| The objective of the present trials was to study effects of varying levels of potassium (K~+) supplementation to the low salinity waters or diets on growth, nitrogen metabolism, osmoregulation and immunity of juvenile shrimp, Litopenaeus vannamei (L. vannamei). The current studies include the followings : (1) Effects of varying levels of aqueous potassium on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei, reared in low salinity sea-waters (salinity=4). (2) Effects of varying levels of aqueous potassium on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei, reared in low salinity well-waters (salinity=4). (3) The interaction of aqueous and dietary potassium levels on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei, reared in low salinity well-waters (salinity=4). The results were surnmarized as follows:1. A 8-weeks growth trial was conducted to evaluate the effects of different aqueous K~+ levels (0, 10, 20, 40, and 80 mg/L, respectively) on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei reared in low salinity sea-waters (salinity=4). Juvenile L. vannamei with an average initial body weight of 0.23±0.01g were reared in the fiberglass tanks (350L) with five treatments low salinity sea-waters with different K~+ levels (K0, K10, K20, K40, and K80 treatment, respectively). The experiment consisted of five treatments with three replicate tanks per treatment, and each tank was stored with 40 larvaes. Shrimp were offered a experimental diet (40% crude protein, 9% crude lipid) with fish meal, soybean meal and peanut meal as the source of protein.Results of the growth trial indicated significant differences in growth among treatments (P<0.05). weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) appeared to a peak with increasing K~+ concentration, K40 treatment of shrimp yielded the highest WGR among all treatments; K10, K20 and K40 treatment of SGR were significantly higher than K0 treatment. Significant differences in oxygen consumption, ammonia-N excretion and arginase specific activity were observed in the 8-weeks growth trial in low sea-waters with various levels of K~+ (P<0.05). The oxygen consumption of K40 and K80 treatment were significantly the higher than all other treatments; K40 treatment had significantly lower ammonia-N excretion when compared to K0 and K80 treatment. Hemolymph osmolality, K~+, Na~+ and Cl- content, Na~+-K~+-ATPase activity in the gill were significant differences among treatments, and appeared to increase with increasing K~+ levels, but a opposite effect was observed for the hemocyanin content. THC, O2- content, PC, ALP, PO and SOD activity were significantly difference among treatments (P<0.05), and there were a peak with increasing K~+ levels. The results suggested that aqueous K~+ could enhance the growth and immunity when the aqueous K~+ levels is supplemented with 10~40 mg/L (total K~+ 70~110 mg/L). Consequently, when aqueous K~+ should be maintained at adequate levels, the growth of L. vannamei will be better in low salinity sea-waters.2. A 8-weeks growth trial was conducted to evaluate the effects of different aqueous K~+ levels (0, 10, 20, 40, 60, and 80 mg/L, respectively) on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei reared in low salinity reconstituted well-waters (salinity=4). Juvenile L. vannamei with an average initial body weight of 0.22±0.02g were reared in the fiberglass tanks (350L) with six treatments low salinity well-waters with different K~+ levels (K0, K10, K20, K40, K60, and K80 treatment, respectively). The experiment consisted of six treatments with three replicate tanks per treatment, and each tank was stored with 40 larvaes. Shrimp were offered a experimental diet (40% crude protein, 9% crude lipid) with fish meal, soybean meal and peanut meal as the source of protein.Results of the 8-weeks growth trial indicated significant differences among treatments (P<0.05), WGR, SGR and survival rate appeared to a peak with increasing K~+ levels, but feed conversion efficiency (FCR) revealed the reverse trend. L. vannamei can ensure better growth in the K40 treatment than K0 treatment. The oxygen consumption, ammonia-N excretion, arginase specific activity, urea and uric acid content of hemolymph were significantly differences among treatments (P<0.05), The oxygen consumption and ammonia-N excretion of K40 treatment were significantly lower when compared to K0 and K80 treatment (P<0.05); K40 treatment of urea content was significantly lower than K80 treatment; arginase specific activity of K40 and K60 treatment were lower than all other treatments and was significantly different from the K80 treatment (P<0.05). Meanwhile, hemolymph K~+, hemocyanin content and Na~+-K~+-ATPase activity in the gill were significantly differences among treatments (P<0.05), and hemolymph K~+ appeared to increase with increasing aqueous K~+ levels, but a opposite effect was observed for the hemocyanin content. In addition, Na~+-K~+-ATPase activity was highest among treatments when K60 treatment. THC, O2- content, ALP, LSZ and PO activity had a significant peak change with increasing aqueous K~+ levels (P<0.05). However, SOD activity appeared to increase with increasing aqueous K~+ levels. The present study were observed that the optimum supplementation of aqueous K~+ was 20~60 mg/L (total K~+ 56~107 mg/L) of L. vannamei reared in low salinity well-waters. The results suggested a correlation between aqueous K~+ levels and the growth, survival and immunity of L. vannamei, K~+ should be maintained at adequate levels to ensure optimum growth.3. A two-factorial experiment was conducted to determine the effeets of aqueous K~+ levels and dietary K~+ levels on growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei reared in low salinity reconstituted well-waters (salinity=4) were evaluated. Juvenile L. vannamei with an average initial body weight of 0.28±0.01g were reared in the fiberglass tanks (350L) with three different K~+ levels (10, 20, and 40 mg/L, respectively); Shrimp were offered three experimental diets (40% crude protein, 8.5% crude lipid) with three different K~+ levels (0.0, 0.3, and 0.6%, respectively) in the 8-weeks growth trial, respectively. The experiment consisted of nine treatments with three replicate tanks per treatment, each tank was stored 40 larvaes.The results showed that there were signifieant interaction between aqueous K~+ level and dietary K~+ level on the WGR, PER, FCR, hemolymph Cl- content, O2- content, ALP, LSZ, and arginase specific activity (P<0.01). When the supplementation of aqueous and dietary K~+ were 10 mg/L and 0.6%, respectively, L. vannamei showed better growth and arginase specific activity was lower than all other treatments; Hemolymph Cl- content appeared a peak with increasing dietary K~+ concentration, the supplementation of aqueous and dietary K~+ were 10 or 20 mg/L and 0.3% treatments respectively of hemolymph Na~+ and Cl- content had a highest from all other treatments. Significant differences in LSZ activity were observed in diets with various levels of K~+, and LSZ activity was the highest among all treatments when the supplementation of aqueous and dietary K~+ were 40 mg/L and 0.3%, respectively; However, the supplementation of aqueous and dietary K~+ were 10 mg/L and 0.6%, respectively, O2- content was the higher than all other treatments. In summary, the interaction between aqueous and dietary K~+ levels had signifieant effect on the growth, nitrogen metabolism, osmoregulation and immunity of L. vannamei in low salinity well-waters, the present study were observed that the optimum supplementation of aqueous K~+ was 10 mg/L (total K~+ 45 mg/L) and dietary K~+ was 0.6% (total K~+ 1.93%), or aqueous K~+ was 20 and 40 mg/L, respectively (total K~+ 56 and 81 mg/L, respectively) and dietary K~+ was 0.3% (total K~+ 1.60%), K~+ should be maintained at adequate levels to ensure optimum growth and immunity response of L. vannamei and might provide an osmoregulatory advantage. Meanwhile, these results indicated that dietary supplementation of K~+ had positively effect on improving growth of the shrimp while aqueous K~+ was not sufficient in low salinity well-waters. There was significant interactions between aqueous K~+ level and dietary K~+ level on growth, nitrogen metabolism, osmoregulation and immunity of juvenile L. vannamei were found... |
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