Quantifying the dietary potassium requirement of juvenile grass carp (Ctenopharyngodon idellus)

Abstract

A growth trial lasting for 12 weeks was conducted in a semi flow-through system to determine the dietary potassium requirement of juvenile grass carp (Ctenopharyngodon idellus) with an initial body weight of 4.8 g. Seven isonitrogenous and isoenergetic semi-purified diets were compounded with different dietary potassium levels: 1. 50, 2.32, 3.28, 5.30, 7.12, 9.45 and 10.44 g kg −1 diet. The results showed that specific growth rate and feed efficiency of grass carp were significantly (P b 0.05) affected by dietary potassium level, the highest value of specific growth rate was in 5.30 g kg −1 group and feed efficiency values in 5.30, 7.12 and 9.45 g kg −1 groups were significantly higher than those in the other groups. The survival rate of grass carp in the present study was not affected by dietary potassium level (P N 0.05). The Na + -K + ATPase activity value in the gills varied significantly (P b 0.05) with dietary potassium level and showed an increasing and then decreasing trend, and the highest value was in the 7.12 g kg −1 group. Dietary potassium level showed significant (P b 0.05) effect on serum SOD, ALP and AST activities. SOD and ALP activities increased and then decreased as potassium level increased, while AST decreased first and then increased. Serum TP and TC contents increased and then decreased with potassium level (P b 0.05). TG, ALT and BUN were not affected by dietary potassium level (P N 0.05). Body potassium and moisture contents increased and lipid content decreased with dietary potassium content, while ash content in fish body increased first and then decreased as potassium content increased (P b 0.05). Body protein in the 10.44 g kg −1 group was significantly lowered (P b 0.05). However, calcium, magnesium, phosphorus and sodium contents in dry matter were not affected by dietary potassium level. When the potassium content of water was 1.86-3.10 mg L −1 , judging from the polynomial regression analysis for the specific growth rate of fish and the Na + -K + ATPase activity in the gill, and the broken-line analysis for body potassium content, the optimal dietary potassium content for juvenile grass carp was 4.65, 7.27 and 5.98 g kg −1 diet respectively.

Dietary potassium requirement of fingerling Indian major carp,Labeo rohita(Hamilton), based on growth parameters, gill Na+-K+ATPase activity, tissue mineralization and antioxidant activities

“…In this study, fish fed basal diet (K 1 ) exhibited deficiency signs such as poor growth, decrease in gill Na + ‐K + ATPase activity and reduced potassium deposition in the whole‐body, vertebrae and scales (Tables –). Similar potassium deficiency signs were also reported in chinook salmon (reared in freshwater containing <1 mg K/L; Shearer, ), hybrid tilapia (reared in freshwater containing 1.08–3.62 mg K/L; Shiau & Hsieh, ), rainbow trout (Kalantarian et al, ) and grass carp (reared in freshwater containing 1.71–8.18 mg K/L, Liang et al, ; 1.86–3.10 mg K/L, Zhu et al, ; 6.86–9.10 mg K/L, Chen et al, ).…”

“…Analysed dietary potassium concentrations of 0.32 (basal diet), 1.35, 2.41, 3.46, 6.48, 9.47 and 12.39 g/kg were found in K 1 , K 2 , K 3 , K 4 , K 5 , K 6 and K 7 , respectively. Dietary potassium levels were fixed taking into consideration the requirements reported for grass carp (Chen et al, ; Liang et al, ; Zhu et al, ). Vitamin‐free casein and gelatin were used as dietary protein sources and dextrin as carbohydrate source to achieve the desired level of energy in experimental diets.…”

“…It is required by a variety of enzymes to act in the carbohydrate metabolism, protein synthesis, nutrient transport and phosphorous metabolic reactions (Black, ; Chen et al, ; Luft, ). Furthermore, it has been reported that inclusion of an optimal dietary potassium level enhanced the antioxidant response in fish (Chen et al, ; Zhu et al, ).…”

“…Essentiality of potassium for maintaining normal growth and physiological activities of fish has been clearly demonstrated (Chen et al, ; NRC, ). Dietary deficiency of potassium in fish results in stunted growth and protein utilization, anorexia, seizures, convulsions and death, whereas excess dietary potassium intake also depresses fish growth (Shearer, ; Shiau & Hsieh, ; Zhu et al, ). Dietary potassium requirements have been quantified for a very limited number of aquaculture fish species such as chinook salmon, Oncorhynchus tshawytscha (Shearer, ); channel catfish, Ictalurus punctatus (Wilson & El Naggar, ); hybrid tilapia, Oreochromis niloticus × O. aureus (Shiau & Hsieh, ); rainbow trout, O. mykiss (Kalantarian, Rafiee, Farhangi, & Mojazi Amiri, ); and grass carp, Ctenopharyngodon idella (Chen et al, ; Liang et al, ; Zhu et al, ).…”

Fortification of an Aquafeed with Potassium Chloride Does Not Improve Survival of Juvenile Australian Snapper Pagrus auratus Reared in Potassium Deficient Saline Groundwater

“…Even rarer are studies considering the impacts of feeding when there is an ionic deficiency in the rearing medium. Fish reared in freshwater where [K + ] was low were shown to have some requirement for dietary K + [31,[36][37][38]. However, evidence that marine fish respond positively to dietary salts let alone dietary K + remains a point of conjecture, mostly because studies have been conducted in water bodies where [K + ] and the concentration of other ions was probably sufficient to meet their needs, e.g., [39].…”