fiber content and heat-induced reductions in nutrient digestibility (Rochell, 2018) [20] .

Results

Chemical Composition of RDDGS (Dry Matter Basis)

Chemical Composition of RDDGS are presented in Table 3.

The compositional analysis of rice distillers dried grains with solubles (RDDGS) indicated that the ingredient is nutritionally concentrated, particularly when interpreted on a dry-matter basis. The mean crude protein content was recorded as 43.57%, which increased to approximately 52.54% when corrected for moisture content. The coefficient of variation for crude protein was relatively low (6.77%), suggesting consistency in protein concentration across samples. In contrast, crude fiber exhibited substantial variability, with a coefficient of variation exceeding 50%. This wide range reflects differences in raw material composition and processing conditions. Ether extract and total ash also showed moderate variation, indicating variability in lipid content and mineral fractions among samples. Gross energy values remained relatively stable, with a low coefficient of variation (1.83%), suggesting that the energy content of RDDGS is comparatively consistent despite variation in other proximate components. The estimated metabolizable energy, derived using an ME:GE coefficient of 0.72, followed a similar pattern of low variability.

Amino Acid Profile

Amino Acid Profile of RDDGS are presented in Table 4.

The amino acid profile revealed that RDDGS protein is imbalanced, with relatively low lysine content compared to other essential amino acids. This limitation becomes more evident when expressed on a dry-matter basis, indicating that protein quality is constrained despite high crude protein levels.

Body Weight

Body weight data are presented in Table 5. Body weight measurements did not differ significantly among treatments at the day-old stage (p>0.05), indicating uniformity in initial chick weight. During the first week, birds in the 5% inclusion group (T 2 ) maintained body weight comparable to the control group, whereas those in higher inclusion groups (T 3 and T 4 ) exhibited reduced weights. From the second week onwards, a progressive decline in body weight was observed with increasing levels of RDDGS inclusion. However, by the fifth and sixth weeks, birds in T 2 demonstrated body weights comparable to the control, suggesting that low-level inclusion did not adversely affect long-term growth. In contrast, birds in T 3 and T 4 continued to show significantly lower body weights (p<0.01).

Sex-wise Performance

Sex-wise analysis (Table 5A) showed no significant differences during early growth stages (p>0.05). However, significant differences were observed during weeks 5 and 6 (p<0.01), with males exhibiting higher body weight and weight gain compared to females. These results indicate a main effect of sex on late growth performance.

Body Weight Gain

Weekly Body Weight Gain presented in in Table 6.

The pattern of body weight gain mirrored the trends observed in body weight. Birds receiving 5% RDDGS showed gains comparable to the control group during later stages, whereas higher inclusion levels resulted in significantly reduced gains throughout the experimental period. The reduction in weight gain at higher inclusion levels suggests a limitation in effective nutrient utilization, despite the high crude protein content of the ingredient.

Feed Intake

Cumulative Feed Intake presented in Table 7.

Feed intake remained comparable between T 1 and T 2 during the later stages of the experiment. However, a noticeable decline in feed intake was recorded in T 3 and T 4 from the second week onwards. This reduction became more pronounced as the level of RDDGS increased. The decrease in feed intake indicates that factors such as increased dietary bulk or palatability may have influenced voluntary consumption.

Feed Conversion Ratio (FCR)

Cumulative Feed Conversion Ratio of Broilers Fed Different Levels of RDDGS in Table 8. Feed conversion ratio (FCR) values varied across treatments. During the early phase, some variability was observed, likely due to low feed intake and small differences in initial growth. From the second week onwards, a consistent pattern emerged. Birds in T 2 maintained FCR values comparable to the control group, whereas those in T 4 consistently showed poorer FCR. Birds in T 3 exhibited intermediate values. The cumulative FCR at the end of the trial confirmed that feed efficiency was maintained at 5% inclusion but deteriorated at higher levels.

Economic Analysis

Feed Cost and Economic Efficiency of Broilers Fed Different Levels of RDDGS in Table 9.

Feed cost per kilogram of feed decreased progressively with increasing levels of RDDGS inclusion. Similarly, feed cost per kilogram of live weight gain showed a decreasing trend, with the lowest value observed in T 4 .However, when considered alongside growth performance, it became evident that the reduction in cost at higher inclusion levels was associated with compromised biological efficiency.

Discussion

Nutritional characteristics of RDDGS

The high crude protein content observed in RDDGS reflects the concentration effect resulting from starch removal during fermentation. Similar observations have been reported in distillers coproducts, where protein, fiber, and lipid fractions become concentrated after ethanol extraction (Loar et al., 2010) [16] . Despite this high protein concentration, the variability observed in fiber and ash content indicates that the ingredient is not compositionally uniform. Such variability has important implications for diet formulation and nutrient availability.

Amino acid limitation

Although crude protein levels were high, the biological performance results indicate that protein quality may be limiting. In particular, lysine availability is known to be reduced in distillers grains due to heat processing, which affects digestibility (Rochell, 2018) [20] . This limitation becomes more pronounced at higher inclusion levels, where the cumulative effect of amino acid imbalance likely contributes to reduced growth performance.

Growth response

The growth pattern observed in the present study suggests a threshold effect. Birds receiving 5% RDDGS were able to maintain growth performance comparable to the control, whereas higher inclusion levels resulted in reduced body weight and weight gain. This response is consistent with earlier findings that moderate inclusion of DDGS can be tolerated, but higher levels may impair performance if nutrient balance is not adequately maintained (Loar et al., 2010) [16] .

Feed intake

The reduction in feed intake observed at higher inclusion levels is likely associated with increased dietary fiber.

Poultry have limited ability to utilize fiber, and increased fiber content may lead to reduced feed intake due to gut fill effects and slower passage rate (Rochell, 2018) [20] . Additionally, fermentation-derived compounds may influence palatability, further contributing to reduced consumption.

Feed Conversion Ratio

The deterioration in FCR at higher inclusion levels indicates reduced efficiency of nutrient utilization. This may be attributed to a combination of factors, including reduced digestibility, amino acid imbalance, and lower metabolizable energy availability. The maintenance of FCR at 5% inclusion suggests that the ingredient can be effectively utilized at lower levels without compromising feed efficiency.

Economic considerations

Although feed cost decreased with increasing RDDGS inclusion, the associated decline in growth performance at higher levels limits its economic advantage. The optimal inclusion level must therefore balance cost reduction with biological efficiency. In the present study, 5% inclusion provided the most favorable balance between these factors.

Conclusion

Rice distillers dried grains with solubles (RDDGS) is a nutritionally concentrated ingredient when evaluated on a dry-matter basis. However, its utilization in broiler diets is influenced by amino acid balance and fiber content. Inclusion at 5% did not adversely affect growth performance, feed intake, or feed conversion ratio, whereas higher inclusion levels resulted in reduced performance. From both biological and economic perspectives, RDDGS can be safely incorporated up to 5% in broiler diets when appropriate nutrient balancing is ensured.

Acknowledgement

AcknowledgementThis research was funded by Department of Poultry Science, Madras Veterinary College, Tamil Nadu Veterinary and Animal Science University, Chennai-600 007, Tamil Nadu, India.

References

1. Association of Official Analytical Chemists. Official Methods of Analysis. 18th ed. Washington (DC): AOAC; 2005.
2. Bureau of Indian Standards. Nutrient Requirements for Poultry (IS 9863). New Delhi: BIS; 2007.
3. Choi HS, Lee HL, Shin MH, Jo C, Lee SK, Lee BD. Nutritive and economic values of corn distiller's dried grains with solubles in broiler diets. Asian-Australas J Anim Sci. 2008;21(3):414-419.
4. Dang PK, Giang NT, Nguyen TT, Chu-Ky S. Effects of dietary level of rice distiller's dried grains on performance and meat quality of chickens. Indian J Anim Res. 2018;1(5):[page range].
5. Dinani OP, Tyagi PK, Mandal AB, Tyagi PK, Dutta N. Evaluation of feeding value of rice-based distillers dried grains with solubles (DDGS) for broiler chickens. Indian J Anim Res. 2019;53(7):901-906.
6. Dinani OP, Tyagi PK, Mandal AB, Tyagi PK, Tyagi JS, Popat DS. Effect of feeding rice-based distillers dried grains with solubles (rDDGS) on haematological, serum biochemical and carcass traits in broilers. Int J Pure Appl Biosci. 2018;6(2):1085-1090.
7. Dingore AD. Effect of feeding different levels of rice distillers dried grains with solubles (RDDGS) on performance of broilers [MVSc thesis]. Nagpur: MAFSU; 2015.
8. Gupta S. Feeding value of rice-based dry distiller grains with solubles in white leghorn layers [PhD thesis]. Izatnagar: IVRI; 2017.
9. Gupta SL, Tyagi PK, Tyagi PK, Mandal AB, Mir NA, Sharma M. Feeding value of rice-based dry distiller grains with solubles in white leghorn layers. Int J Poult Sci. 2016;15(7):214-225.
10. Khose K, Manwar S, Dhore R, Kuralkar S, Waghmare S. Feeding corn distillers dried grains with solubles and enzyme supplementation on performance of broiler chicken. Int J Livest Res. 2017;8(5):313-318.
11. Khose KK, Manwar SJ, Joshi MV, Kuralkar SV, Gole MA, Wade MR. Effect of dietary rice distillers dried grains with solubles and enzyme supplementation on growth performance and immune status in broiler chickens. Indian J Poult Sci. 2021;56(2):115-121.
12. Kramer CY. Extension of multiple range tests to group means with unequal numbers of replications. Biometrics. 1956;12(2):307-310.
13. Kucheriya N. Evaluation of rice distillers grains with solubles as alternative protein source in commercial chicken [PhD thesis]. Kolkata: WBUAFS; 2019.
14. Kumar SU, Sihag SZ, Sihag SA, Singh NA. Effect of substituting soybean meal with DDGS on nutrient metabolizability and carcass traits of broiler chicken. Haryana Vet. 2017;56(1):50-54.
15. Loar RE II, Moritz JS, Donaldson JR, Corzo A. Effects of feeding distillers dried grains with solubles to broilers from 0 to 28 days post hatch on broiler performance, feed manufacturing efficiency, and selected intestinal characteristics. Poult Sci. 2010;89(10):2242-2250.
16. Luu HM, Nguyen NX, Tran CB, Bui PT, Truong VP. Composition and nutritive value of rice distillers' byproduct (hem) for small-holder pig production. Livest Res Rural Dev. 2009;21(12):Art #212.
17. Raju MVLN, Rao SVR, Prakash B. Performance, serum biochemical profile, slaughter characteristics and nutrient retention of Vanaraja chicks fed rice-based distillers dried grains with solubles in diet. Indian J Anim Res. 2022;56(2):182-186.
18. Ranjan A, Samanta G, Samanta G. Rice-based distiller dried grains and solubles in duck egg production and its quality. Indian J Poult Sci. 2017;52(3):255-258.
19. Rochell SJ. Formulation of broiler chicken feeds using distillers dried grains with solubles. Fermentation. 2018;4(3):64.
20. Shirisha R, Vijaya Lakshmi K, Daida Krishna, Nalini Kumari N, Raju MVLN. Effect of rice distiller's dried grain soluble with or without enzyme supplementation on growth performance, immune organs and serum biochemical parameters of broilers. Indian J Poult Sci. 2021;56(2):107-114.
21. Singh N, Dubey M, Doneria R, Gendley MK, Dinani OP, Ramteke RC. Effect of feeding different levels of rice distillers dried grains with solubles (RDDGS) on performance of broilers. Indian J Anim Nutr. 2020;37(2):172-178.
22. Snedecor GW, Cochran WG. Statistical Methods. 7th ed. Ames (IA): Iowa State University Press; 1980.
23. Talsani KR, Kallam NRK, Narendra ND, Srinivas KD. Effect of incorporation of rice-based distiller's dried grain with soluble on growth performance and cost economics of Japanese quails. Indian J Poult Sci. 2021;56(2):135-139.
24. Thein SM, Thu TM, Thu KL, Thu WW, Thae C, Thet M, et al. Effects of dietary supplementation of rice distillers dried grains in grower phase on growth performance and digestibility of broiler chicken. Adv Anim Vet Sci. 2020;8(4):444-451.
25. Xue PC, Dong B, Zang JJ, Zhu ZP, Gong LM. Energy and standardized ileal amino acid digestibilities of Chinese distillers dried grains, produced from different regions and grains fed to growing pigs. Asian-Australas J Anim Sci. 2012;25(1):104-113.
26. Yang C, Tang X, Yang H, Tang Q, Tang J, Bin D. Effects of fermented wheat-rice distillers dried grains with solubles on meat quality and amino acid profile in broilers. S Afr J Anim Sci. 2019;49(5):957-965.