Effects of Dietary Fish Oil Levels on Growth Performance and Nutrient Utilization in Larval Glass Catfish, Kryptopterus lais (Bleeker, 1851)

Abstract

The glass catfish, Kryptopterus lais (Bleeker, 1851), is economically important; however, its larval nutritional requirements remain poorly understood. This study evaluated the effects of dietary lipid levels on growth, feed utilization, survival, and whole-body composition of K. lais larvae. Eleven-day-old post-hatchlings with an initial body weight of 0.01±0.00 g and total length of 0.47±0.01 cm were reared for 60 days in net cages at 50 fish per cage, with three replicates per treatment. Four isoproteic diets containing 42.86% crude protein and 5%, 10%, 15%, or 20% lipid were compared with a commercial diet. Larvae were fed to apparent satiation four times daily. Growth performance and feed utilization improved as dietary lipid increased to 15%, whereas the 20% lipid diet provided no additional benefit. Survival exceeded 96% in all treatments and was not significantly affected by treatment. Second-order polynomial regression estimated optimal dietary lipid levels of 14.40 based on specific growth rate and 15.36% based on feed conversion ratio. Whole-body crude protein was highest in fish fed the 15% lipid diet and was comparable to that of fish fed the commercial diet. Whole-body lipid content was higher in fish fed 15%, 20%, and commercial diets than in those fed the 5% and 10% lipid diets, whereas moisture and ash were unaffected. In conclusion, these findings indicate that approximately 15% dietary supports favorable growth performance and feed utilization in K. lais larvae. Further studies using isoenergetic diets are needed to confirm the dietary lipid requirement of this species.