Changes in the physiological parameters, fatty acid metabolism, and SCD activity and expression in juvenile GIFT tilapia (Oreochromis niloticus) reared at three different temperatures.

We evaluated the effects of rearing temperature on the composition of fatty acids and stearoyl-CoA desaturase (SCD) activity and gene expression in GIFT (genetically improved farmed tilapia) tilapia. Three triplicate groups of fish were reared for 40 days at 22, 28, or 34 °C. At the end of the trial, the final body weight of juveniles reared at 28 °C was higher than that of fish reared at 22 or 34 °C. Feed intake, feed efficiency, and the protein efficiency ratio were also higher at 28 °C. The fatty acid composition of muscle tissue differed significantly (P < 0.05) among the treatment groups. The content of SFA decreased with decreasing temperature, whereas the UFA content increased. We observed high levels of PUFA, particularly n-3 PUFAs, in fish reared at the lower temperature. Rearing at low temperature significantly (P < 0.05) increased the expression and activity of the SCD gene. Increased SCD activity and gene expression can increase the biosynthesis of MUFAs in GIFT tilapia muscle. Additionally, cold acclimation can decrease the content of TC and TG in GIFT tilapia, which can help increase cold tolerance.