Influence of Salinity on Protein Requirements of Rainbow Trout (Salmo gairdneri) Fingerlings

Abstract

Rainbow trout (Salmo gairdneri) juveniles maintained at 10 and 20 ppt salinity were fed seven diet treatments from 30 to 60% protein in 5% increments for 10 weeks. The fish were stocked in cones, initially 50 fish per cone. Biweekly weights of diets and fish were determined and mortality was recorded daily. Percentage weight gain, gross diet efficiency, and protein efficiency ratio (P.E.R.) were computed. The minimum protein levels required for fish to achieve highest performance using these criteria were 40 and 45% for those maintained at 10 and 20 ppt, respectively. Mortality was significantly (P < 0.05) higher for fish maintained at the higher salinity. Analyses of the fish carcasses were conducted at the beginning and end of the experiment on representative samples to estimate the grams protein retained and apparent net protein utilization (N.P.U.) to verify the above findings. All the available data showed that dietary protein was of major consequence on all measurements until the minimum required level of protein in the diet was reached, while salinity was of minor consequence. P.E.R. and apparent N.P.U. were 2.10 and 34.4, respectively, for casein diets at the 40% protein level.

Effect of water temperature on dietary protein requirement, growth and body composition of Asian catfish, Clarias batrachus fry

“…3). The higher PER can be achieved at minimal dietary protein level, which was consistent with the data reviewed by Millikin (1983) in striped bass, Zeitoun et al (1973) and Yu et al (1977) in rainbow trout. In contrast to this, lower PER was reported with increasing dietary protein (Lee and Putnam, 1973;Bromley, 1980;Kim and Lall, 2001;Ng et al, 2001).…”

Optimum dietary phosphorus level of juvenile Japanese flounder Paralichthys olivaceus reared in the recirculating system

“…0.4%) of eel and channel catfish, 31,33 however, it is higher than the requirement (0.3%) for Korean rockfish 28 . anova test, the broken‐line model, and the quadratic regression analysis have been used to determine the protein requirements of several species of fish 26,34–37 . As shown in this study, similar results were obtained from all three methods.…”

Environmental effects on feed utilization

“…Best growth and feed efficiencies were noted at a salinity of 8 ppt (Jurss et ak 1985). The works of Shaw et al (1975) on the Atlantic salmon led to conclusions similar to those of Zeitoun et al (1973Zeitoun et al ( , 1974 except that at salinities above 29 ppt, the maintenance needs were increased. This salinity of 29 ppt seems to be a critical level for rainbow trout beyond which significant changes within the intracellular pools occur.…”

“…Zeitoun et al (1973Zeitoun et al ( , 1974 observed only slight differences in the protein requirements of rainbow trout and coho salmon at salinities of either 10 or 20 ppt. Lall and Bishop (1979) showed that protein and lipid utilization in rainbow trout adapted to fresh water and sea water differed and concluded that the protein requirement was higher in the latter.…”