Live body weight and daily body gain of Nile tilapia fish decreased significantly (P<0.001) with increasing dietary lead level. Live body weight and daily body gain of Nile tilapia increased significantly with vitamin E or calcium supplementation in diets. Fish fed diets supplemented with calcium recorded higher body weigh and growth rate than the other experimental groups. Daily feed intake decreased significantly with increasing dietary lead level. Increasing dietary lead level impaired the feed conversion during the whole experimental period. Vitamin E and calcium supplementation in fish diets significantly (P<0.05) increased feed intake and improved feed conversion insignificantly. Within each lead level, daily feed intake slightly increased and feed conversion improved with the Vitamin E or calcium supplementation during the whole experimental period (0 to 4 months). Blood hemoglobin, serum total protein, albumin were significantly (P<0.001) decreased, while urea-N and creatinine, AST and ALT significantly (P<0.001) increased with increasing dietary lead level. Blood hemoglobin, serum total protein, albumin were significantly (P< 0.01 or 0.001) increased, while urea-N, creatinine, AST and ALT significantly (P<0.05 or 0.001) decreased with vitamin E or calcium supplementations in fish diets. Blood hemoglobin, serum total protein, albumin, globulin, creatinine and AST were insignificantly affected by the interaction between lead level and dietary supplementation, while urea-N and ALT levels were significantly (P<0.05) affected. Body moisture and ether extract contents were significantly (P<0.01) decreased, while protein content was significantly (P<0.05) increased by increasing dietary lead level. Body ash did not affected by dietary lead level. Ether extract contents were significantly (P<0.01) increased, while protein contents were significantly (P<0.05) decreased by dietary supplementation. Body composition did not affected by the interaction between lead level and dietary lead level. Body lead residues increased significantly (P<0.001) by increasing lead level in fish diets. Vitamin E and calcium supplementation significantly (P<0.01) decreased lead residues in fish bodies.

Keywords: Toxicity; lead; Vitamin E; calcium; growth; feed conversion; blood components; body composition; residuals.

Most fish can tolerate environmental conditions that differ somewhat from the natural conditions in which they evolved. This does not mean, however, that they will be as healthy or live their full normal life span. Increased stress reduces a fish's ability to ward off diseases and heal itself. In addition, stress reduces a fish's ability to breed successfully and shortens its natural life span. A small amount of stress by itself is not usually fatal, but as stress levels increase, the fish ability to cope with it decreases. Thus, one of the most important goals of a fish keeper is to remove sources of stress wherever possible. Lead particles can enter the food supply through a number of routes. Lead-containing particles in air can deposit onto plants during harvesting, processing and distribution. Some agricultural pesticides also contain lead-based compounds which might remain as residues on crops (WHO, 1995). Lead is a bone-seeking element, also tissues other than bone are storage sites for lead in fish (Sorensen, 1991).  Highways pose a threat to fish because of lead contamination from automobile exhausts (Van Hassel et al., 1980 and Ney and Van Hassel, 1983). Carpenter (1930) reported that young stages of fish are more susceptible to lead than adults because small fish have higher metabolic rates. High levels of lead in the fish bodies can suffer from damage in the brain and nervous system, slowed growth, cause reproductive problems and digestive problems (Crandall and Goodnight, 1963 and Katz, 1979). Lead can be absorbed by the body and take the place of iron, calcium, or zinc. Fish get enough iron, calcium and zinc intake will absorb less lead (Jones, 1964, Weir and Hine, 1970 and Holcombe et al., 1976). The maximum acceptable toxicant limit (MATC) for inorganic lead has been determined for several species under different conditions and results range from 0.04 mg/l to 0.198 mg/l (WHO, 1995). The daily safe level for lead consumption in human food is 450 µg (WHO, 1972). Lead is accumulated mostly in gills, liver, kidneys, and bone (Holcombe et al., 1976, Merlini and Pozzi, 1977, Reichert et al., 1979 and WHO 1995).  Acute toxicity to fish can occur at concentrations of dissolved lead above the proposed EQS of 10 microgram/l^-1 in the water column. A lower guideline value of 0.5 µg/l of dissolved lead has been suggested by Grimwood and Dixon (1997).

The objective of the present study was to investigate the effects of dietary lead contamination and its amelioration by using dietary vitamin E and calcium supplementations on growth performance, feed efficiency, blood components and body composition of young Nile tilapia fish.

The study was conducted at the Department of Animal Production, Faculty of Agriculture, Zagazig University. Young Nile tilapia (Oreochromis niloticus) averaged about 6.7 g in weight raised in Abbassa Fish Hatchery were used in this study. The fish were stocked in twenty seven glass aquaria (70 X 40 X 60 cm) supplied with fresh aerated tap water. Fish were divided into nine groups, each group of fish was stocked into 3 aquaria and each contains 20 fishes. All fish groups were fed on basal pelleted diet consistent of fish meal 8.0%, soybean meal 28.0%, corn 14.0%, wheat bran 14.0%, alfalfa hay 33.0%, minerals mixture 0.5%, vitamin mixture 1.5% and carboxymethyl cellulose 1.0%. The chemical composition of the diet was crude protein 25.9%, ether extract 2.7%, crude fiber 8.7% and gross energy 3350.4 Kcal/Kg.

The fish of the first three groups were fed the normal diet, the other three groups were fed on the basal diet contaminated with 100 mg lead (lead oxide) /kg diet and the other three groups were fed on the same diet contaminated with 200 mg lead/kg diet. Fish were fed one time daily at a feeding rate of 3% of body weight per day. The total duration of the experimental feeding trial was 4 months (from May to September, 2002). Within each dietary lead level, the first group was fed the diet without supplementation the second was fed on the diet supplemented with 50 mg vitamin E per kg diet and the third group fed on the diet supplemented with 5 g calcium (calcium carbonate) per kg diet. Fish wastes were siphoned out and 25% of the water in each aquarium was removed daily and replaced with fresh new water. Fish were individually weighed to the nearest 0.1 gm at the beginning of the experiment and at biweekly intervals throughout the experimental period. Blood samples were taken from the caudal vein from three fish in each group which randomly selected for collecting blood samples. The hemoglobin was measured in the blood. The blood samples were centrifuged at 3000 RPM for 20 min. to separate the serum. Total protein, albumin, urea-N, creatinine and serum transaminase enzymes (AST; aspartate amino transferase and ALT; alanine amino transferase) were measured in blood serum by colormetric methods using commercial kits. Proximate chemical compositions of experimental diets and the whole fish body were determined according to AOAC (1980). The lead content in the tissues were determined by using the atomic absorption spectrophotometric technique according to Nation and Robinson (1971). About 0.3 - 0.5 g of each sample was digested by using 5 ml of acid mixture (nitric acid : perchloric acid : sulfuric acid 3 : 2 : 1, respectively) in long necked Kjeldahl flask. The cooled acids mixture was added to the sample and heated slowly to encourage smooth digestion without charring. When the contents of the flask become colorless, the flasks were cooled and the contents were transferred quantitavely in a 25 ml volumetric flask with deionizer water.

The obtained data were statistically analyzed by 3 X 3 factorial design and evaluated by using the following model (Sendecor and Cochran, 1982):

Y_ijk = µ + L_i + V_j + LV_ij + E_ijk

Where, µ is the overall mean, L_i is the fixed effect of i^th dietary lead level, V_jj is the fixed effect of j^th dietary supplementation, LV_ij is the interaction effect of i^th dietary lead level and j^th dietary supplementation and E_ijk is the random error. Differences between treatments were statistical tested by Duncan'^,s multiple range test ( Duncan, 1955).

Live body weight and daily body gain of Nile tilapia fish decreased significantly (P<0.001) with increasing dietary lead level (Table 1). Fish group fed diets contaminated with 200 mg lead/kg diet recorded the lowest (P<0.05) live body weight and weight gain. Fish fed diets containing 100 or 200 mg lead/kg diet recorded lower live body by 9.24 and 16.90%, respectively than those fed diets without lead contamination after 4 months of the experimental period. On the other hand, daily body weight gain at the end of the experimental period decreased by 13.27 and 24.78%, respectively. Fish groups fed diets supplemented with calcium recorded higher body weigh and body gain. In this connection, Crandall and Goodnight (1963) and Katz (1979) reported that the high levels of lead in the fish diets slowed growth rate.

Live body weight and daily body gain of Nile tilapia increased significantly with vitamin E or calcium supplementation in diets (Table 1). Supplementation of the fish diet with vitamin E or calcium increased level body weight by 4.42 and 10.10%, respectively, and increased daily body gain by 6.59 and 17.58%, respectively, as compared with those fed diets without supplementation during the whole experimental period.

The interaction between dietary lead level and dietary supplementation did not show any significant differences in live body weight or daily body gain, except on live body weight at the second month (Table 1). Within each lead level, live body weight and daily body gain increased in fish groups fed diets supplemented with vitamin E or calcium compared to those fed diets without supplementation. Fish fed diets supplemented with calcium recorded higher growth rate than the other experimental groups.

Daily feed intake decreased significantly with increasing dietary lead level. Increasing dietary lead level impaired the feed conversion during the all experimental periods (Table 2). Fish fed the high lead level recorded the lower feed intake and higher feed conversion ratio during the whole experimental period. Feed conversion impaired by 11.86 and 25.54%, respectively, in fish group fed diets containing 100 or 200 mg lead/kg diet during the whole experimental period. Crandall and Goodnight (1963) and Katz (1979) reported that the high levels of lead in the fish diets decreased the digestibility.

Vitamin E and calcium supplementation in Nile tilapia fish diets increased feed intake significantly and improved feed conversion insignificantly during the whole experimental period. Fish fed the diets supplemented with 5 g calcium recorded the best feed conversion during the whole experimental period (Table 2).

The interaction between dietary lead level and dietary supplementation did not show any significant differences in daily feed intake or feed conversion except in feed intake during the period from 2 to 4 months of the experimental period (Table 2). Within each lead level, daily feed intake was slightly increased and feed conversion improved with the Vitamin E or calcium supplementation at 0-4 month of the experimental period. Fish groups fed diets supplemented with 5 g calcium recorded the best feed conversion than the other experimental groups.

Blood hemoglobin, serum total protein, albumin significantly (P<0.001) decreased, while urea-N and creatinine (as indicator of kidney function), AST and ALT (as indicator of liver function) significantly (P<0.001) increased with increasing dietary lead level, while globulin was insignificantly affected (Tables 3 and 4). Increasing the level of AST and ALT in the serum of fish fed diets contaminated with lead may reflect the impaired to the liver functions due to its role of lead detoxification. Also, the results obtained indicated that the kidney function (urea-N and creatinine level in the serum) increased with the increasing dietary lead level and decreasing the protein synthesis in the liver.

Blood hemoglobin, serum total protein, albumin significantly (P< 0.01 or 0.001) increased, while urea-N, creatinine, AST and ALT were significantly (P<0.05 or 0.001) decreased with vitamin E or calcium supplementation in fish diets, while globulin insignificantly affected (Tables 3 and 4).

Blood hemoglobin, serum total protein, albumin, globulin, creatinine and AST insignificantly affected by the interaction between lead level and dietary supplementation, while urea-N and ALT were significantly (P<0.05) affected (Tables 3 and 4).

Body moisture and ether extract contents were decreased significantly (P<0.01), while protein content increased significantly (P<0.05) by increasing dietary lead level. Body ash did not affected by dietary lead level (Table 5). In fish group fed 100 mg lead, fish fed diet supplemented with vitamin E or calcium decreased lead residue in fish body by 29.75 and 25.82%, respectively, than those fed diets without supplementation. The same figures were observed in fish fed diets supplemented with 200 mg lead which were 11.62 and 25.83%, respectively.

Ether extract content was increased significantly (P<0.01), while protein content was significantly (P<0.05) decreased by dietary supplementation. Body moisture and ash did not affected by dietary supplementation (Table 5).

Body composition did not significantly affected by the interaction between lead level and dietary supplementation (Table 5).

Body lead residues increased significantly (P<0.001) by increasing lead level in fish diets (Table 5).

Vitamin E and calcium supplementation decreased significantly (P<0.01) lead residues in fish bodies (Table 5). On the other hand, the interaction between lead level and dietary supplementation affected insignificantly body lead residues (Table 5). Based on the results obtained in this study it can be concluded the calcium or vitamin E dietary supplementations reduced and ameliorate the hazards of lead pollution in fish farms. Fish get enough calcium or vitamin E will absorb less lead.

Mortality rate linearly increased with increasing lead concentration in fish diet. Mortality rate increased with 125.0 and 175.0%, respectively in fish group fed diets contaminated with 100 and 200 mg lead/kg diet when compared with those fed diets without lead contamination. Mortality rate in fish group received diet without any supplementation recorded high mortality rate, while in fish group fed diets supplemented with vitamin E and calcium recorded lower mortality rate than those fed diets without supplementation (Table 6).

AOAC. 1980. Official Methods of Analysis, 13^th Edition. Association of Official Analytical Chemists, Virginia.

Carpenter K.E. (1930). Further researches on the action of metallic salts on fishes. Journal of Exp. Zool., 56: 407.

Crandall C.A. and Goodnight C.J. (1963). The effects of sublethal concentrations of several toxicants to the common guppy, Lebistes reticulates. Trans. Amer. Fish. Science, 82: 59.

Duncan, D.B. 1995. Multiple range and multiple F-test. Biometrics, 11:1-42.

Grimwood, M. and Dixon, E. (1997). Assessment of risks posed by List II metals to Sensitive Marine Areas (SMAs) and adequacy of existing environmental quality standards (EQSs) for SMA protection. WRC Report CO 4278.

Holcombe G.W., Benoit D.A., Leonard E.N. and McKim J.M. (1976). Long-term effects of lead exposure on three generations of brook trout (Salvelinus fontinalis) Journal of Fish. Res. Bd. Can., 33: 1731.

Jones J.R.E. (1964). Lead, zinc and copper: "The coagulation film anoxia" theory, Fish and River Pollution. Butterworth Co., London.

Katz M. (1979). The effects of heavy metals on fish and aquatic organisms In Metal Pollution in Aquatic Environments. Forstner V. and Wittman G.T. (Editors), Springer-Verlag, Berlin, p. 25.

Merlini M. and Pozzi G. (1977). Lead and freshwater fishes. 1. Lead accumulation and water pH. Envir. Poll., 12: 167.

Nation . L. and Robinson F.A. (1971). Concentration of some major and trace elements in honeybee, royal jelly and pollen, determined by atomic absorption spectrophotometer. Ournal of Apic Research, 10 (1): 35-43.

Ney J.J. and Van Hassel J.H. (1983). Sources of variability in accumulation of heavy metals by fishes in a roadside stream. Arch. Environ. Contam. Toxicol., 12: 701.

Reichert W.L., Fiderighi D.A. and Malins D.C. (1979). Uptake and metabolism of lead and cadmium in coho salmon (Oncorhynchus kisuth). Comp. Biochem. Physiol., 63C: 229.

Snedecor, G.W., Cochran, G.W., 1982. Statistical methods. 6^th edition. The Iowa State University, Press Ames, USA.

Sorensen Elas M.B. (1991). Metal Poisoning in Fish. CRC Press Inc., 2000 Corporate Blvd., N.W., Boca Raton, Florida, 33431, USA.

Van Hassel J.H., Ney J.J. and Garling D.L. (1980). Heavy metals in a stream ecosystem at sites near highways. Trans. Amer. Fish. Science, 109: 636.

WHO. (1972). Evaluation of mercury, lead, cadmium and the food additives amaranth, diethylpyrocarbonate and octyl gallate. World Health Organisation, Geneva 16^th Rep. Joint FAO/WHO Expert Committee on Food Additives, WHO Techn. Rep. Serv. No. 505.

WHO (1995). Environmental Health Criteria No 165, Lead, inorganic. IPCS, World Health Organization, Geneva.

Wier P.A. and Hine C.H. (1970). Effects of various metals on behavior of conditioned goldfish. Arch. Environ. Health, 20: 45.

 

Table 1. Live body weight (g) and daily body weight gain (g/day) of tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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                                   Body weight at                                                   Daily gain at

Items              M0                  M2                  M4                 0-2M                 2-4M               0-4M

__________________________________________________________________________________

Lead level in diets (mg/kg diet):

0          6.74±0.29      12.48±0.11^a     20.24±0.24^a  0.096±0.004    0.129±0.004^a   0.113±0.003^a

100      6.67±0.27      12.15±0.17^ab    18.37±0.31^b  0.092±0.005    0.104±0.003^b   0.098±0.004^b

200      6.63±0.27      11.74±0.35^b     16.82±0.34^c  0.085±0.006    0.085±0.005^c   0.085±0.004^c

Significant       NS                   **                   ***                  NS                ***                    ***

Dietary supplementation:

Without 6.72±0.30     11.55±0.31^a     17.63±0.59^a  0.080±0.005^a   0.101±0.006^a   0.091±0.006^a

Vit. E   6.74±0.28      12.34±0.13^b     18.41±0.47^b  0.093±0.005^ab 0.101±0.007^a   0.097±0.004^a

Calcium 6.58±0.25     12.48±0.13^b     19.41±0.49^c  0.099±0.003^b  0.115±0.009^b   0.107±0.004^b

Significant       NS                  ***                  ***                    *                    *                       **

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without 6.81±0.42     12.42±0.15^ab   19.73±0.44   0.094±0.006    0.122±0.009    0.108±0.007

Vit. E   6.80±0.54      12.58±0.27^a     19.95±0.12   0.096±0.009    0.123±0.003    0.110±0.004

Calcium 6.62±0.72     12.45±0.20^ab    21.05±0.10   0.097±0.010    0.143±0.003    0.120±0.005

100 mg lead:

Without 6.73±0.53     11.70±0.19^b     17.38±0.30   0.083±0.006    0.095±0.007    0.089±0.006

Vit. E   6.72±0.69      12.15±0.17^ab    18.42±0.29   0.091±0.011    0.104±0.002    0.098±0.006

Calcium 6.56±0.31     12.62±0.18^a     19.31±0.23   0.101±0.002    0.112±0.001    0.106±0.001

200 mg lead:

Without 6.62±0.77     10.53±0.40^c     15.77±0.47   0.065±0.073    0.087±0.007    0.076±0.007

50 mg  6.71±0.37      12.28±0.23^ab    16.85±0.32   0.093±0.010    0.077±0.006    0.084±0.005

Calcium 6.57±0.33     12.42±0.33^ab    17.85±0.15   0.098±0.002    0.091±0.013    0.094±0.006

Significant       NS                    *                     NS                   NS                 NS                     NS

__________________________________________________________________________________

M = Month

NS = Not significantly, * P<0.05, ** P<0.01 and  *** P<0.001.

Means in the same column within each classification with different letters differ significantly (P<0.05).

 

 

Table 2. Daily feed intake (g/day) and feed conversion ratio (g feed/1 g gain) of Nile tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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                             Daily feed intake (g) at                           Feed conversion (g feed/g gain) at

Items            0-2 M              2-4 M            0-4 M                   0-2 M         2-4 M                0-4 M

_________________________________________________________________________________

Lead level in diets (mg/kg diet):

0        0.236±0.006    0.431±0.003^a   0.333±0.004^a  2.523±0.178    3.369±0.135^a 2.984±0.118^a

100    0.232±0.006    0.412±0.006^b  0.322±0.005^ab 2.612±0.213    4.001±0.115^b 3.338±0.150^ab

200    0.236±0.007    0.390±0.010^c   0.313±0.008^b  2.925±0.291    4.759±0.328^c 3.746±0.206^b

Significant       NS                  ***                    *                    NS                ***                      *

 

Dietary supplementation:

Without 0.231±0.008 0.392±0.011^a   0.311±0.008^a  2.996±0.280    3.974±0.222 3.523±0.235

Vit. E 0.237±0.006    0.418±0.007^b  0.327±0.005^b  2.648±0.231    4.296±0.312 3.425±0.169

Calcium 0.235±0.005 0.423±0.003^b  0.329±0.003^b  2.418±0.143    3.858±0.317 3.120±0.144

Significant       NS                  ***                    *                    NS                 NS                     NS

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without 0.238±0.007 0.428±0.002^ab 0.333±0.004    2.577±0.240    3.557±0.289 3.118±0.244

Vit. E 0.236±0.011    0.438±0.006^a   0.337±0.007    2.509±0.327    3.566±0.120 3.084±0.165

Calcium 0.232±0.015 0.426±0.004^ab 0.329±0.009    2.483±0.460    2.982±0.087 2.751±0.198

100 mg lead:

Without 0.228±0.014 0.394±0.006^c   0.311±0.010    2.801±0.336    4.208±0.340 3.551±0.333

Vit. E 0.236±0.015    0.413±0.010^bc 0.325±0.012    2.748±0.583    3.961±0.066 3.362±0.321

Calcium 0.231±0.007 0.428±0.006^ab 0.330±0.006    2.288±0.120    3.833±0.038 3.101±0.074

200 mg lead:

Without 0.226±0.020 0.354±0.013^d  0.290±0.016    3.609±0.687    4.157±0.511 3.900±0.579

Vit. E 0.240±0.012    0.401±0.007^c   0.320±0.005    2.685±0.420    5.359±0.509 3.829±0.262

Calcium 0.242±0.004 0.415±0.003^bc 0.328±0.003    2.481±0.083    4.759±0.639 3.508±0.245

Significant       NS                   **                    NS                   NS                 NS                     NS

____________________________________________________________________________________

M = Month

NS = Not significantly, * P<0.005, ** P<0.01 and  *** P<0.001.

Means in the same column within each classification with different letters differ significantly (P<0.05).

 

 

Table 3. Blood heamoglobin and serum total protein and its fractions of Nile tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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Items     Hemoglobin  Total protein     Albumin         Globulin

              (g/100 ml)                   (g/100 ml)                (g/100 ml)              (g/100 ml)

___________________________________________________________________________

Lead level in diets (mg/kg diet):

0             5.000±0.170^a            5.189±0.131^a            3.467±0.095^a       1.722±0.095

100         4.300±0.095^b            4.450±0.137^b            2.912±0.105^b       1.538±0.062

200         3.589±0.155^c            3.950±0.130^c            2.373±0.101^c       1.577±0.075

Significant           ***                              ***                           ***                          NS

 

Dietary supplementation:

Without  4.100±0.157^a            4.133±0.210^a            2.616±0.157^a       1.518±0.117

Vit. E      4.194±0.290^a            4.550±0.184^b            2.906±0.189^b       1.644±0.042

Calcium  4.594±0.244^b            4.906±0.187^c            3.231±0.153^c       1.674±0.059

Significant            **                               ***                           ***                          NS

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without  4.467±0.164             4.850±0.218             3.100±0.115         1.750±0.301

Vit. E      5.133±0.101             5.200±0.173             3.567±0.093         1.633±0.093

Calcium  5.400±0.264             5.517±0.134             3.733±0.101         1.783±0.044

100 mg lead:

Without  4.100±0.115             4.033±0.060             2.660±0.156         1.373±0.116

Vit. E      4.250±0.180             4.417±0.142             2.850±0.104         1.567±0.060

Calcium  4.550±0.104             4.900±0.115             3.227±0.113         1.673±0.079

200 mg lead:

Without  3.733±0.348             3.517±0.159             2.087±0.024         1.430±0.144

Vit. E      3.200±0.173             4.033±0.044             2.300±0.076         1.733±0.044

Calcium  3.833±0.145             4.300±0.132             2.733±0.088         1.567±0.148

Significant            NS                               NS                            NS                          NS

___________________________________________________________________________

NS = Not significantly, ** P<0.01 and  *** P<0.001.

Means in the same column within each classification with different letters differ significantly (P<0.05).

 

 

Table 4. Some blood components of Nile tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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Items          Urea-N     Creatinine                 AST                   ALT

                   (mg/dl)                    (mg/dl)                           (U/l)                     (U/l)

___________________________________________________________________________

Lead level in diets (mg/kg diet):

0             2.060±0.051^a       1.101±0.022^a          41.744±1.062^a          19.944±0.174^a

100         2.416±0.057^b       1.358±0.054^b          45.922±0.190^b          21.389±0.201^b

200         2.653±0.114^c       1.594±0.071^c          49.239±1.037^c          25.392±0.734^c

Significant           ***                      ***                           ***                             ***

 

Dietary supplementation:

Without  2.608±0.128^a       1.473±0.100^a          48.130±1.285^a          23.081±1.215^a

Vit. E      2.307±0.093^b       1.352±0.085^b          45.059±1.334^b          22.083±0.806^ab

Calcium  2.214±0.075^b       1.228±0.052^c          43.717±1.123^b          21.561±0.572^b

Significant           ***                      ***                           ***                               *

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without  2.200±0.076^cd      1.137±0.059           45.167±1.940           20.183±0.404^c

Vit. E      2.020±0.089^d       1.083±0.020           40.333±0.641           19.883±0.361^c

Calcium  1.960±0.038^d       1.083±0.027           39.733±0.693           19.767±0.148^c

100 mg lead:

Without  2.580±0.085^b       1.500±0.076           46.900±0.924           21.550±0.486^c

Vit. E      2.300±0.076^c       1.357±0.081           45.600±0.794           21.300±0.416^c

Calcium  2.367±0.073^bc      1.217±0.044           45.267±0.808           21.317±0.232^c

200 mg lead:

Without  3.043±0.074^a       1.783±0.073           52.323±1.116           27.510±1.459^a

Vit. E      2.600±0.076^b       1.617±0.088           49.243±0.497           25.067±0.555^b

Calcium  2.317±0.101^c       1.383±0.088           46.150±1.381           23.600±0.361^b

Significant             *                         NS                          NS                                  *

________________________________________________________________________________

NS = Not significantly, * P<0.05 and  *** P<0.001.

Means in the same column within each classification with different letters differ significantly (P<0.05).

 

Table 5. The body composition and lead residue of Nile tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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Items   Moisture    Protein¹ Ether extract¹    Ash¹             Lead residue²

___________________________________________________________________________

Lead level in diets (mg/kg diet):

0          71.91±0.38^a     59.13±0.59^a       15.22±0.38^a       25.64±0.26      0.0022±0.0004^a

100      71.36±0.48^a     59.23±0.32^a       14.62±0.25^ab     26.14±0.23      6.9200±0.5596^b

200      70.02±0.24^b    60.77±0.61^b       13.82±0.44^b      25.41±0.23    15.8111±0.9042^c

Significant          **                     *                     **                      NS                         ***

 

Dietary supplementation:

Without 70.79±0.57^a    60.87±0.67^a       13.60±0.46^a       25.53±0.31      8.8542±2.6635^a

Vit. E   71.27±0.40^a     59.43±0.40^b       14.87±0.28^b      25.70±0.23      7.3119±2.3631^b

Calcium 71.22±0.41^a    58.83±0.39^b       15.20±0.24^b      25.97±0.22      6.5672±1.9527^b

Significant         NS                    *                     **                      NS                          **

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without 72.65±0.80      59.80±1.35        14.70±0.82        25.50±0.59      0.0023±0.0009

Vit. E   71.68±0.46      58.83±0.79        15.60±0.60        25.57±0.43      0.0023±0.0009

Calcium 71.40±0.67     58.77±1.18        15.37±0.70        25.87±0.50      0.0017±0.0007

100 mg lead:

Without 70.30±0.53      59.93±0.49        13.80±0.17        26.27±0.49      8.4933±1.1644

Vit. E   71.93±0.88      58.90±0.46        14.77±0.24        26.33±0.26      5.9667±0.4631

Calcium 71.83±0.94     58.87±0.65        15.30±0.29        25.83±0.50      6.3000±0.5508

200 mg lead:

Without 69.43±0.39      62.88±0.54        12.30±0.62        24.82±0.13    18.0667±1.4495

Vit. E   70.20±0.23      60.57±0.41        14.23±0.20        25.20±0.21    15.9667±1.3113

Calcium 70.43±0.44     58.87±0.07        14.93±0.20        26.20±0.21    13.4000±0.7234

Significant         NS                   NS                   NS                     NS                          NS

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1 On dry matter bases. 2 ppm on dry matter bases

NS = Not significantly, * P<0.05, ** P<0.01 and *** P<0.001.

Means in the same column within each classification with different letters differ significantly (P<0.05).

 

 

Table 6. Rate of mortality of tilapia fish as affected by dietary lead contamination and vitamin E and calcium supplementation and their interaction.

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Items        M1             M2               M3               M4            Total

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Lead level in diets (mg/kg diet):

0                      3                      1                        2                        2                        8

100                  3                      4                        5                        6                      18

200                  4                      5                        6                        7                      22

 

Dietary supplementation:

Without            4                      4                        8                        7                      23

Vit. E               3                      3                        3                        5                      14

Calcium           3                      3                        2                        3                      11

 

Interaction between dietary lead levels and dietary supplementation:

0 mg lead:

Without            1                      0                        1                        1                        3

Vit. E               1                      1                        1                        0                        3

Calcium           1                      0                        0                        1                        2

100 mg lead:

Without            1                      2                        3                        3                        9

Vit. E               1                      1                        1                        2                        5

Calcium           1                      1                        1                        1                        4

200 mg lead:

Without            2                      2                        4                        3                      11

Vit. E               1                      1                        1                        3                        6

Calcium           1                      2                        1                        1                        5

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M = Month.