SummaryThis investigation was directed towards finding the need of vitamin D for fish. The freshwater column feeder fish Labeo rohita (Rora) was used for the study. Early fry stage fish were divided into four experimental groups of 350 each: two groups were kept in natural light, while the other two were maintained under total darkness. One each of the light and dark-grown groups was supplied dietary vitamin D3 [1,650 i.u/kg diet], whereas the other groups were fed a vitamin D-deficient diet for six months. The known vitamin D-related functions and growth parameters were studied in these four experimental groups of fish. The results showed that fish reared on vitamin D-deficient diet and in dark did not have even traces of liver vitamin D, indicating a state of vitamin D deficiency in these fish. No significant differences were observed in percent bone to body weight or dry matter of the vitamin D-deficient/ supplemented groups of fish grown in light/dark. Further, it was also observed that there were no significant changes in bone and carcass ash or calcium and phosphorus content in response to vitamin D3 sup plementation as compared to the groups which did not receive vitamin D3 (grown both in light and dark). Also, there was little change in several other parameters like carcass protein and lipid, mortality rates, hepatosomatic index, and feed efficiency between the vitamin D-deficient/ supplemented groups of fish. Thus, these findings suggest that vitamin D may not be an essential nutrient for Rora (Labeo rohita) as a representa tive of freshwater fish.

The present investigation was directed towards finding the relative biopotency of vitamin D3 and D2 in fish. The freshwater column feeder fish Labeo rohita (Rora) was used for the study. The feeding of Rora with graded levels of vitamin D2 (550, 1,100 and 1,650i.u./kg diet) and vitamin D3 (1,100 and 1,650i.u./kg diet) resulted in no behavioural or morphological changes in comparison with the group fed a vitamin D-deficient diet. Also, the growth rate, feed efficiency, mortality rate, carcass protein, total lipids, calcium and phosphorus were found to remain unaltered in the vitamin D-deficient fish and fish fed any form of the vitamin. Further, there is no difference in any of the above parameters between the different doses of vitamin D3 or vitamin D2. Thus, the results of this study indicate that both of the forms of vitamin D (D2 or D3) are not biologically active for Rora (Labeo rohita) as a representative of freshwater fish.