EFFECT OF ARTIFICIAL FEEDING ON DIGESTIVE EFFICIENCY, GROWTH AND QUALITIES OF MUSCLE AND OOCYTE OF MATURING ATLANTIC MACKEREL (SCOMBER SCOMBRUS L.)

Abstract

Maturing Atlantic mackerel with and without artificial feeding, kept in sea pens (September to May), showed differences in digestive efficiency (protease activity ratio of trypsin to chymotrypsin), muscle growth (concentrations of RNA, protein, RNA/protein ratio and free amino acids [FAA]) and oocyte quality (trypsin-like specific activity, and concentrations of RNA, RNA/protein ratio and FAA). The artificially fed mackerel had higher body weights (1.7 times) but with less white muscle protein concentration (0.5 time), compared to the control group. Both groups showed higher levels of capacity for protein synthesis in the oocytes than in the white muscle, but it was about two times higher in the artificially fed fish whereas about four times higher in the control group. This indicated that, during maturation, development of oocytes and muscle for growth occurred concurrently in higher growth mackerel, while development of oocytes dominated in slower growth fish. A higher trypsin-like specific activity with higher FAA levels in the oocytes from females fed with an artificial diet, compared to the control group, suggested differences in development and quality between the gametes of the fish with different feedings. PRACTICAL APPLICATIONS The work illustrates differences in digestive efficiency and the quality of growth performance (growth and protein metabolism in muscle and oocytes) in fish with different feedings. The use of various methods for evaluating digestive efficiency and the quality of fish growth performance could provide reasonable information for some important biological differences between fish groups, especially when the number of samples are low. It is more advantageous to apply different methods simultaneously than using growth parameter alone in order to study for precise evaluation of the quality of fish growth performance. The methods are very practical for studying food utilization and growth quality of fish in different environmental conditions and with different behaviors in aquaculture as well as in natural ecosystem where food consumption rate and feeding regime cannot be under control.