Effect of feeding rice distillers dried grain with solubles as major protein source on nutrient digestibility and growth performance of Jersey crossbred calves

India is the leading producer of milk but productivity of our animals is much lower than the global average, due to inadequate and unbalanced feeding. Feed cost accounts up to 60 percent of total expenditure of a farm. At present, the country faces a net deficit of 35.6% green fodder, 10.95% dry crop residues and 44% concentrate feed ingredients (IGFRI, 2013). The high cost and less supply of conventional animal feed ingredients in most of the developing countries has increased the demand for alternative ingredients. This situation has given an impetus to search newer and alternative feed resources to bridge the gap between demand and supply. Use of unconventional feed resources in place of conventional feed can reduce the cost of production. For production of biofuel, different types of cereals are in use and millions of tons of fermentation residues are available to the feed industry for its use as animal feed. Rice Distillers Dried Grains with Solubles (RDDGS) is a byproduct of the processing of alcohol industry which is produced from the distillation of fermented rice. In processing of rice alcohol, rice is cooked at 131°C and 2.6 kg/ m² pressure and yeast is added to the cooked rice for fermentation (Huang et al., 1999). From fermentation liquor the alcohol is distilled and then leftover is known as RDDGS. It contains 47% protein (NRC, 1989) and around 3500 kcal/ kg metabolisable energy. Since it is recovered from fermented grains it is more nutritious than the cereal grains from which it is made up of. It does not contain any antinutritional factor, as might be the case with trypsin inhibitors in soybean. Distillers grains with solubles have been reported to be a good source of rumen undegradable protein (RUP) and energy for ruminants and may be included up to approximately one third of the diet for lactating dairy cows (Schingoethe et al., 2009). The positive effect of feeding DDGS have been reported by some earlier workers on growth (Benson et al., 2005; Engel et al., 2014) and feed conversion efficiency (He et al., 2015; Vander Pol et al., 2009). Scientific studies regarding the effect of inclusion of RDDGS in ration replacing Soybean Meal (SBM) on growing Jersey crossbred calves is limited. Therefore, the present investigation was carried out to study the effect of feeding RDDGS on digestibility of nutrients, growth performance and feed conversion efficiency of crossbred Jersey calves.

Selection, care and feeding of animals
 
From the herd of ERS, NDRI, Kalyani twelve growing Jersey crossbred calves were selected, randomly divided into Control (T₀)  and Treatment (T₁) groups of six animals each having similar average age (7.5 months) and body weight (113.1±12.1 and 113.9±13.1 kg in T₀ and T₁, respectively). Experimental animals were dewormed and vaccinated as per farm schedule. Animals in T₀ and T₁ groups were fed individually with paddy straw, green fodder and concentrate mixture as per ICAR (2013) requirements for 120 days. Two types of iso-nitrogenous concentrate mixtures were preparedand their ingredient composition is presented in Table 1. Clean and fresh drinking water was offered adlibitum twice to each animal daily at 10.00 and 16.00 h.
 

 
Record of intake and body weight
 
Dry Matter Intake (DMI) was recorded daily for individual animal. Animals were weighed at the start of experiment and then at fortnightly interval for two consecutive days before feeding and watering. The average of two days was considered as the body weight for that fortnight.
 
Sample collection and chemical analysis
 
Samples of RDDGS, feeds and fodders offered andresidue left were collected, pooled and processed weekly for further analysis. The samples were analyzed for different nutritional parameters as per AOAC (2005). Cell wall fractions in samples were analysed according to Van Soest et al. (1991). Blood samples were collected in heparinized tubes (10 ml) from Jugular vein before offering feed in morning at 0, 60^th and 120^th days of growth trial. The collected blood samples were centrifuged (3000 × g for 30 min at 4°C) and the plasma samples were frozen immediately at -20°C for further analysis. Plasma glucose, total protein, albumin, globulin, blood urea, ALT and AST levels were estimated using analytical kits (Span Arkray Healthcare Pvt. Ltd. India) as per standard procedure.
 
Estimation of digestibility of nutrients
 
After 75 days of experimental feeding a six days digestion trial was conducted to determine the nutrients digestibility. Well-mixed representative samples of concentrate, paddy straw and green fodder were collected. In the morning, the record of residue left and feaces voided by each animal was taken and representative samples were collected for further analysis. The collected samples were analysed for DM, OM, CP and EE as per AOAC (2005). NDF and ADF were analysed according to Van Soest et al. (1991). Nutrient digestibility was estimated by using difference method.
 
Statistical analysis
 
The data obtained during the growth study were subjected to statistical analysis in accordance with Snedecor and Cochran (1968) using SPSS software.

Chemical composition of RDDGS
 
The chemical composition of RDDGS and SBM has been presented in Table 2. The DM content of RDDGS was 89.58±0.09%. The proximate composition (% DM) in terms of OM, CP, EE, NFE and total ash were 94.97±0.09, 48.43± 0.69, 5.45 ± 0.16, 34.58±1.15 and 5.03 ± 0.09, respectively. The cell wall constituents (% DM) in RDDGS in terms of NDF, ADF, TCHO and AIA were 40.50±0.9, 16.82±0.65, 42.91±1.5 and 0.95±0.06, respectively. Liu (2011) also reported similar nutrient values for RDDGS. Crude protein content of RDDGS was similar to SBM (48.43 and 48.50%, respectively) but EE, NDF and ADF content were comparatively higher in RDDGS than SBM.
 

 
Chemical composition of feeds and fodder
 
The chemical composition of straw, green fodder and concentrate mixtures have been presented in Table 3. The average CP content of paddy straw and green fodder were 3.25 and 14.34 percent of DM, respectively. There was not much difference in chemical composition of the two concentrate mixtures. The CP content of control and treatment concentrate mixtures were 24.24 and 24.04 percent of DM, respectively indicating the two diets offered to control and treatment groups were isonitrogenous. The EE content was slightly higher in treatment concentrate mixture due to higher EE content in RDDGS than SBM.
 

 
Effect of RDDGS feeding on nutrient digestibility
 
The digestibility coefficients of various nutrients have been presented in Table 4. Inclusion of RDDGS in place of SBM in concentrate mixture improved the digestibility of DM and CP significantly (P<0.05) in T₁. The reason for higher digestibility of CP could be the bypass protein and residual yeast single cell protein content of the RDDGS (Castillo-Lopez et al., 2010). Ojowi et al., (1996) reported that wet distillers grains have lower rumen undegradable crude protein values than dried distillers' grains. Schingoethe et al., (2009), suggested that the RUP contained in DDGS is 55% when fed to dairy cows. Paz et al., (2013) determined the average RUP digestibility to be 83.9 %.
 

       
The digestibility coefficient for the EE was also significantly higher in T₁ (P<0.01) than T₀ group. Due to higher EE content in treatment concentrate mixture the EE intake was comparatively higher in the treatment group. The source of this increased EE in the treatment diet is RDDGS, which is having very good fatty acid profile. The incorporation of RDDGS replacing SBM in treatment diet positively influenced the ether extract supply both quantitatively and qualitatively. These may be the possible reasons for significant increase in EE digestibility. Vander Pol et al., (2009) found higher proportions of elaidic, oleic and linoleic reaching the duodenum in WDGS fed cattle when compared to corn fed. Corrigan et al., (2009) observed a 3.4% increase for fat digestibility for diets containing 40% WDGS.
       
Statistical analysis of the data showed that ADF, NDF and total carbohydrate (TCHO) digestibility was similar in T₁ and T₀ groups. Castillo-Lopez et al., (2010) fed diets with increasing increments of reduced fat DDGS from 0 to 30 % to lactating dairy cows and reported no difference in DM or NDF digestibilities. Diets containing DDGS were not different for total-tract starch digestibility compared to diets containing no DDGS (Corrigan et al., 2009).
 
Effect of feeding RDDGS on intake parameters of Jersey crossbred calves during digestibility trial
 
The data on DM, CP and TDN intakeduring digestibility trial have been presented in Table 5. The average DMI as percent of bodyweight were 2.51±0.04 and 2.77±0.09 in T₀ and T₁ groups, respectively. The roughage: concentrate ratio in T₀ and T₁ groups were 38.2:61.8 and 41.6:58.4, respectively indicating slightly higher proportion of concentrate intake in control group. There was no significant difference (P>0.05) in DM, CP, DCP and TDN intake between two groups indicating replacement of SBM by RDDGS in treatment diet has no adverse effect on intake parameters. Higher DCP and TDN intake, though statistically non-significant, in treatment group as compared to control group may be attributed to significantly higher DM, CP and EE digestibilityin treatment group as compared to control group.
 

 
Effect of RDDGS feeding in concentrate mixture on blood biochemical profile
 
The data on blood parameters have been presented in Table 6. The plasma glucose, total protein, albumin, globu lin, AST and ALT concentration did not vary significantly and were within normal range  between the control and treatment groups, indicated that there was no adverse effect of feeding RDDGS replacing SBM.
 

 
Effect of RDDGS feeding on intake and growth performance of Jersey crossbred calves
 
The average intake of nutrients, average daily gain (ADG), feed conversion efficiency (FCE) and Feed conversion ratio (FCR) have been presented in Table 7. The average DMI (kg/d/100kg body weight) were 2.49±0.04 and 2.51±0.08 in T₀ and T₁ groups, respectively without any significant difference. Similarly there was no significant (P>0.05) difference in CP intake (g/kg W0.75) between two groups. The TDN intake (g/kg W^0.75) was higher (though statistically nonsignificant) in T₁ (60.07±1.71) as compared to T₀ (55.19±1.68) which may be due to higher digestibility of some nutrients as obtained for treatment group (Table 3). The results were in accordance with Sihag et al., (2018) who replaced GNC in control group with DDGS at three different levels and reported no differences among treatments for DMI in crossbred dairy cattle.
 

       
The ADLG (g/d) was significantly (P<0.01) higher in T₁ (688.9 ± 29.7) than T₀ (550.7 ± 16.7). Engel et al., (2014) also found similar result in heifers. The improved digestibility of EE, CP and DM as a result of RDDGS incorporation, might have resulted in significant improvement in growth performance. Similar to the current findings,Benson et al., (2005) evaluated the effects of replacing 15, 25, or 35 percent cracked corn with DDGS  in steers and reported greater ADG at 25 percent DDGS in diet. The also improved by around 17 percent in T₁, though the difference between two groups were statistically non significant. Inclusion of DDGS in Holstein calf diet increased papillae length and width (Jun et al., 2014) and improved FCR (He et al., 2015). Vander Pol et al., (2009) showed that including WDGS in the diet increased FCE when compared to corn.
       
In the present experiment the only difference between the two groups was that the SBM in the control concentrate mixture (25%) was totally replaced by RDDGS in the treatment concentrate mixture. Thereby, any significant change in intake, digestibility and growth parameters should be considered as the impact of incorporation of RDDGSreplacing SBM. The digestibility of EE, CP and DM improved significantly as a result of incorporation of RDDGS, which might have resulted in significant improvement in growth performance. There are reports on reduction in methane production with inclusion of DDGS in dairy and beef cattle (Benchaar et al., 2013; Hunerberg et al., 2013), which may be due to increased fat in diet inhibiting growth of the protozoa population (Knapp et al., 2014). In the present study also inclusion of RDDGS replacing SBM have increased the fat percent of the diet. This suggests that at least a portion of energy retained from reduced methane loss was utilized for growth. Castillo-Lopez et al., (2010) determined that the concentration of yeast protein contained in DDGS was 1.4% (DM-basis). Ingledew (1999) suggested that 3.9% of the dry weight of DDGS may be contributed by yeast cell biomass and that the greater value of distillers byproducts (average daily gain, feed efficiency) may be at least partially explained by the contribution of yeast components that influence ruminal fermentation.
       
The improvement of production performance may be the resultant of several factors such as better chemical profile of RDDGS, improvement of nutrient digestibility, reduction of methane production due to increased fat in diet, presence of yeast cells and some other hidden factors. Keeping in view, lower price of RDDGS, it can economically replace SBM fully in concentrate mixture of ruminants without any adverse effect and thus enhance the net profit. However, long term feeding trial in cattle or other ruminants is recommended to ascertain the effects of feeding such distillery by-product on productive performance and health. 

Financial and Material support from the Director, ICAR-NDRI, Karnal and IFB Agro Industries Limited, Kolkata for carrying out the study are thankfully acknowledged.