Abstract
Two completely randomized experimental designs were conducted to investigate the effect of different levels of dietary Ca (0.95%, 1.21%, 1.41% and 1.61%) and K (0.72%, 0.9%, 1.1% and 1.3%) on some growth indices, body biochemical composition and some whole body elements in rainbow trout fingerlings in a culture system. Tow basic diets with 0.95% Ca and 0.72% K were prepared and with CaCO3 for experiment Ð and K2CO3 for experiment ÐÐ, other dietary treatments were built. In initiation of each experiments, 25 pieces of rainbow trout fingerlings (12.18 ± 0.04 and 15.60 ± 0.05) introduced in each experimental units respectively, and were fed with dietary treatment ad libitum two times daily at 9:00 and 15:00 for a 8 week period. It was resulted that different levels of inorganic dietary-Ca in diets, had not significantly affected on growth factors (W1, WG, G%, SGR% day-1 and TGC), but different levels of inorganic dietary-K in diet had significantly affected (p<0.05) on these factors. FCR and survival rates did not show significant differences between the treatments in each experiment. In The first experiment, crude protein CP% and Ash% significantly increased and total lipid showed depletion with an increase in the dietary Ca (p<0.05). Change in inorganic dietary-Ca had significantly affected on Ca, P, Mn, Zn, Cu and Fe of whole body contents (p<0.05) and not affected the Mg and K of whole body. With increasing the inorganic dietary-K, diet with 0.9% total K, had significantly increased in CP% (p<0.05), however not significant differences between the trails in Ash% and total lipid% were observed. The Ca, K, P, Mg, Zn, Fe and Cu of whole body were significantly changed (p<0.05), and Mn had not significantly changed with increasing the inorganic dietary-K. Results were obtained in these studies, showed that, changes in amount of inorganic Ca in diets at the range of 0.95- 1.61% could not significantly affect on growth indices but dietary-K at the range of 0.72-1.3% affected the growth indices significantly (p<0.05). Significant effects on biochemical composition and some whole body minerals of cultured rainbow trout fingerlings with changes the dietary Ca and K were observed.
Highlights
Minerals are required for the normal life processes, and fish, need these inorganic elements
In the present study, we investigated the effect of different levels of inorganic dietary Ca and K on some growth indices, body biochemical composition and some whole body minerals in rainbow trout fingerlings in a culture system to access the new data in the widely range
With increased the inorganic dietary-C, The differences observed in final body weight, weight gain, growth percent (G %), SGR% and TGC% were not statistically significant (P>0.05) (Table 4)
Summary
Minerals are required for the normal life processes, and fish, need these inorganic elements. Fish may derive these minerals from the diet and from ambient water [1,2,3]. All forms of aquatic animals require inorganic elements or minerals for their normal life processes [3]. Calcium is one of the most abundant cations in the body of a fish and closely related to the development and maintenance of the skeletal system and participate in several physiological processes including the maintenance of acid–base equilibrium, osmoregulation, muscle contraction, bone mineralization, blood clot formation, nerve transmission, maintenance of cell membrane integrity, and activation of several important enzymes [3,5,6] and is readily derived from the water and occurs in adequate amounts in most diets consumed by fish [3]. Teleosts possess two hormones with hypocalcemic action: calcitonin, secreted by the ultimobranchial gland, and stanniocalcin (STC), secreted by the corpuscles of Stannius [7]
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