CC BY
22019, Scienceline Publication
World's Veterinary Journal
World Vet J, 9(3): 192-200, September 25, 2019
https://dx.doi.org/10.36380/scil.2019.wv25
Use of Untreated and Autoclave-Treated Wheat Germ Meal in Growing Rabbit Diets
Walaa Attia Salama*, Amira Mahmoud Refaie, Hamdy Farouk Amin and Lamiaa Fathy Abdel-Mawla
Animal Production Research Institute, Agricultural Research Center, Giza, Egypt.
•Corresponding author's Email: dr.walaa..attia@gmail.com; ORCID: 0000-0002-1854-1986
ABSTRACT
The present study was intended to investigate the influence of using 20% and 40% treated or untreated wheat germ meal in growing New Zealand rabbit diets. A total of 75 weaned New Zealand White rabbits aged six weeks old, with an average initial weight of 659.60±18.84g were divided into five groups with five replicates in each group (three rabbits per replicate). The first group was fed on a basal diet (Ti), second and third groups received diets containing Wheat Germ Meal (WGM), as replacement of soybean meal protein, at levels of 20% and 40% and were labeled as T2, T3, respectively. Fourth and fifth groups were fed with 20% and 40% autoclave-treated WGM (T4 and T5, respectively). The trial was continued until 14 weeks of age. The present study was evaluated growth performance, blood parameters, carcass traits, meat quality in different groups and also economic efficiency was calculated. There were insignificant differences in terms of live weight, daily weight gain, carcass weight and dressing percentages among rabbits in groups of T1, T2, and T Rabbits in the group of T4 achieved the best feed conversion ratio. Digestion coefficients of crude protein, crude fiber, ether extract, nitrogen-free extract, and nutritive value in terms of digestible crude protein, total digestible nutrition, and digestible energy did not significantly differ between T1 and T4. However, these factors significantly decreased in T3 and T5 compared to T1. Plasma total protein and globulin significantly increased in rabbits of T2 and T4 compared to those fed in T1 group. A significant decrease in total cholesterol and total lipid for rabbits in groups of T4, T5, and T2 was observed. Moreover, rabbits fed on T4 or T2 diets had the highest economic efficiency. Conclusively, the untreated or autoclaved WGM can be used in growing rabbit diets up to 20% for replacing the soybean meal protein, which caused low feed costs without adverse effects on the growth performance of rabbits.
Key words: Rabbits, Soybean meal, Wheat germ meal INTRODUCTION
Wheat, maize, rice, oats, barley, millets, sorghum, and rye are important cereals for human nutrition, either for cooking or as raw material for obtaining flour for baking (De Vasconcelos et al., 2013). Wheat is one of the important cereals and food ingredients around the world due to its ability to be converted to flour. Wheat flour is produced by milling wheat and extraction rate varies from 73% to 77%, depending on the variety of wheat and the production conditions (Elliott et al., 2002). Therefore, in the milling process, by-products such as wheat germ, wheat bran and parts of the endosperm comprise 23 to 27% of the production.
The wheat germ as a significant by-product of the cereal industry accounts for 2.5 to 3.8% of the total grain weight (Brandolini and Hidalgo, 2012). The wheat germ oil is the richest natural source of vitamin E (a-tocopherol) (Gerald et al., 2017). Hafez et al. (2019) found that rats received 3g/kg wheat germ oil had a non-significant increase in Malondialdehyde (MDA) levels of serum at the 15th day of study as compared to control group. Saleh (2016) found that oral administration of wheat germ oil (1400 mgkg) to mice for eight days improved the liver and small intestine damage induced by carbon tetrachloride.
The Wheat Germ Meal (WGM) is produced when the oil is extracted from the wheat germ. WGM is high in protein content and rich in carbohydrates which could be processed further into livestock feeds. WGM as a good source of water-soluble vitamins also has a high content of lysine, threonine, and histidine (Barton and Monr, 1946). In addition, Moran and Summers (1967) reported that WGM contains 29% Crude Protein (CP), 2.1% Crude Fiber (CF), 10.3% Ether Extract (EE). Moreover, it contains gluten and antinutritional factors such as hemagglutinins and trypsin inhibitor, which inhibit enzymatic digestion of proteins (Creek and Vasaitis, 1962). Therefore, methods such as autoclaving or biological treatment are essential for improving the nutritive value of WGM. Autoclaving destroys the activity of these factors (Creek et al., 1962). Moran and Summers (1967) demonstrated the Autoclaved Wheat Germ Meal (AWGM) at 121 °C for 20 minutes, incorporated to chicken diets at the level of either 47% or 63.8% improve growth performance and feed utilization compared to groups fed WGM autoclaved for 90 min and control group. Hence, the objective of the present
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study was to investigate the effects of partial replacement of soybean meal protein with autoclave treated WGM protein on feed cost and growth performance of rabbits.
MATERIALS AND METHODS
The experiments were conducted at Borg-El Arab, located in Alexandria governorate, Egypt. The autoclave treatments were performed at the laboratories of By-Products Research Department, Animal Production Research Institute, Agriculture Research Center, Giza, Egypt.
Ethical approval
The study was carried out after obtaining the ethical approval from the Animal Production Research Institute, Egypt.
Wheat germ meal processing
WGM was obtained from the processing and extraction unit of natural oils, National Research Center, Giza, Egypt. It was ground by a hammer mill and stored in an air-tight condition then kept for further processing.
Autoclave treatment
WGM was treated with an autoclave at 121 °C for 20 minutes as recommended by Moran and Summers (1967). After treatment of the WGM, the drying was done in the air for 10 min and then kept for chemical analysis before mixing to the diets. Dry gluten content was determined according to Haraszi et al. (2011) and trypsin inhibitor activity was assessed as defined by Makkar et al. (2008). These measurements were performed before and after treatment.
Animal management and feeding
Seventy-five weaned New Zealand White rabbits of both sexes (six weeks old, the average body weight of 659.60±18.84 g) were allocated to five dietary treatments of 15 rabbits per treatment. Each treatment was replicated 5 times (three rabbits per replicate). The T was fed the control diet, the T2 and T3 received 20% and 40% untreated WGM in replacing of soybean meal protein, respectively (6.12 and 12.31% of the whole diet, respectively). The T4 and T5 were fed on 20% and 40% autoclave-treated WGM, which consisted of 6.20 and 12.41% the whole diet, respectively. The ingredients and chemical composition of diets are presented in table 1. All the experimental diets were formulated to be isonitrogenous and isocaloric, to meet all the essential nutrient requirements of growing rabbits according to (Egyptian Agriculture Ministry Decree, 1996). The animals were reared in metal battery cages equipped with separated feeders and automatic nipple drinkers. All animals were receiving control diet for one week before the start of the experimental period and vaccinated against diseases during the veterinary examinations. Feed and water were offered ad libitum. The management and hygienic conditions were identical for all groups.
Table 1. Ingredients and chemical composition of experimental diets
Ingredients (%) T1 T2 T3 T4 T5
Barley 30.26 27.48 25.93 27.48 25.83
Clover hay 26.74 27.05 26.05 27.05 26.05
Wheat bran 18.40 18.40 18.40 18.40 18.40
Soybean meal (44% ) 18.10 14.47 10.86 14.47 10.86
Wheat germ meal -- 6.15 12.31 6.20 12.41
Molasses 3.00 3.00 3.00 3.00 3.00
Di calcium phosphate 2.20 2.20 2.25 2.20 2.25
Sodium chloride (NaCl) 0.30 0.30 0.30 0.30 0.30
Vit.& min. mix1 0.30 0.30 0.30 0.30 0.30
Lime stone 0.35 0.35 0.35 0.35 0.35
DL-Methionine 0.30 0.25 0.20 0.25 0.20
Anticoccidia (Diclazuril) 0.05 0.05 0.05 0.05 0.05
Total 100 100 100 100 100
Chemical analysis2
Crude protein (%) 17.70 17.37 17.04 17.36 17.06
Crude fiber (%) 12.87 12.64 12.08 12.65 12.08
Ether extract (%) 2.17 2.44 2.70 2.39 2.70
Nitrogen-free extract (%) 59.22 59.88 58.98 58.39 59.16
Digestible Energy (kcal/kg) 2533.35 2515.5 2512.5 2515.6 2512.4
Methionine+ cysteine (%) 0.55 0.54 0.54 0.54 0.54
Lysine (%) 0.91 1.10 1.28 1.09 1.28
T1: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave -treated wheat germ meal, T5: 40% autoclave-treated wheat germ meal. 1Vitamins (Vit.) and minerals mixture; each 3 kg contains: Vit. A 6000.000 IU, Vit.B1 2000mg, Vit.B2 4000mg, Vit.D3 900000 IU, Vit E 40000mg, Vit. K3 2000 mg, Pantothenic acid 10000mg; Nicotinic acid, 50000g; Vit. B6 2000 mg; Vit. B12 10 mg, Folic acid 3.0g, Biotin 50 mg, choline 250000mg, Cu 5g, Mn85g 60g, Fe 50g, , Co 0.1 g, Se 0.1 g, Zn 50 g, I 0.2 g and Antioxidant 10000mg. 2Chemical analysis of ingredients according to AOAC, 2000.
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Experimental parameters
Growth performance
Feed Intake (FI, g/ rabbit/ day) and Body Weight Gain (BWG, g/ rabbit/ day) were recorded weekly. Moreover, the Feed Conversion Ratio (FCR) was calculated as FI/BWG over an experimental period of 8 weeks.
Digestion trial
Digestibility test was carried out using five male rabbits from each experimental group in the last week of the experiment (14 weeks of age). The feces were daily collected separately for six days. The feces were sprayed with 2% boric acid solution for trapping released ammonia and dried at 60o C for 48 hours (until constant weight). Feces were ground and stored for subsequent chemical analysis. Samples of WGM, diets, and feces were analyzed for moisture, ash, Nitrogen-Free Extract (NFE), EE, CF, and CP according to AOAC (2000).
Carcass traits
At 14 weeks of age, 25 rabbits (five rabbits per treatment) were slaughter to determine carcass traits according to Biasco and Ouhayoun (1996).
Chemical meat measurement
Longissimus dorsi muscles from 25 samples were frozen at -20 °C for determination of total cholesterol, MDA and Total Antioxidant Capacity (TAOC) by colorimetric methods using analytical kits (Bio Diagnostic Company, Egypt)
Blood parameters
Blood samples were taken from the five rabbits per treatment at the time of slaughter and were collected in dry clean tubes containing heparin and centrifuged at 3000 rpm for 20 minutes. Then plasma was separated and stored in a deep freezer at approximately -20°C till the time for determining total lipids, total cholesterol, total protein, and albumin. Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) were colorimetrically determined using commercial kits, according to the manufacturer's instruction (purchased from Bio Diagnostic, Cairo, Egypt). The concentration of globulin (g/dl) was calculated by subtracting albumin from total protein values.
Statistical analysis
The experimental data were subjected to using analysis of variance (ANOVA) in the general linear model using SAS version 9 (SAS Institute Inc.) by the following model:
Yj= ^+Ti+ eij
Where ^ was overall mean of Yij; T was the effect of treatment; i was (1, 2..., etc.), and eij was experimental error. The Significant differences between treatments means were separated by Duncan's multiple range test (1955).
Economic efficiency
Economic efficiency was calculated using the following equation: Economic efficiency = Net revenue / total costs
Total cost was calculated in Egyptian pound according to the price at the time of the experiment.
RESULTS
Chemical composition
Chemical analysis of WGM and AWGM in comparison to soybean meal are shown in table 2. The CP was higher in soybean meal (44 %) compared to WGM (25.83%) and AWGM (25.62%). Also, the CF was higher in soybean meal (7.3 %) compared to WGM (1.28 %) and AWGM (1.22%). However, the EE of soybean meal was lower (1.50%) in comparison to WGM (6.02%) and AWGM (5.30%). On the other hand, DE of soybean meal was 3200 kcal/ kg closed with WGM (2900 kcal/kg) and AWGM (2901 kcal/ kg). WGM contained 4% dry gluten and trypsin inhibitor activity was 2.817 mg/g, while autoclave treatment reduced dry gluten by 50% and trypsin inhibitor activity by 62.4% compared to WGM.
Growth performance
The results of final body weight, daily BWG, FI, and FCR are presented in table 3. Rabbits fed either Ti or T4 showed significantly higher final body weight followed by group fed T2 compared to T3 and T5. While groups fed T3 and T5 had the lowest values. Rabbits fed control diet and T4 recorded insignificantly higher BWG compared to T2 and T5. While the lowest values were recorded for T3. The FI was not significantly affected by any of the tested diets. Regarding FCR, the group fed T4 recorded the higher value without significant differences with T1 group. Whereas, the lowest values were found in groups fed T3 and T5.
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Table 2. Chemical analysis of soybean meal, wheat germ meal and autoclave-treated wheat germ meal based on dry matter percentage_
Items Soybean meal* WGM AWGM
Organic matter (%) 93.50 93.40 93.48
Crude protein (%) 44.00 25.83 25.62
Crude fiber (%) 7.30 1.28 1.22
Ether extract (%) 1.50 6.02 5.30
Nitrogen-free extract (%) 40.7 60.27 61.34
Ash (%) 6.50 6.60 6.52
Digestible energy** (Kcal/kg) 3200 2900 2901
Anti-nutritional factors
Dry gluten (%) - 4.00 2.00
Trypsin inhibitor activity (mg/g) 21.00 2.817 1.058
WGM: Wheat Germ Meal, AWGM: Autoclave-treated Wheat Germ Meal. "Chemical analysis according to Feed composition for animal and poultry feedstuff used in Egypt (2001). ""Digestible energy calculation was performed according to (Cheeke, 1987).
Table 3. Growth performance of New Zealand White rabbits (six weeks old) fed diets containing untreated or treated wheat germ meal_
Items Ti T2 T3 T4 T5 SEM
Initial body weight (g) 645.00 668.00 671.00 641.00 673.00 18.84
Final body weight (g) 2143.3a 2031.7ab 1872.0c 2108.0a 1965.0bc 30.56
Daily body weight gain (g) 26.76a 24.35ab 21.44b 26.20a 23.07ab 0.70
Daily feed intake (g) 103.59 94.59 94.27 99.33 95.00 3.80
Feed conversion ratio (g feed/ g gain) 3.87bc 3.88bc 4.39a 3.79c 4.11ab 0.10
Different superscript letters within the same row mean significant differences (P<0.05). T1: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave-treated wheat germ meal, T5: 40% autoclave-treated wheat germ meal. SEM: Standard error of the mean.
Digestion coefficient
According to results shown in table 4, AWGM increased nutritive values for the rabbit compared with 40% untreated WGM. These results indicated that CP digestibility was significantly higher in T1 and T4 groups in comparison to other groups. Digestibility of CF, EE, and NFE were significantly improved in T1, T2, and T4. Digestible CP values were significantly increased in T1 and the lowest values were found with inculcation untreated or treated WGM at the level of 40%. Feeding with T4 and T1 diets enhanced total digestible nutrients, digestible crude protein and digestible energy compared to other treatments.
Carcass characteristics
The results of carcass characteristics are presented in table 5. Carcass and dressing percentage were significantly higher in T1, T2 and T4 in comparison to other groups. While T3 and T5 were significantly decreased in the carcass weight and dressing percentage compared to T1. However, the percentage of liver, kidney, heart, and giblets were not significantly affected by any treatments.
Meat quality
Table 6 shows that the T1 and T5 recorded the highest TAOC value values in rabbit meat followed by T2 and the lowest values were recorded for T3 and T4. The highest MDA value was recorded for T2 followed by T5 .While T1 group was found to have the lowest value. Regarding total cholesterol in rabbit meat, T2 recorded significantly the highest level. The lowest level was found in the groups of T5 and T3.
Blood constituents
The plasma concentration of total protein, albumin, globulin, total cholesterol, and lipids are shown in table 7. The obtained values of blood parameters were within the normal range. Insignificant differences were found in the concentration of plasma albumin, ALT and AST in different tested treatments. Plasma total protein increased significantly in T2 and T4 compared to control and T5 groups. Globulin values were significantly higher in rabbits fed T2 and T4 compared to other groups. The concentration of total cholesterol and lipid in plasma were significantly higher in T1 and T3 compared to control group.
Economic efficiency
Effects of replacement of treated or untreated WGM on economic efficiency are shown in table 8. The results indicated that inclusion 20 or 40% treated or untreated WGM decreased total feed cost /rabbit as a result of decreasing FI compared to control group. Growing rabbits fed diets either T4 or T2 recorded high economic efficiency followed by T1. Also, selling price increased in T4 than control (71.88 and 73.40 LE, respectively). The same trend was found in relative economic, where the best values were recorded in T4 and T2 groups (109.19 and 105.6 %, respectively), while the poorest value was recorded in T3 group.
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Table 4. Digestion coefficient of New Zealand White rabbits (six weeks old) fed on autoclave-treated or untreated wheat germ meal._
Items Ti T2 T3 T4 T5 SEM
Organic matter (%) 64.05 60.60 58.67 61.44 58.81 1.18
Crude protein (%) 74.31a 65.94b 60.67b 71.80a 61.34b 1.62
Crude fiber (%) 40.85a 33.99ab 27.18b 42.39a 30.75b 1.80
Ether extract (%) 80.77a 77.09ab 68.27c 78.15ab 73.82bc 1.33
Nitrogen-free extract (%) 76.89a 72.79ab 68.68b 75.41a 71.73ab 0.96
Digestible crude protein (%) 13.15a 11.37ab 10.33b 12.46a 10.46b 0.41
Total digestible nutrients (%) 58.33a 54.61b 48.80c 57.00ab 50.66c 1.03
Digestible energy*( kcal/kg) 2584.01a 2419.22b 2161.84c 2525.1ab 2244.23c 45.59
Ti: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave-treated wheat germ meal, T5: 40% autoclave-treated wheat germ meal. SEM: Standard error of the mean. Different superscript letters within the same row mean significant differences (p< 0.05). * Digestible energy = Total digestible nutrients* 44.3, according to Schneider and Flatt (1975).
Table 5. Carcass traits of New Zealand White rabbits (six weeks old) fed on autoclave-treated or untreated Wheat germ meal
Items Ti T2 T3 T4 T5 SEM
Carcass weight (%) 56.69a 55.43a 53.29b 55.69a 53.74b 0.37
Dressing (%) 60.38a 58.89ab 56.80c 59.52a 57.59bc 0.39
Liver (%) 2.91 2.42 2.60 2.91 2.89 0.09
Heart (%) 0.275 0.293 0.269 0.273 0.267 0.01
Spleen (%) 0.035 0.048 0.055 0.036 0.053 0.003
Kidney (%) 0.706 0.705 0.588 0.614 0.645 0.01
Giblets (%) 3.69 3.46 3.51 3.83 3.85 0.08
T1: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave-treated wheat germ meal, T5: 40%
autoclave-treated wheat germ meal. SEM: Standard error of the mean. Different superscript letters within the same row mean significant differences
(p<0.05)
Table 6. Meat quality of New Zealand White rabbits (six weeks old) fed on untreated or autoclave-treated wheat germ meal
Items Ti T2 T3 T4 T5 SEM
TAOC (mMg) 1.025ab 0.3800ab 0.465c 0.9200b 1.25a 0.085
MDA(mgg) 1.26d 3.17a 1.835c 1.815c 2.445b 0.162
Total cholesterol(mg/g) 13.50c 25.95a 12.85c 22.15b 12.85c 0.922
TAOC: Total Antioxidant Capacity MDA: Malondialdehyde.Ti: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ
meal, T4: 20% autoclave-treated wheat germ meal, T5: 40% autoclave-treated wheat germ meal. Different superscript letters within the same row mean
significant differences (P<0.05). SEM: Standard error of the mean.
Table 7. Blood constitutes of New Zealand White rabbits (six weeks old) with treated or untreated wheat germ meal
Items Ti T2 T3 T4 T5 SEM
Total protein (g/ dl) 5.44b 6.10a 5.59ab 6.10a 5.46b 0.10
Albumin (g/ dl) 2.82 2.96 2.90 2.69 2.75 0.05
Globulin (g/ dl) 2.62b 3.14a 2.69b 3.41a 2.71b 0.09
Total cholesterol (g/ dl) 83.75a 57.90b 75.17a 58.16b 53.56b 3.46
Total lipid (g/ dl) 311.90a 254.33b 290.87a 190.45c 187.49c 14.13
ALT(U/ L) 12.73 12.48 12.32 13.02 12.54 0.12
AST(U/ L) 16.22 15.01 14.70 15.44 15.02 0.25
T1: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave-treated wheat germ meal, T5: 40% autoclave-treated wheat germ meal. SEM: Standard error of the mean. Different superscript letters within the same row mean significant differences (p<0.05).
Table 8. Economic efficiency of New Zealand White rabbits (six weeks old) fed on diets with treated or untreated wheat germ meal_
Items Ti T2 T3 T4 T5
Total weight gain (kg) 1.498 1.363 1.200 1.467 1.292
Price of 1kg body weight 49 49 49 49 49
Selling price/rabbit (LE) (A) 73.40 66.78 58.85 71.88 63.31
Total feed intake 5.801 5.297 5.279 5.562 5.320
Price/kg feed (LE) 4.44 4.27 4.16 4.28 4.17
Total feed cost/rabbit (LE) (B) 25.75 22.61 21.96 23.80 22.18
Net revenue(LE)1 47.65 44.17 36.89 48.08 41.13
Economic efficiency2 1.85 1.953 1.679 2.02 1.854
Relative economic efficiency3 100 105.60 90.80 109.19 100.23
T1: control diet, T2: 20% untreated wheat germ meal, T3: 40% untreated wheat germ meal, T4: 20% autoclave-treated wheat germ meal, T5: 40% autoclave- treated wheat germ meal. LE: Egyptian pound. 1: Net revenue = A - B. 2: Economic efficiency = (A-B/B). 3: Relative Economic Efficiency= Economic efficiency of treatments other than the control/ Economic efficiency of the control group.
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DISCUSSION
Chemical composition
According to the results obtained in the present study, AWGM did not affect chemical composition of CP, CF, ash, and DE, while EE was decreased from 6.02 to 5.30% and lowered the anti-nutritional factor dry gluten by 50% and trypsin inhibitor activity by 62.4% compared to untreated WGM. Blair (2018) reported that WGM contains 250-300g/kg CP, 70-120 g/kg crude fat and 30-60 g/kg CF. Moran and Summers (1967) reported that raw WGM contains 29% CP, 2.1% CF, and 10.3% EE, and the content did not influence antitrypsin activity. It was also found that autoclaving of raw WGM for 90 min did not influence CP, CF, EE, ash, and DE contents but antitrypsin activity was degraded. Creek et al.
(1962) stated that autoclaving destroyed the activity of trypsin inhibitor and hemagglutinin factor. Also, Zhu et al. (2006) found that defatted WGM contains high amount of protein (34.9%) and has a well-balanced amino acids profiles. Parrish and Bolt (1963) declared that raw WGM contain gluten as an anti-nutritional factor.
However, Bayley et al. (1968) found that raw WGM contained 29% CP, 3.4% CF, 10.3% EE, while after autoclaving for 45 or 20 min decreased CP contain from 29% to 28.6 and 28.7%, respectively. Moreover, CF reduced from 3.4% to 2.9% and EE from 10.3% to 9.7%. While, Ceve et al. (1968) found that the pelleting process increased the nutritive value of raw WGM, particularly in ME values.
Growth performance
Values of final body weight, BWG, and FCR almost close to the values found in rabbits fed on the low level (20%) of treated or untreated WGM. However, at an increased untreated WGM in diet, significantly decreased final body weight and daily BWG and improved FCR. These results can be explained by Lawrence et al. (2002) who reported growth performance in pigs fed on diets containing wheat gluten at levels of 3, 6, 9 and 12% was not improved.
This decline in growth performance with increasing WGM level may be due to an increase in anti-proteolytic factor (trypsin inhibitor) which inhibit enzymatic digestion of proteins or other hemagglutinin factors (Creek and Vasaitis, 1962). Also, Moran and Summers (1967) found that anti trypsin activities were very high in raw WGM. Parrish and Bolt
(1963) confirmed the impairment of growth rate, feed efficiency and fat absorption in chicks as a result of feeding raw WGM and the presence of gluten. In addition, Creek et al. (1961) reported that when chicks fed raw WGM led to a reduction in growth rate and feed efficiency, accompanied by hypertrophy of the liver and impairment of the absorption of fat and protein. In the present study, FI was not significantly affected by dietary treatments. Moran and Summers (1967) studied the effects of WGM autoclaved at 121 °C for 20 minutes then incorporating to chicken diets at the level of either 47% or 63.8% and found an improvement in these groups in growth performance and feed utilization compared with other groups fed WGM autoclaved for 90 min and control group. Also, Ceve et al. (1968) found that addition of AWGM (autoclaving at 118 °C for 20 or 45 min) to broiler diet at a level of 33% improved BWG and FCR. Furthermore, Rafai et al. (2011) concluded that BWG of pigs was improved by 6% when they fed diet supplemented with fermented wheat germ extract at the level of 1g/kg of diet compared with the control group. Also, Ellakany et al. (2017) documented that incorporation of fermented wheat germ extract with Saccharomyces cerevisiae at levels of 0.5, 1.5 and 3 g/kg of diet increased body weight significantly in broilers, especially at the dose 3g/kg of diet.
Digestibility coefficient
The effect of experimental diets on digestion coefficient and nutritive values were in agreement with Moran and Summers (1967) who found denaturation of raw WGM increased digestibility because of decreased resistance to enzymatic degradation and destruction of toxic factors. Also, Nesheim et al. (1962) stated that fat absorption of raw soybean meal in chickens was improved by heat treatment. Moreover, similar processing of raw soybean enhanced meal digestibility from 64 to 88% in the cockerel (Nitsan, 1965) and from 54 to 89% for the laying hen (Nesheim and Garlich, 1966). Contrarily, Ceve et al. (1968) found that addition of 33% AWGM at 118 °C for 20 or 45 min) to broiler diet were significantly improved metabolizable energy and fat digestibility compared to those fed on raw WGM. Suliman et al. (2015) found an insignificant decrease in terms of digestion coefficients of CP, CF, and NFE when rabbits fed diets containing chemically and biologically treated castor meal at 20% as replacement of soybean meal.
Carcass characteristics
The results obtained in the current study was consistent with Duwa et al. (2014) who reported rabbit fed with 30% roasted sunflower seed meal indicated highest average values in terms of slaughter weight, carcass weight and dressing percentage in comparison to groups received 10, 20 % roasted sunflower seed meal and control group. While, there was no significant difference in liver, kidney, lung, and heart among the treatment groups. Gasmi et al. (2007) found that liver weight was not affected when rabbits fed with rapeseed meal (canola seed meal) replaced up to14% dietary soybean meal. On the other hand, Leeuw et al. (2009) detected no difference in carcass weight and dressing percentage when using 75 or 100% maize germ meal in steers diets. Ellakany et al. (2017) found that combination of fermented wheat
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germ extract with Saccharomyces cerevisiae at doses of 0.5, 1.5 and 3 g/kg of diet significantly increased the percentage of intestinal weight and decreased the weight of the liver and total body fat in broilers.
Meat quality
The supplementation of natural antioxidant in feed decreases lipid peroxidation and improves stability of meat. Consistently, Gnanasampandam and Zayas (2007) found that the addition of 7% wheat germ protein flour decreased the fat content in frankfurters. On the other hand, Arshad et al. (2013) found that combination of wheat germ oil and lipoic acid improves the quality of the broiler meat. Arshed et al. (2017) reported that nuggets were made from the leg meat of chickens fed with combination of a-lipoic acid (150 mgkg) and wheat germ oil (200 mgkg) showed maximum antioxidant power as well as stability during storage.
Blood constituents
In the present experiment, the results of blood constituents were in agreement with Ellakany et al. (2017) who found the incorporation of fermented wheat germ extract with Saccharomyces cerevisiae at rates of 0.5, 1.5 and 3 g/kg diet significantly decreased triglyceride level in blood. A significant decrease in AST concentration was observed at a dose of 1.5 g//kg of diet, while both doses of 1.5 and 3 g/kg of diet decreased significantly ALT level in the blood. In this respect, Louis et al. (1991) reported that blood lipid was decreased when adding small quantities of raw and defatted wheat germ in the rat diet.
Economic efficiency
Rabbit fed on the diets contained untreated or treated WGM at level of 20 % had higher economic return than control diets. These results were in agreement with Leeuw et al. (2009) who found lower feed cost when using 100% defatted maize germ meal in steers' diets.
CONCLUSION
It is concluded that untreated or autoclave-treated WGM can be used up to 20% in growing rabbit diets as a substitution for soybean meal protein without adverse effects in rabbit performance and an improvement in economic efficiency compared to those fed with 40% untreated or autoclave-treated WGM.
DECLARATIONS
Author's contributions
Dr. Walaa A. Salama designed the work and drafted the manuscript. Dr. Amira M. Refaie performed the statistical analysis, tabulation of the experimental data and chemical analysis. Dr. Hamdy F. Amin participated in review the manuscript and Dr. Lamiaa F. Abdel Mawla performed the practical part of the experiment.
Competing interests
The authors have declared that no competing interests exist. REFERENCES
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