Effect of dietary lipid levels on the growth, feed utilization, body composition and blood characteristics of tiger puffer Takifugu rubripes

The objective of this study was to examine the effect of dietary lipid level on the growth, feed utilization, body composition, and blood characteristics of tiger puffer Takifugu rubripes. Triplicate groups of 10 g initial body weight fish were fed five isonitrogenous experimental diets formulated with increasing lipid levels (5.9, 11.0, 16.3, 21.4 and 25.7%) using pollack liver oil, twice daily to apparent satiation, 6 days per week for 8 weeks (trial 1). Survival during the 8-week rearing period ranged from 76.7 to 96.7% and survival of fish fed the 5.9% lipid diet was significantly lower than for fish fed 16.3% lipid. Weight gain and specific growth rate (SGR) were significantly greater for fish fed diets with 5.9, 11.0 and 16.3% lipid compared to other treatments. Feed efficiency and protein efficiency ratio (PER) increased with increasing dietary lipid level up to 16.3%, and decreased slightly thereafter. Similar trends were observed for blood triglyceride, hematocrit value, and hepatosomatic index of the cultured fish. Hemoglobin decreased but glucose increased with increasing lipid level and other parameters were independent of dietary composition. Proximate composition of dorsal muscle and liver was not clearly related to dietary composition. After 8 weeks rearing, fish were randomly divided into duplicate groups per dietary treatment and reared for 16 weeks as described above (trial 2). Weight gain and SGR were the highest in fish fed the 5.9% lipid diet and tended to decrease with increasing level of dietary lipid although initial body weight was lower for the higher lipid groups. On the other hand, feed efficiency and PER values for fish fed the 5.9% lipid diet were significantly lower than for fish fed the other diets. Increasing dietary lipid improved feed utilization significantly without serious effects on fish growth and health condition when it was less than 11%.