الفهرس 
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Abstract
This study was carried out at a commercial fish farm located in Kafr El-Shiekh Governorate, Egypt, where started at the second week of May 2015 and terminated at the third week of September (135 days period). Yellow corn and soybean meal as main sources for energy and plant protein, respectively, were replaced by either DDGS or Foots. Two feeding experiments were carried out to investigate the effects of partially replacing of yellow corn and soybean meal with the tested materials on growth performance, body composition and nutrients digestibility of monosix Nile tilapia (Oeochromis niloticus) fingerlings.
Two feeding experiments were carried out, the first experimental diets, were conducted to replace the yellow corn as a main source of energy in the control diet by DDGS or Foots, and were formulated almost isonitrogenous (25 to 25.84% crude protein) and isoenergetic (4442.34 to 4748.65 Kcal GE/ kg). The second experimental diets, were formulated to replace soybean meal as a main source of plant protein in the control diet by DDGS or Foots and were almost isonitrogenous (24.93 to 25.09 % crude protein) and isoenergetic (4437.11 to 4602.32 Kcal GE/kg). At the first experiment, yellow corn was replaced by 0, 20 and 40% of DDGS or Foots (TC1, TC2 TC3 TC4 and TC5, respectively). While, at the second experiment, soybean meal was also replaced by 0, 20 and 40% of either DDGS or Foots (TP1, TP2, TP3, TP4 and TP5, respectively).
Seven hundred and fifty tilapia fingerlings were randomly divided into two experiments. Each experiment contained five different groups with three replicates of 25 fingerlings (initial weight 10 ± 0.05 g). During the feeding period (18 week), fish were hand-fed 3% of initial body weight, two times a day (08:30, 16.30) for two weeks. Increasing palatability of the diets was observed in all treatments. Therefore, the feeding ratio was increased to 3.5% until the end of the experiments. The daily amount of feed was subdivided into two equal feeding meals. The fish were weighed once every 2 weeks and the amount of the diet fed was adjusted accordingly.
After the feeding experiments had finished, digestibility trials were concluded using CF as internal marker. Records obtained included weight gain, ADG, SGR, FCR, RGR, retained nutrients, PER, PPV, FPV, EU and water quality measurements. The corn processing by-products, distillers dried grains with solubles or Foots, were assigned for the summative analysis, determination of amino acids and fatty acids. Finally, the two experiments were evaluated economically by calculated the feed costs for producing one Kg of the fish gain in weight.
Results obtained from feeding experiments could be summaries in the following:
In comparison with yellow corn, the CP, EE and CF contents of DDGS or Foots were higher than that showed for yellow corn. In contrast, when compared with soybean meal, the CP content of the tested materials was lower. Concerning the EE and CF content they were higher in the tested materials than soybean meal. Also, the tested materials were higher in GE content when comparing with yellow corn or soybean meal.
Both of DDGS and Foots showed higher contents of amino acids, iso-leucine, leucine, lysine, phenylalanine, tyrosine, threonine, valine, methionine, arginine and histidine and lower in cysteine, than those of yellow corn. However, DDGS and Foots had lower contents of the same measured amino acids than those of SBM unless tyrosine. Yellow corn had higher contents of the all tested fatty acids palmitic, stearic, oleic, linoleic, linolenic more than those of soybean meal. Distillers dried grains with solubles (DDGS) had higher content of all tested fatty acids more than yellow corn and soybean meal. Therein Foots showed higher content of linoleic acid and palmitic acid more than DDGS, Soybean meal and yellow corn.
The first experiment
1- Dry matter digestibility coefficients showed significant differences between the control diet (the highest value) and all experimental treatments except TC5. The lowest value was obtained in TC5 (87.63%) where, 40% of corn was replaced by Foots. In respect to the digestibility coefficient of CP, EE, NFE and energy, TC2 recorded the highest values (75.76, 89.86%, 57.48 and 68.71%), respectively, followed by TC3 with significant differences. Whereas, the lowest digestibility coefficient values of CP, NFE and energy were obtained by TC5 being 59.20, 36.43 and 52.60%, respectively but the control diet has the lowest digestibility coefficient value of EE (67.83%).
2- Results showed no significant differences (P˃0.05) between TC1 control, TC2 (20% DDGS) and TC3 (40% DDGS) regarding to feed intake, CP and energy intake values, however the differences between the control diet and TC4 (20% Foots) and TC5 (40% Foots) were significant. Data also showed that TC5 recorded the lowest significant intake of feed, CP, EE, NFE and energy with no significant differences with TC4. Variations on EE and NFE intake were not significant between the control diet and TC2. The variations were significant (P˂0.05) between the control diet, TC3, TC4 and TC5. Also, the data indicated that feed and nutrients intake were significantly decreased as corn was partially replaced by Foots more than the DDGS.
3- Growth performance parameters illustrated that the highest values of WG, ADG, SGR and RGR were observed in fish fed the control diet (TC1) followed by those fed diets TC2, TC3. The lowest values of the same parameters were noticed in TC5. However, there were no significant differences (P˃0.05) between TC2, TC3 and TC4 regards final weight, weight gain (WG), ADG, SGR and RGR. Also the differences between TC3, TC4 and TC5 were not significant (P˃0.05).
4- The results of chemical composition and energy content of fish showed that the highest CP content (55.73%) was detected in TC3 followed by TC5 (54.93%) and TC2 (53.45%), while, the lowest one was observed with fish feed the control diet (50.21%). The highest value of ether extract content of carcass was recorded with fish group fed TC1 followed by TC4 and TC5 (P˂0.05) being (16.90%), (16.61%) and (16.16%), respectively. The lowest EE content was shown with fish carcass fed TC2 (14.00%) followed by TC3 (15.70). The highest energy content (5066.82 Kcal/kg) was obtained by (TC5), followed by the control TC1 and TC4, while the lowest one was obtained by TC2. The highest (P˂0.05) ash content (19.77%) was recorded for TC2 while the lowest one (17.79%) was observed in TC5.
5- The highest significant (P˂0.05) amount of protein retention was noticed in TC3 followed by the control diet and TC2, being 8.21, 7.71 and 7.54 g/ fish, respectively. The lowest protein retention was observed by TC4 (7.01 g/fish) followed by TC5 (7.21 g/fish), the differences were not significant. Also the results indicated that the control diet had the highest value of fat retention (2.76 g/fish) followed by TC3 (2.42) and TC4 (2.37), while the lowest fat retention value was obtained by TC2 (2.12) followed by TC5 (2.23). Fish group fed the control diet (TC1) had the highest energy retention value compared to the other fish fed tested diets. Regarding the ash retention, there were no significant differences between the control diet, TC2 and TC3 in which the highest value (2.79 g/fish) was recorded with the fish group fed TC2. Also no significant differences were recorded between TC4 and TC5, the lowest value was shown in TC5 (2.11 g/fish).
6- The best (FCR) being 1.82 followed by 1.86, were recorded respectively, by fish given TC4 (20% Foots) and TC5 (40% Foots). Whereas, the same worst value (P˃0.05) was obtained by fish group fed the control diet and the TC2 (2.02) followed by TC3 (2.00). Indeed, the results indicated that there were significant differences (P˂0.05) concerning FCR values between the control diet, TC4 and TC5, since FCR values were improved. Moreover, within the fish fed diets contained DDGS (TC2 and TC3), FCR were not significantly different. Values of PER followed the same trend as those of FCR. The highest significant value of PPV was obtained by TC5 followed by TC3 and then TC4. Also, there were no significant differences between fish fed the control diet and fish fed the TC2 diet. The fish fed TC4 showed the best FPV improvement followed by the fish fed the control diet and then TC5 (P˂0.05), with no significant differences. The lowest FPV value was observed by the fish fed TC2 followed by TC3. Fish fed TC4 showed the highest EU followed by TC5 with no significant differences being 13.34 and 13.23%. The lowest (P˂0.05) value of EU was attended in fish fed TC2 (20% DDGS).
7- The lowest feed cost per unit of fish gain was recorded in the diets that replaced yellow corn by 40% Foots (4.81 L.E) followed by 20% Foots (5.13 L.E). The highest feed cost for producing one Kg fish gain was recorded for control diet (6.14 L.E) followed by the diets replaced yellow corn by 20% of DDGS (6.02 L.E) and then 40% DDGS (5.36 L.E).
The second experiment
1. Fish fed on the control diet (TP1) recorded the highest significant digestibility of CP, NFE and energy. As the level of Foots was increased from 20 to 40% the digestibility of DM, CP, EE, NFE and energy were significantly increased. However, as the levels of DDGS was increased from 20 to 40% the digestibility of DM and EE were increased (P˂0.05) and the digestibility of CP, NFE and energy were decreased (P˂0.05).
2. The control diet consumed significantly higher feed (137 g/fish) than the other treatments. The lowest feed intake (105.42 g/fish) was recorded for TP3. There was significant (P˂0.05) decreasing feed intake for TP2, TP4 and TP5. There were significant decrease (P˂0.05) between TP2 and TP4 with respect to feed intake and all nutrients consumption. Meanwhile, the differences were significant between the substitution levels of Foots (TP4 and TP5) concerning CP, NFE and energy intake, but non-significant with respect to feed and EE intake. Also control group showed significant highest intake of feed, CP, NFE and energy compared with the other experimental treatments. The data showed that TP3 recorded significant lowest intake of feed, CP, NFE and energy.
3. The control treatment had significant (P˂0.05) the highest final body weight (FBW), weight gain (WG), daily gain (ADG), specific growth rate (SGR) and relative growth rate (RGR) followed by TP2 and then TP4 while the lowest corresponding values were shown for TP3 followed by TP5. The differences were not significant (P˃0.05) either between TP2 and TP4 or between TP3 and TP5 regard FBW, WG, ADG and RGR values. Values of SGR had no significant difference between TP3 and TP5 but significant between the other treatments.
4. Results showed significant lower DM, CP, EE and energy for treated fish than those of control. However, ash contents were significant higher than control. The decreasing in CP content was significant with increasing the substitution levels (20% to 40%) of soybean meal by either DDGS or Foots. Therein, the significant lowest (P˂0.05) CP content (49.57%) was observed in (TP5). The results showed also that control treatment recorded significant (P˂0.05) higher EE and energy content than the other experimental treatment whereas, TP4 showed the lowest significant EE value. The decreasing in EE content was not significant between TP3 and TP4. Meanwhile, there was significant lower energy content of treated Nile tilapia than that of control.
5. The significant (P˂0.05) highest protein, fat, ash and energy retention were obtained with fish fed the control diet (TP1). Meanwhile, the lowest CP values were noticed by TP5. As the levels of both DDGS and Foots were increased from 20 to 40%, protein, fat, ash and energy retention were significant (P˂0.05) decreased.
6. The best significant (FCR) was obtained from fish fed the control diet (TP1) followed, by TP2 being 1.89 and 1.98, respectively. However, the worst feed conversion ratio (2.07) was recorded for fish fed TP5 followed by TP3 (2.03) with no significant differences. The same trend was observed with PER values. Fish fed TP4 recorded the highest PPV value (24.80%) followed by control (23.30%) with no significant differences. Fish fed TP5 recorded the lowest PPV followed by TP2 being 19.61 and 20.61%, respectively. The highest FPV value was obtained from fish fed the control diet with significant differences when compared with the other groups. Meanwhile there were no significant decrease (P˃0.05) among all other experimental treatments. Fish fed the control diet showed the highest significant EU (13.76%) followed by fish fed TP4 (12.56%), since the lowest energy utilization value (11.64%) was obtained in fish fed TP2. Differences between the experimental groups were significant, except that between TP3 and TP5 was not significant (P˃0.05).
7. The control diet (TP1) was the highest cost of one ton feed followed by TP2 and TP3. The lowest cost of one ton feed was recorded by TP5 followed by TP4. However, the highest cost needed for producing one Kg fish gain was observed by diet that replaced soybean meal by 40% followed by 20% of DDGS (6.06 and 5.92 L.E), respectively. The lowest cost needed for producing one kg fish gain (5.75 L.E) was recorded for the control followed by 20% Foots (5.88 L.E) and 40% Foots (5.89 L.E). However the highest cost was noticed for 40% DDGS (6.06 L.E) followed by 20% DDGS (5.92 L.E).
In conclusion
The results of the experiments concluded that 20% DDGS or Foots can be included in Nile tilapia diets as a replacement of yellow corn and soybean meal without any negative effects on growth performance.
On the economical point of view, in case of unavailability of yellow corn and soybean meal or their high price, DDGS or Foots could be recommended to replace up to 40% of the yellow corn and replaced up to 20% of soybean meal by either of the tested materials to decrease feeding cost of Nile tilapia (O. niloticus) fingerlings.