Introduction:
Millions of human beings suffer due to hunger and malnutrition and fish form a rich source of food, providing a means to tide over the nutritional difficulties. In addition to proteins, fat, carbohydrate, vitamin and minerals are also required in small amount for the proper functioning of body to prevent the deficiency disease and better fish production. Fish has the ability to absorb required mineral from the surrounding water as were as from the diet. The recent year Se has received a considerable attention in animal as well as in fish nutrition. The optimum Se levels to be added in the diets may be helpful for growth, survival in the fingerlings of cirrhinus mrigala.

The water, levels of required minerals for the fishes may be poor with are necessitated either through fertilization of water or by mineral supplementation in fish diets. The latter is more practical and suitable, when fish are cultured in closed system. Those minerals essential to fulfill the nutritional requirements of higher animal, are also considered essential for fish. Fishes generally require a certain amount of mineral mixture in practical diets for optimize growth. However, response to mineral mixture supplemented in purified test diets is species specific for the fish.

Selenium is most abundant in the animal body and mainly concentrate in skeletal tissues. It is also an essential element for the fish growth. In aquatic environment fish can absorbed selenium through their gills, body surface and available food. It is established that dietary selenium increases the growth of certain fish species. The excessive waterborne selenium (100 mg 1^-1) is also reported acutely lethal to certain species of fish. Most vegetable and fruit contain 0.01 mg Se/g, and higher amount of Se are also present in other sea foods (0.3 - 0.7 mg Se/g), sea meat (0.15-2.00 mg Se/g) and grains (0.03-0.06 mg Se/g). Dietary requirements of selenium have determined for atlantic salmon (Salmo salar) Rainbow trout (Salmo gairdneri) using growth and biochemical parameters. Bell et al. 1987. The purpose of this study was to optimize the dietary requirement of selenium for the Indian Major Carp Cirrhinus mrigala fingerling. The nutritional requirements for fishes have been found to change with size, water qualities and per cent ingredients in the diet (Halver, 1972) investigated the macro and micronutrient requirement of fishes. Gatlin and Wilson (1984) suggested that growth of certain affected by dietary selenium level, and significant differences in weight grain were not easily desirable due to variability among the groups of fish. How much selenium is available from fish may have to be considered and imported when assessing selenium status of human being from the dietary intake.

Materials and methods:

The selenium as Na₂SeO₃ was used in the present study. Graded levels of selenium ranging from 0.0 to 0.64 mg/kg (Table 1.5) were added separately in the diet vermicelli (Figure 1.1)

Figure 1.1: Showing the vermicelli of practical and purified diets used in the feeding experiments.

were air dried and refrigerated. The ingredients used in the practical diet (Table 1.1). The details of vitamin and minerals premix used to the practical diet was illustrated in tables 1.2 and 1.3. The purified diet was used to determine the optimum requirement of selenium for the fingerlings of cirrhinus mrigala   in respect to growth (Table 1.1).

1.         Vitamin mixture                                  -           see table 1.2
2.         ADEK mixture                                    -           see table 1.4
3.         Selenium free mineral mixture           -           see table 1.3
4.         Selenium levels                                   -           see table 1.5

Table 1.1: Per cent ingredients of the purified diet used for Se requirement of the mrigal fingerlings.

Table 1.2: Composition of vitamin mixture used in the purified diet

Table 1.3: Composition of selenium free mineral mixture used in the purified diet.

Table 1.4:  Composition of ADEK mixture, i.e. fat-soluble vitamins used in the purified diet.

* as Na₂SeO₃
Table 1.5:  Level of selenium* tried in the feeding experiment for dietary requirement of mrigal fingerlings.

The contents were mixed thoroughly and added 10%   distilled water to prepare a thick paste. Vermicelli of diameter 1 mm size were made from the paste.

The healthy and same age groups of fingerlings were selected and acclimatized in cement cistern of 185 litre capacity for a period of 15 days (Figure 1.2).

Figure 1.2: Showing the experimental unit consisting cement cisterns of 185 lit. capacity

The experimental cisterns were labeled for selenium treatments and placed in shed to prevent algal growth from the sun light and then covered   by nylon mesh (Figure 1.3).

Figure 1.3: Providing the nutritional conditions during the feeding experiments.

The weight vermicelli was dispersed in each cistern between 8 to 9 AM. The growth parameters i.e. weight gain, specific growth rate (GR), grows conversion efficiency (GCE) and food conversion ratio (FCR) were computed for the fingerlings fed selenium supplemented purified diets.

The ration given to the fingerlings was at the rate of 2 per cent of their total body weight. To avoid metabolic wastes in cistern, water was renewed twice a week, between 2.00 to 4.00 pm by siphoning. During feeding trials water temperature was ranging between 25 to 30°C.Increase in body weight of the fingerlings in varying dietary levels of selenium was recorded fortnight, i.e. on 16^th, 31^st and 46^th day of the experiment. Before weighing, the fingerlings were kept on fasting at least for a period of 24 hours. Data were computed for growth response and feed efficiency, i.e. SGR, FCR and GCE. The growth data were statistically processed for complete randomized design (CRD) as per the prescribed standard methods (Snedcor 1967).

Results and discussion:

The weight gain of C. mrigala fingerlings fed selenium supplemented purified diets have been summarized in (Table 1.6).

* @ 2 % bwpd
Table 1.6: Weight gains of mrigal fingerlings fed on selenium (Se) supplemented purified diets for an experimental period of 45 days.

* @ 2 % bwpd
Table 1.7: Selenium supplemented purified diets offered to fingerlings for a period of 45 days.

The highest weight gain of 23 per cent of fingerlings was observed at a dietary concentration of 0.32 mg Se/kg diet. In the present study weight gains efficiency for the mrigal fingerlings in relation to dietary Se levels were 0.32 > 0.16 > 0.04 > 0.007 > 0.027 > 0.01 > 0.08 > 0.064 mg Se/kg purified diet.

SGR's of mrigal fingerlings with Se supplemented diets have been presented in (table 1.8.) The values of SGR were processed for analysis of variance (ANOVA Table 1.9).

SGR for each fortnight                                               SGR for 45 days
SEm + 0.017804                                                         SEm + 0.010279
CD (5%) 0.051                                                            CD (5%) 0.029
CD (1%) 0.067                                                            CD (1%) 0.039

Table 1.8: Specific growth rate (SGR) of fingerlings fed on selenium supplemented purified diets for a period of 45 days.

CV = 8.046
**        Significant at 1%    *          Significant at 5%
NS       Non-significant
Table 1.9: Analysis of variance (ANOVA) for SGR of mrigal fingerlings fed selenium supplemented purified diets.

The average highest values of SGR of 0.511 and 0.445 g/day of fingerlings at levels of 0.32 and 0.16 mg Se/kg diet were statistically significant at 1% levels. The significant values of SGR on these dietary Se levels is due to positive growth of mrigal fingerlings.

The gross conversion efficiency in the present study was also determined by total amount of food for each Se levels offered to fingerling (Table 1.7) and their weight increment (Table 1.5). The values of GCE for the mrigal fingerlings fed varying Se supplemented purified diet have been summarized in (table 1.10). The GCE's were also statistically analysed for the analysis of variance (ANOVA, Table 1.11).

GCE for each fortnight                                               GCE for 45 days
SEm + 0.0130                                                             SEm + 0.075
CD (5%) 0.037                                                            CD (5%) 0.021
CD (1%) 0.049                                                            CD (1%) 0.028
Table 1.10: Gross conversion efficiency (GCE) of fingerlings fed on selenium supplemented purified diets for a period of 45 days.

CV = 9.87
**        Significant at 1%  * Significant at 5%
NS       Non-significant
Table 1.11: Analysis of variance (ANOVA) for GCE of mrigal fingerlings fed selenium supplemented purified diets.

The average highest GCE values of 0.281 and 2.68 for mrigal fingerlings were observed at 0.32 and 0.16 mg Se/kg diet respectively. Statistically these GCE values were also found significant at 1% levels. Significant GCE's for these dietary Se levels is due to positive and gradual weight increments in fingerlings.

The food conversion ratio of the fingerlings fed Se supplemented diet have been presented in (table 1.12. It is concluded from the values that FCR is inversely related to the GCE, i.e. wherein fingerlings exhibited highest GCE, lower FCR was recorded. For test of significant FCR values were processed for analysis of variance (ANOVA, Table 1.13).

FCR for each fortnight                                               FCR for 45 days
SEm + 0.243                                                               SEm + 0.140
CD (5%) 0.69                                                              CD (5%) 0.40
CD (1%) 0.92                                                              CD (1%) 0.53
Table 1.12: Food Conversion ratio (FCR) of fingerlings fed on selenium supplemented purified diets for an experimental period of period of 45 days.

CV = 8.44
**        Significant at 1%        *          Significant at 5%
NS       Non-significant
Table 1.13: Analysis of variance (ANOVA) for FCR of mrigal fingerlings fed selenium supplemented purified diets
The result indicates that values of FCR are statistically significant at 1 per cent levels for the fingerlings fed on Se supplemented purified diets. The significant (1 % level) average lower FCR's of 4.03 and 4.08 for fingerlings at concentration of 0.32 and 0.02 mg Se/kg diets were measured with highest average weight gains of respectively 23 and 17 g for a period of 45 days. On the contrary other dietary Se levels, 0.00 (control), 0.01, 0.16 and 0.64 mg Se/kg diets. FCR's were also significant at 1 per cent levels. Whereas Se concentration of 0.08 mg Se/kg diet was noticed significant at 5 per cent levels for the fingerlings.
Dietary requirement for Se has been evaluated for the fingerlings of cirrhinus mrigala in relation to growth response conservation and efficiency. The mrigal fingerling were observed rapidly grow fed on a level of 0.32 mg Se/kg purified diet. On other hand low dietary levels of Se including 0.32 mg/kg diet no deficiency and toxic symptoms have been observed in mrigal fingerling, as in case of catla fingerlings, Posten et al. (1976) demonstrated the dietary essentially of Se for Atlantic Salmon fry and fingerlings and also suggested that no selenium concentrations causing toxicity for Atlantic Salmon, Hitlton et al. (1980) recommended that dietary Se concentration as low as 0.07 mg/kg dry diet, prevented Se deficiency symptom in rain bow trout fingerlings. The dietary supplemented of Se upto a level of 0.32 mg/kg diet were also found helpful for increasing the growth of Cirrhinus mrigala fingerlings. The present study also suggested than a closed water below 0.32 mg Se/litre, the diets of selenium for better growth and survival of Cirrhinus mrigala fingerlings. The supplementation of Se in diets is also beneficial for improving feed conversion efficiency in the cirrhinus mrigala fingerlings as compare to selenium deficient diets.

Dietary requirement for selenium has been evaluated for the fingerlings of Cirrhinus mrigala in relation to growth response, conversion and efficiency selenium is an essential dietary component like other mineral and trace elements for the fish. The mrigal fingerlings were observed rapidly grow fed on a level of 0.32 mg Se/kg purified diet. On other hand low dietary levels of selenium including 0.32 mg/kg diet no deficiency and toxic symptoms have been observed in mrigal fingerlings, as in case of Catla fingerlings, Posten et al. (1976) demonstrated the dietary essentiality of selenium for Atlantic Salmon fry and fingerling and also suggested that no selenium concentration causing toxicity for Atlantic Salmon. Hilton et al. (1980) recommended that dietary selenium concentration as lower 0.07 mg/kg dry diet, prevented selenium deficiency symptom in rain bow trout fingerlings. The dietary supplementation of selenium upto a level of 0.32 mg/kg diet were also found helpful for increasing the growth of Cirrhinus mrigala fingerlings. The present study also suggests than in closed water below 0.32 mg Se/litre, the diets should be supplemented with optimum level of selenium for better growth and survival of Cirrhinus mrigala fingerlings. The supplementation of selenium in diets is also beneficial for improving feed conversion efficiency in the Cirrhinus mrigala fingerlings as compare to selenium deficient diet.