Optimization of the protein requirement of Channa striata larvae fed graded levels of protein diet

The aim of the present study was to evaluate the optimal dietary protein level and its effect on the survival rate, observed mortality, cannibalism rate, growth performance, and digestive and metabolic enzyme activity of Channa striata larvae. A total of 4,950 larvae with an average initial weight of 1.5 ± 0.00 mg and an average total length of 0.6 ± 0.01 cm were stocked at 550 larvae in triplicate and fed with isolipidic diets containing graded levels of crude protein 40% (P40), 50% (P50), and 60% (P60) for 26 days. The growth indices, including weight gain, weight gain percentage, average daily growth, protein efficiency ratio, and feed conversion ratio, exhibited a better growth performance in P50, showing a significant difference among treatments (p < 0.05). A better survival rate was observed in P50, whereas a reduced mortality and cannibalism rate was observed in P50 compared with P40 and P60. Results showed that the optimal dietary protein level of C. striata larvae based on second-order polynomial regression equation was ~51%. Digestive enzymes (amylase, lipase, total protease, trypsin, and chymotrypsin) and metabolic enzymes (alanine aminotransferase and aspartate aminotransferase) showed a similar trend, an elevated peak in P40, followed by P50 and P60. Based on the findings from the present study, it is concluded that crude protein at 51% level is optimal for better growth performance and survival of C. striata larvae.