Effects of Dietary Level of Rice Distiller’s Dried Grains on Performance and Meat Quality of Chickens

Distillers dried grain (DDG) is a co-product of ethanol production from cereal grains. DDG contains high protein, lipid, mineral, fiber content and other unfermented components of the grain and yeast cells (Oanh et al., 2019a; Salim et al., 2010). Hence, DDG has been of great interest to researchers in the area of animal science, especially to the animal feeding industry as the majority of this has been sold as feed ingredients for livestock (Dinani et al., 2018; Dipak et al., 2019; Oanh et al., 2019b; Raju et al., 2021).

In Vietnam, feed production is primarily depending on imported raw materials resulting in domestic livestock products more uncompetitive compared to imported animal products. Therefore, to reduce the production cost, the use of local feed resources and agro-industrial by-products is essential. Rice distillers dried grain (rice DDG) is a by-product of ethanol production from rice grains. Rice DDG contains 70.4% crude protein (approximately 3.6% lysine), 9.7% lipid, 2.9% crude fiber (Taranu et al., 2019). This by-product is considered as good source of protein for animal production. In previous study which showed that broiler chickens fed diets with inclusions of rice DDG at up to 12.5% had no differences in daily gain, feed intake, feed to gain ratio in comparison with control standard diet.

Previous studies have shown that the safe ratio of DDG in the diet is 5-8% (early stage for broilers and turkeys), 10-15% (in fattening-stage for broilers, turkey and layer hens), with these proportions being part of the cost of using soybean meal and corn or other expensive grains (Batal and Dale, 2003; Lumpkins et al., 2004). These authors also showed that laying hen diets containing 15% corn DDG would reduce egg productivity in layer hens because these by-products have a high proportion of crude fiber and non-starch polysaccharides. Around the world, DDG by-products of alcohol processing from corn and wheat have been widely used in livestock production in the past 15 years. However, by-products from rice-based ethanol processing are little researched and used as animal feed. Therefore, this study aimed to evaluate the effect of dietary level of rice DDG on performance, meat yield and quality of broiler.

Animals, experimental design and diets
 
The experiment was carried out on Ri - DABACO colored broilers from birth to 14 weeks of age at the experimental station of Faculty of Animal Science, Vietnam National University of Agriculture, Vietnam from May to September 2020.

A total of 240 birds were arranged into 4 dietary treatments, including a basal diet (control, DDG0) and 3 experimental diets containing 5% (DDG5), 8% (DDG8) and 10% (DDG10) of rice DDG according to a completely randomly design, with three replications. Each replication comprises 20 birds (10 males and 10 females). All animals were individually numbered, housed in pens and given feed, clean and fresh water ad libitum.

Wet distiller grain samples from a rice-based beverage ethanol distillery located in Phu Tho province (North Vietnam) was collected immediately after production. These samples were then dried at 90°C for 30 min, 80°C for 2.5-3.0 h and 70°C for 1.0 h respectively. After that, rice DDG was packed in a plastic bag and stored at room temperature for further chemical analysis.

The basal diet (DDG0) was formulated to meet the nutrient requirements of broilers according to NRC (1994). The other experimental diets were established by the partial replacement of soybean meal in the basal diets to different levels of rice DDG. After the individual feed was made, a representative sample was taken from each dietary treatment for the determination of chemical compositions. The ingredients and chemical composition of the diets are presented in Table 1. Rice DDG and diets were analyzed for moisture, crude protein, fat, ash, calcium, phosphorous, crude fiber (AOAC, 1990), starch was determined by the method as previously described (Le et al., 2006). For amino acids analysis, the HPLC analysis of the Agilent 1200 series (Germany) with a DAD detector was performed.


 
Measurements
 
Chickens were individually weighed every week from the initial day to the final day of the experiment for calculation of the body weight and average daily gain (ADG). Average daily feed intake (ADFI) was determined daily per pen by measuring feed residues. The feed conversion ratio (FCR) was calculated by dividing feed intake by body weight gain.

At the end of the experiment, for each treatment, six chickens (3 males and 3 females) with weight around the average weights of birds were used to evaluate carcass characteristics such as carcass, heart, liver, thigh and breast weight.
 
Muscle pH
 
At 15 min and 24 h post-mortem, the breast and leg muscle pH was respectively determined at a depth of 2.5 cm below the surface by using Testo 230 (Germany).
 
Color measurement
 
Surface color of chicken rolls was measured in package using a Minolta CR-410 (Japan) colorimeter and expressed as color L*(lightness), a*(redness) and b*(yellowness) values as previously described (Oanh et al., 2019a).
 
Tenderness
 
Tenderness of thigh and breast muscle 24 h post-mortem was evaluated by using Warner - Bratzler 2000D machine (USA).
 
 
Statistical analysis
 
The effect of different levels of rice DDG in the diets on performance and meat yield and quality of broilers were determined by one-factor variance analysis using SAS 9.1 (2002). The statistical model was:
 

Y_ij = µ + F_i + e_ij

 
Where
Y_ij is the observed values, µ is the average normalized record, F_i is the effect of different levels of rice DDG in the diets (i = 4: 0, 5, 8, 10), eij is the residual error. Treatment means were compared by Duncan’s new multiple range test.

Nutritional values of rice DDG
 
The result of chemical compositions and nutritional values of rice DDG analysis show that rice DDG has relatively high contents of crude protein (70.4%), digestible energy (DE, 5791 kcal/kg) and ME (4592 kcal/kg). The amino acid content in rice DDG is also quite high with 3.6% lysine, 2.6% tryptophan and 2.1% threonine. However, crude fiber content (2.9%) was low in rice DDG (Table 2). The nutritional value of rice DDG was mentioned in a previous studies (Dinani et al., 2018; Oanh et al., 2019b; Taranu et al., 2019). Being compared to other DDG sources, rice DDG contained more protein, thus higher in amino acid content. Several authors reported that the protein content in corn DDGS was ranged from 26 to 32% (Belyea et al., 2010; Spiehs et al., 2002) with lysine, methionine and threonine were 0.89, 0.53 and 1.14% respectively. Similarly, the wheat DDG contained 38.48% crude protein, 0.97% lysine, 0.36% tryptophan and 1.09% threonine (Cozannet et al., 2009). Thus, with high protein, amino acid and low fiber content, rice DDG can be a potential source of raw materials to replace protein-rich feeds for poultry.

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Effect of rice DDG on production parameters
 
There were no significant differences among treatments in body weight of broilers at 4 and 8 weeks of age (Table 3). However, at 12 and 14 weeks of age, chickens fed with diets containing different levels of rice DDG were higher in body weight than chickens fed the control diet (P<0.05). From 4 to 8 and from 8 to 12 weeks of age, the ADG was not significantly different (P<0.05) by levels of rice DDG in the diet. However, in the period of 12-14 and 4-14 weeks of age, ADG was a significant difference among treatments (P<0.05) with the greatest values for the diet containing 10% rice DDG and followed by 8 and 5% rice DDG in the diets. The level of rice DDG in the diet did not significantly affect ADFI and FCR. In some previous studies have shown that distillers dried grains with solubles (DDGS) did not affect ADG, ADFI and FCR of broiler chickens (Sariozkan et al., 2015; Thein et al., 2020; Wang et al., 2007). Some others indicated that the use of DDGS in the diets improved the growth performance (Kaya and Sahin, 2013; Shim et al., 2011). Dinani et al. (2018) found that broiler diet containing 15% rice DGS reduced ADG, ADFI and FCR. The different above results may be due to the different grain DDGS sources, nutritional values of DDGS sources and the different levels of DGS used in the diets, as well as different broiler breeds. In this study, the usage of rice DDG up to 10% in the diets resulted in a positive effect on body weight and ADG at 12 and 14 weeks of age.

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Effect on meat yield and quality
 
Different levels of rice DDG used in the diets did not significantly affect meat yield and quality (Table 4). The results of this study are consistent with some previous studies (Dinani et al., 2018; Raju et al., 2021) which also found that the use of rice DGS in chicken diets did not affect carcass traits. Similarly, the diets containing 10-15% DDGS had similar carcass yield to the control (Sariozkan et al., 2015; Wang et al., 2007). Moreover, Youssef et al. (2013) found that using 10-15% DDGS as a protein source in broiler diets did not have any significant effect on the weight of organs such as the heart, liver and gizzard. On the other hand, broiler chickens fed diets containing inclusion of rice DDG levels also had no significant effect on meat color parameters (L*, a* and b*), which are consistent with earlier works (Choi et al., 2008; Schilling et al., 2010).

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Inclusion of 5, 8 and 10% rice DDG in the diet for broilers did not affect body weight, average daily gain in the early experimental period (4-8 weeks of age) but had a positive effect on these parameters in the post-experimental period (12-14 weeks of age). Feed intake, feed conversion ratio, meat yield and quality were not significantly affected by the dietary inclusion level of rice DDG. It could be suggested that rice DDG can be a potential source of raw materials to replace protein-rich feeds for poultry.

The authors acknowledge financial support from the Ministry of Science and Technology (Vietnam) and the Ministry of Education and Scientific Research (Romania) via the bilateral project (Grant No. 15/2014/HD-NDT).