Time-dependent dynamic alterations of flesh nutrient composition and texture quality in Nile tilapia (Oreochromis niloticus) fed on high-fat diet

High-fat diet (HFD) affects flesh quality in fish, but the dynamic changes in flesh nutritional composition and texture parameters have not been comprehensively studied. In this study, six replicates of thirty Nile tilapia ( Oreochromis niloticus ) weighing 5.5 ± 0.3 g were fed a medium-fat diet (MFD, 6 % fat) or a HFD (12 % fat) for eight weeks. The results showed that feeding the fish on HFD increased body weight and lowered feed intake than those fed on MFD. However, the fish fed on MFD had significantly higher phospholipids (PL), phosphatidyl choline (PC) and phosphatidylethanolamine (PE) contents in muscle than those fed on HFD, primarily during sixth and eighth weeks. The fish fed on HFD accumulated more n-6 polyunsaturated fatty acids (PUFAs) in muscle, meanwhile fewer n-3 PUFAs as feeding continued. The amino acids changed mainly from the sixth week, when HFD feeding generally reduced essential amino acids (EAA) and half essential amino acids (HEAA) contents in muscle. The fish fed on HFD up-regulated the genes related to enhanced fiber hypertrophy such as myogenin ( MyoG ) and myogenic factor 6 ( myf6 ) than those fed on MFD during the second and fourth weeks. Consequently, this led to reduced muscle fiber density and flesh hardness in fish fed on HFD from the sixth to eight weeks. Altogether, our study indicates that the nutritional composition and flesh texture parameters are modified during HFD feeding in Nile tilapia at different time points such that the regulation of each parameter has a distinct “time window”. • High-fat diet (HFD) reduces n-3 PUFAs and phospholipids in muscle over time. • Essential and delicious amino acids decrease in muscle during HFD feeding. • HFD reduces flesh hardness from the sixth to eight weeks. • Character changes of fish muscle exhibit distinct "time window" under HFD.