Effect of dietary inclusion of Rice Distillers Dried Grains Solubles (RDDGS) with or without enzyme on serum biochemical profile and carcass characteristtics in broilers

Introduction

Feed constitutes nearly 70% of total poultry production cost, making it a critical factor influencing profitability. The rising cost and inconsistent availability of conventional feed ingredients, particularly maize and soybean meal, along with competition with human food resources, necessitate the exploration of alternative feed ingredients. In this context, distiller dried grains solubles (DDGS), a by-product of the bio-ethanol industry, has emerged as a promising and economical feed resource. DDGS is a protein-rich ingredient composed of approximately 65% distillers grains and 35% solubles (AAFCO, 2005) [1] . The fermentation of starch during ethanol production results in concentration of nutrients, especially protein and phosphorus (Ruan et al., 2017) [21] . Despite its nutritional advantages, higher levels of non-starch polysaccharides (NSPs) in DDGS can limit nutrient digestibility and metabolizable energy availability (Pedersen et al., 2007) [18] . In India, the expansion of the ethanol blending programme has significantly increased DDGS availability, with production projected to rise from 3.2 million metric tons in 2024-25 to 4.2 million metric tons in 2025-26 (BioEnergy Times, 2025). Among various types, rice distiller dried grains solubles (RDDGS) has gained attention due to its substantial nutritional value, containing around 44-50% crude protein and appreciable energy levels (Gupta et al., 2015, However, its utilization in broiler diets is constrained by NSP content (Barekatain et al., 2013) [3] . Supplementation of exogenous enzymes such as protease has shown potential in improving nutrient digestibility and utilization in RDDGS-based diets (Dinani et al., 2022; Pont et al., 2023) [8, 19] . Although most studies have emphasized multi-enzyme combinations, limited information is available on the use of protease alone, particularly in high-protein rice DDGS. Therefore, the present study was undertaken to evaluate the effect of dietary inclusion of rice distillers dried grains solubles (RDDGS), with or without protease supplementation on serum biochemical profile and carcass characteristics in broiler.

Materials and Methods

Experimental birds and diets

The experimental protocol was approved by the Institutional Animal Ethics Committee (IAEC) under Ref. no: 281/go/ReBi/S/2000/CPCSEA/CVSc/TPTY/052/Animal Nutrition/2024 dated: 07.05.2024. Two hundred and forty (240), day old commercial broiler chicks were randomly (CRD) allocated to six treatment groups (T 1 , T 2 , T 3 , T 4 , T 5 and T 6 ), with four replicates of each containing 10 birds. The experiment was carried out from day-old to 42 days of age in three phases (pre-starter, starter and finisher). Isocaloric and isonitrogenous experimental diets were formulated for broiler pre-starter (0-7 days), starter (8-21 days) and finisher (22-42 days) phases as per the nutrient requirements of broilers (BIS, 2007) shown in Table 1, 2 and 3. The basal diet (maize and soybean meal) was control (T 1 ), while the other experimental diets consists of basal diet with protease enzyme (T 2 ), 12.5% RDDGS (T 3 ), 12.5% RDDGS with protease enzyme (T 4 ), 15% RDDGS (T 5 ), 15% RDDGS with protease enzyme (T 6 ). The enzyme protease was procured from Kemin Industries South Asia, Pvt. Ltd., Chennai marketed as KEMZYME® PROMACH 5; it was supplemented at a dose of 300 mg/kg.

Data collection

Blood samples were collected during slaughter from two birds per replicate and serum was separated by centrifugation at 3000 rpm for 10 minutes. The serum was stored at -20 °C until analysis. Serum biochemical parameters, including glucose, total protein, albumin, triglycerides, total cholesterol, creatinine, calcium, phosphorus and enzyme activities (ALT and AST), were analyzed using an A15 automated biochemical analyzer with Biosystem kits. At the end of the growth trial, two birds per replicate (eight birds per treatment) were randomly selected for carcass evaluation. Birds were fasted for 10 hours with free access to water prior to slaughter (Halal method). After bleeding, carcass weight was recorded and the head, shank and skin were removed. Evisceration was carried out to collect giblets (heart, liver and gizzard). Primal cuts and giblets were weighed and their percentages were calculated based on carcass weight. Dressing percentage was determined using eviscerated carcass weight relative to live body weight. Meat quality parameters like pH was measured using a digital pH meter after homogenizing meat samples with distilled water. Drip loss was estimated after 24 hours of storage at 4 °C, while water holding capacity (WHC) was determined by a centrifugation method using NaCl solution. Cooking loss was calculated from weight differences before and after cooking. Lipid oxidation (TBARS) and free fatty acid content were determined using standard procedures and proximate composition was analyzed as per AOAC (2019) [2] . Statistical analysis of the experimental data was performed using one-way ANOVA as described by Snedecor and Cochran (1994) [24] and differences among treatment means were assessed using Duncan's multiple range test (Duncan, 1955) [9] with SPSS Version 21.0 software.

Results and Discussion

The results pertaining to effect of feeding different levels of RDDGS with or without enzyme on serum biochemical profile are presented in Table 4. The serum biochemical profile of broilers fed diets containing 12.5 and 15% RDDGS with or without enzyme showed no significant differences in serum glucose, total protein, albumin, globulin, A/G ratio, creatinine, calcium, phosphorus and liver enzymes (ALT and AST) across treatments. These findings are in agreement with earlier reports by Kumar et al. (2022) [14] , Raju et al. (2022) [20] , Dinani et al. (2018) [7] , while Gacche et al. (2015) [10] reported that total serum protein, serum albumin, ALT and creatinine were similar in all the groups, however, AST level increased (p < 0.05) with increasing levels of DDGS in the diet. However, serum triglycerides and total cholesterol levels were significantly (p < 0.05) reduced in birds fed higher levels of RDDGS at varying levels 12.5 and 15% inclusion with or without enzyme supplementation. Similar reductions in lipid parameters have been reported by several authors ( [7,23,14] . The reduction in lipid profile may be attributed to the presence of unsaturated fatty acids and fermentation byproducts in RDDGS, which enhance lipid metabolism (Min et al., 2012 and Raju et al., 2022) [16,20] and reduce cholesterol synthesis (Crowell, 1999) [6] . Overall, inclusion of RDDGS up to 15% with or without enzyme supplementation did not negatively affect serum biochemical constituents, while improving lipid profile in broilers. The effect of feeding rice distillers dried grains solubles (RDDGS) with or without enzyme on carcass characteristics in broilers is presented in Table 5. The live weight (g) and carcass weight (g) were significantly (p < 0.01) higher in diet incorporated with 12.5% RDDGS with enzyme (T 4 ), while no significant differences were observed among the other treatments (T 1 , T 2 , T 3 , T 5 and T 6 ). The dressing percentage, weight of primal cuts (breast, thigh, drumstick and leg) did not show any significant (p > 0.05) difference among the treatments T 1 to T 6 . The present results align with Kim et al. (2016) [13] also observed that low-fat DDGS at 12% level improved carcass yield in broilers. Furthermore, the results agree with the findings of Kumar et al. (2017) [15] , who demonstrated that replacing soybean meal with DDGS up to 15%, with or without lysine supplementation, did not significantly affect carcass traits in broilers. The effect of feeding RDDGS with or without enzyme on the physical properties of meat is presented in Table 6. The results indicated no significant differences in pH, drip loss, water holding capacity, cooking loss, TBARS and free fatty acid content among the treatments. The present results are in agreement with the findings of Min et al. (2012) [16] , who reported that, there was no significant difference in pH, drip loss and free fatty acid content of breast muscle of birds. Similarly, Schilling et al. (2010) [22] reported no significant effect on cooking loss when broilers fed diets containing up to 24% RDDGS. However, TBARS values which is indicative of lipid oxidation, increased with higher levels of RDDGS inclusion (18% and 24%) as reported by Schilling et al. (2010) [22] . Incorporation of RDDGS at varying levels (12.5 and 15%) with or without enzyme showed no significant (p > 0.05) differences in proximate composition (DM, CP, EE and total ash %) broiler's meat among the treatments (Table 7). These findings are in agreement with Schilling et al. (2010) [22] who reported no significant effect of RDDGS inclusion on broiler meat composition. Similarly, Srikala (2017) [25] also reported no significant differences in the proximate composition of meat in quails fed diets with graded levels of RDDGS with or without spent brewer's yeast. 2.0 2.0 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.75 1.75 1.9 1.9 1.9 1.9 DCP 1. 25 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.

Conclusion

The feeding of RDDGS levels of 12.5% and 15%, respectively with or without enzyme supplementation do not have any adverse effects on the carcass traits, physical properties and proximate composition of broiler's meat, but inclusion of protease enzyme with RDDGS shown beneficial effect in reducing serum triglycerides and total cholesterol level.

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