Bioenergetics, amino acid absorption and in vivo protein biosynthesis in a siluroid fish, clarias batrachus (linn.)

A three months experimental trial was conducted with variable percentage levels of protein (25, 30, 35, 40, 45 & 50) diet fed to the common Indian catfish, Clarias batrachus to study the satiation time, maximum feed intake in different hours of the day, protein/dietary energy requirement for optimum growth in different size groups, amino acid absorption and quantitative requirement, in vivo protein biosynthesis etc. and finally to calculate the requirement of digestible energy for the production of one gram fish to thousand gram in weight. It was observed that the maximum feed intake recorded with smaller size groups (5.0 g) as compared to 20.0 g and 50.0 g, satiated within one hour and highest appetite was recorded at 18.00 hours of the day. Maximum growth were observed with 45.0% protein (5.0 ± 0.3g) followed by 40% (20.0 ± 2.1 g) and 35% (50.0 ± 3.6 g) in Clarias batrachus, although growth continued till 50% of dietary protein but not significant at the 0.5% level. Maximum weight increase recorded with 1: 14.85 digestible energy / digestible protein ratio. Maximum amino acid absorption takes place in the posterior serosal layer of the intestine. It was also recorded that the same 10 amino acids are essential and their requirement was almost at par with the other fish species, and as in higher vertebrates. However, the importance of cystine and tyrosine for the growth of Clarias batrachus should not be ignored and should be considered as two additional essential amino acids. The protein biosynthesis in vivo is highly correlated with the dietary protein/energy, feed intake and growth performance of fish.