Evaluation of a modified feeding strategy on the growth, metabolism and feeding economics of Snubnose Pompano Trachinotus blochii (Lacepede, 1801) in a recirculatory system

An experiment was conducted for 60 days to evaluate the performance of modified feeding strategy through alternate level of dietary protein in snubnose pompano, Trachinotus blochii for better nutrient utilization and to reduce feed wastage. The juveniles of snubnose pompano with an average weight of 3.0 ± 0.2 g were distributed in 12 numbers of tanks in a re-circulatory system. Four iso-caloric diets with varying level of crude protein viz., 400, 350, 300 and 250 g/kg were made and designated as P400, P350, P300 and P250. Four treatments each with triplicates were maintained based on four different feeding schedules such as regular feeding of P400 (P400/400), alternate feeding of one day P400 - next day P350 (P400/350), alternate feeding of one day P400- next day P300 (P400/300) and alternate feeding of one day P400- next day P250 (P400/250). The results showed a significant difference (P < 0.05) in specific growth rate (SGR), growth rate on metabolic body weight (GRMBW), daily growth co-efficient (DGC) and thermal growth co-efficient (TGC) among the treatments and relatively higher in treatment P400/350 followed by P400/400 and P400/300. The protein efficiency ratio (PER) and protein productive value (PPV) were higher in P400/350 treatment and lowest in P400/250. The whole body crude protein and lipid contents were found higher in P400/350 and P400/400 treatments respectively. The body indices of fish showed an increasing trend with decreased protein diet on alternate days and the maximum value was witnessed in P400/250 treatment. Higher level of serum total protein and triglycerides were recorded in P400/400 and P400/250 treatments respectively. The protease and α-amylase activities were higher in P400/350 and P400/250 treatments respectively. There was significant difference (P < 0.05) in alkaline phosphatase (ALP), acid phosphatase (ACP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities among the treatments and showed a decreasing trend as the protein content of diet decreased in the fish fed with lower dietary protein on alternate days. Reverse trend was observed in lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) enzyme activities. The P400/350 feeding schedule registered a relative feed cost savings of 4.49% in comparison with P400/400 group. The present study revealed better growth performance, protein utilization and lower feed cost in the fish of treatment P400/350, which was associated with balanced digestive and metabolic enzyme activities achieved through alternate level of higher and lower protein diet feeding