الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
This study was carried out at Fish Culture Research Station at El-Kanater El-Khairia, Kalubia Governorate, Egypt. The study include two experiments, the first experiment was designed to determine the effect of three feeding rates (2, 4 and 6 % of fish body weight/d), two feeding frequencies (2 and 3 times/d), and two stocking densities (2 and 4 fish/m3) on the growth performance of Nile tilapia (Oreochromis niloticus). whereas, the second experiment aimed to investigate the effect of three protein/energy ratios (80, 100 and 120 mg CP/kcal ME), two CP levels (25 and 30%) and two lipid sources (sunflower oil, SFO and beef tallow, BT) on the growth performance of hybrid Nile tilapia (Oreochromis niloticus x Oreochromis aureus) .
The experimental fish were obtained from the El-Kanater El-Khairia, Fish Research Station hatchery. Fish of the first experiment had an average initial body weight of 39.2 g and were fed on a basal diet contained 30% CP and 3000 kcal ME/kg diet during the experimental period which continued for 22 weeks from 18 June until 19 November, 1997. While fish of the second experiment had an average initial body weight of 42.0 g and were fed on 12 experimental diets contained different PIE ratios, CP levels and lipid sources. The experiment started at 18 June and continued until 22 October 2000 (18 weeks). Fish growth performance, feed utilization and fish chemical composition were determined in both experiments:
Results obtained can be summarized as follows:
First experiment:
Final body weight (BW) and total weight gain ( G) of fish increased with increasing the level of feeding rate (FR) from 2% to 6% of total fish biomass. Differences in fin .I BW, and WG of fish fed 2% of their body weight and thos fed either 4% or 6% of their live body weight were ignificant (P<0.05), while those between fish fed 4% and 6 /0 of their body weight in either final BW or WG values were not significant. The differences in neither final BW n r WG of fish due to both feed frequency (FF) and stocki g density (SD) levels effects were not significant.
-The final body length (BL) of fish increased with eac increase in the FR level, the differences in final BL of fish ed 2% of fish biomass and those fed 4% or 6% of fish bio ass were significant (P<0.05), whereas the differences in fi al BL of fish fed 4% or 6% of fish biomass were not-significant. At the termination of the experimental period, the fi al BL of fish fed 2 times was 20.92 cm and that of fish fed 3 times/d was 20.96, the differences were not significant. Fi -h stocked at 2 fish/m3 had some what longest final BL (21.0 cm) than those stocked at 4 fish/m3 (20.86 cm), but the d fferences were not significant.
-Fish fed at 2% of fish biomass recorded the lowest ( <0.05) K value (1.69), while those fed at either 4% or 6 of fish biomass showed the same K value being 1.74. Feeding frequency level ( 2 or 3 times/d) and stocking densi level (2 or 4 fish/m3) had no significant effect on final K alues of Nile tilapia, being 1.73 and 1.72, respectively for bo h traits.
-Specific growth rate (SGR) increased as FR level i creased, being 0.81, 0.94 and 0.96 for fish fed 2, 4 and 6° of their
body weight, respectively. The differences were significant (P<0.05) only between fish fed 2% and those fed either 4% or 6% of their body weight. Feeding frequency and stocking density levels had no significant effect on SGR values.
-Feed conversion ratio’s (FCR’s) were 3.09, 5.89 and 7.78 for fish fed at 2, 4 and 6% of fish biomass, respectively, with significant differences (P<0.05) among all treatments. Fish fed 2 times/d had slightly higher FCR than those fed 3 times (5.72 viz 5.45), but the differences were not significant. whereas, fish stocked at 2 fish/m3 and 4 fish/m3 had nearly the same FCR value, 5.56 and 5.61, respectively .
Protein efficiency ratio (PER) decreased significantly (P<0.05) with each increase in the FR level. Values obtained were 1.36, 0.71 and 0.49 for fish fed 2, 4 and 6% of their body weight. Both feeding frequency and stocking density levels had no significant effect on PER values.
-Protein productive value (PPV) showed the same trend observed with PER where PPV averaged 25.68, 14.17 and 9.74% for fish fed 2, 4 and 6% of fish biomass, with significant (P<0.05) differences between all treatments. whereas no significant differences were detected in PPV’s due to either feeding frequency level or stocking density level effects.
-Energy retention (ER) followed nearly the same trend
observed with both PER and PPV, as values of ER decreased with increasing the FR levels, being 12.11, 7.09 and 6.42% for fish fed at 2, 4 and 6% of their body weight. The differences in ER values of fish fed 2% of their body weight and those of fish fed either 4% or 6% of their body weight were significant (P<0.05), whereas no significant differences
were observed between fish fed 4% and 6% of weight. Feeding frequency level and stocking de had no significant effect on ER values.
Hepato somatic index (HSI) for both males a decreased gradually with each increase in the F with no significant differences. Values of HSI for and females varied slightly according to t frequency level and the differences were not whereas, I ISI decreased significantly (P<0 increasing the stocking density from 2 fish/m3 to 4 both males and females.
- Fish fed 4% of their body weight showed the h values for both sexes, while those fed 6% of weight recorded the lowest value for males and th of fish biomass showed the lowest value for fe differences in GSI values due to FR levels for were almost significant. The feeding frequency 1 significant effect on GS! values for both males a whereas, these values decreased with increasing t density from 2 fish/m3 to 4 fish/m3 and the differ significant (P<0.05) only with males.
Increasing the FR level from 2% to 4% or 6% of fi had no significant effect on moisture, CP, and EE tilapia flesh, whereas increasing the FR from 2° fish biomass significantly (P<0.05) increased fis contents, then decreased (P<0.05) with increasi from 4% to 6% of fish biomass. Increasing frequency from 2 times/d to 3 times/d and stoc from 2 fish/m3 to 4 fish/m3 had no significan
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SUMMARY
chemical composition of fish flesh, except for moisture content which increased significantly (P<0.05) with increasing the feeding frequency from 2 times/d to 3 times/d.
- Based on results of the first experiment, it could be concluded that the best growth performance values of Nile tilapia were obtained with fish fed at a FR of 4% from total body weight daily, FF of 2 times/day and SD of 4 fish/m3.
Second Experiment:
Fish fed the 100 P/E ratio diet recorded the highest final BW and total WG, followed by those fed the 80 P/E ratio diet, whereas fish fed the 120 P/E ratio diet showed the lowest values. Differences in either final BW or WG between each P/E ratio and the others were significant (P<0.05). Increasing the dietary CP level from 25 to 30% significantly (P<0.05) increased both final BW and total WG of hybrid Nile tilapia. Fish fed beef tallow (BT) as source of lipid recorded the highest (P<0.05) final BW and WG, while those fed sunflower oil (SFO) achieved the lowest ones.
The longest final BL(21.94 cm) was recorded by fish fed the diet with 100 P/E ratio, whereas the shortest one (21.17 cm) was shown by fish fed the diet had the 120 P/E ratio, with significant (P<0.05) differences among all the P/E ratios studied. Fish fed the 30% dietary CP level achieved the longest final BL (21.75 cm) and those fed the 25% dietary CP level recorded the shortest one (21.54 cm). The differences in final BL of fish due to CP level effect were significant. Fish fed BT recorded the longest final BL (21.82 cm) and those
135
SUMMARY
fed SFO showed the shortest one (21.39 cm), with significant (P<0.05) differences between the two sources of lipid.
Fish fed the diets with either 80 or 100 P/E ratio recorded the highest (P<0.05) final K value being 1.71 for both ratios, whereas those fed the diet with the 120 P/E ratio achieved the lowest K value (1.67). Protein level (25 or 30%) and source of
lipid (BT or SFO) had no significant effect on final K values.
- Values of SGR increased with increasing the P/E ratio from 80 to 100, being 1.14 and 1.16, respectively, then decreased to reach 1.07 with increasing the P/E ratio to 120. The differences between each P/E ratio level and the others were significant (P<0.05). The highest SGR value (1.14) was recorded by fish fed the higher CP level (30), while the lowest value (1.11) was achieved by fish fed the lower CP level (25%), with significant differences between the two levels of CP. Fish fed BT as source of lipid recorded the highest (P<0.05) SGR value (1.15), whereas those fed SFO achieved the lowest value (1.10).
Fish fed the diet with 100 P/E ratio showed the best FCR value (3.22) followed by those fed the diet with 80 P/E ratio being 3.27, with no significant differences. whereas, fish fed the diet with 120 P/E ratio recorded the poorest (P<0.05) FCR value (3.44). Fish fed 30% CP recorded th best (P<0.05) FCR value (3.27), and those fed the diet with_ 25% CP showed the poorest value (3.35). Fish fed BT as source of lipid had better (P<0.05) FCR value than those fed SFO, being 3.25 and 3.37, respectively.
Values of PER decreased with increasing the P/E ratio from 100 to 120. Fish fed diets with 80 or 100 P/E ratio recorded the same (best) PER value (1.14), whereas those fed diet with
I”
120 P/E ratio showed the lowest, poorest (P<0.05) PER value (1.04). PER values decreased with increasing the dietary CP level. Fish fed the 25% dietary CP level recorded the best (P<0.05) PER value (1.19), while those fed the 30% dietary CP level showed the poorest one (1.03). Fish fed BT utilize their dietary protein contents more better (P<0.05) than those fed SFO, values of PER were 1.13 and 1.09, respectively.
-Protein productive values increased with increasing the P/E ratio, being 16.35, 16.57 and 17.47% for fish fed 80,100 and 120 P/E ratio levels, indicating that fish utilize the dietary protein more efficient with each increase in the dietary P/E ratio level. The differences in PPV’s were only significant (P<0.05) between the 120 P/E ratio and 80 P/E ratio levels. The best (P<0.05) PPV (17.62%) was recorded by fish fed the lower dietary CP level (25%), whereas those fed the higher dietary CP level (30%) achieved the poorest PPV (15.97%). The source of lipid
(BT or SFO) had no significant effect on PPV’s.
-Values of ER increased with increasing the P/E ratio level, being
8.39, 9.64 and 10.04% for fish fed diets with 80, 100 and 120 P/E ratio levels, respectively, indicating that fish fed the higher P/E ratio diet retained more energy than those fed the lower P/E ratio diets. The differences in ER values between the three WE ratio levels were significant (P<0.05). Fish fed the lower protein level (25% CP) retained more energy (P<0.05) than those fed the higher level (30%) being 10.16 and 8.56%, respectively. Fish fed BT had higher (P<0.05) ER value than that of fish fed SFO, 9.63 and 9.09%, respectively.
-The HSI values decreased as th P/E ratio level increased from 80 to 100, then increased with increasing the P/E ratio level
from 100 to 120, but the differences were not sly ificant. The differences in HSI values due to either CP level 25% or 30) or source of lipid (BT or SFO) were not significa t.
- Fish fed the diet with the 120 P/E ratio level ecorded the highest (P<0.05) GSI value (0.65), while those ed the diets with the 80 and 100 P/E ratio levels achieved ne ly the same GSI values being 0.33 and 0.34, respective) , with no significant differences between these values. Bot dietary CP level (25 or 30%) and source of lipid (13T or S .0) had no significant effect on GSI values of hybrid Nile tila ia.
- Fish fed the higher PIE ratio (120) achieved the high t moisture and protein (P<0.05) contents, but the lowest fat <0.05) and ash percentages. While, fish fed the diet with lower P/E ratio (80) recorded the highest fat (P<0.05) content an the lowest protein percentage. Fish fed the diet with PIE ratio of 100 had the highest ash (P<0.05) content and the low .t moisture
percentage. Fish fed the lower CP level (25%) r highest moisture and fat (P<0.05) contents, and protein and ash (P<0.05) contents. whereas, th higher CP level (30%) achieved the highest prot (P<0.05) percentages and the lowest moisture and percentages. The highest (P<0.05) protein percent lowest moisture, fat (P<0.05) and ash contents wer fish fed SFO as source of lipid, whereas those fed the highest moisture, fat (P<0.05) and ash conte lowest (P<0.05) protein percentage.
- from the results of the second experiment, it can be co eluded that hybrid Nile tilapia fish fed the diet with 100 P/E ratio, 0% CP and 7% 13T recorded almost the best growth performance va ues.
corded the the lowest se fed the in and ash t (P<0.05) ge and the shown by T recorded ts, but the.