Effects of Low Temperature Stress on Fatty Acid Composition and Content of Oreochromis Hornorum
|School||Guangdong Ocean University|
|Keywords||Oreochromis hornorum low temperature stress fatty acid composition and content|
In the present study, the effects of low temperature stress on muscle composition, fatty acid compositon and content in various tissues of Oreochromis hornorum with different fatness were investigated, and the results are as follows:1 Effects of low temperature stress under sluggish decreasing temperatureA 50-day stress trial was conducted in indoor recirculating aquaculture system to investigate the effects of different low-temperature (25℃, 20℃, 18℃, 16℃, and 14℃) on muscle composition, morphology index, fatty acid composition and content of Oreochromis hornorum. The results showed that:Hepatosomatic index, viscerasomatic index and fatness significantly declined with sampling time extended.Moisture content significantly increased, crude fatty significantly decreased with low temperature treating time prolonging.Fatty acid composition and content of two fish groups (with significantly different fatness) in different tissues were significantly different, while the difference of fatty composion in the same tissues between the two groups were slight. In the muscle tissues of high fatness group, there are more saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), and less polyunsaturated fatty acids (PUFA). The main polyunsaturated fatty acids were linolenic acid, arachidonic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the relative amount of these acids changed significantly among tissues, especially, DHA content varied from 3.21 to 10.42. There are significant difference in∑n-3/∑n-6 ratios also among different tissues, and the ratios were 3.09 in adipose tissue, 2.54 in intestine tissues, 1.66 in liver tissues and 1.25 in muscle tissues, respectively. The highest amount of MUFA and PUFA were found in the muscle tissues, while the highest amount of SFA was found in the intestine tissues. The contents of SFA were 41.72±4.69%, 39.38±6.58%, 45.83±5.72%, 32.51±1.81%, MUFA were 17.65±4.84%, 29.77±6.49%, 27.49±2.97%, 37.89±4.69% and PUMA were 30.45±5.20%, 22.99±4.05%, 17.42±2.94%, 20.14±2.89% in muscle, liver, intestine and adipose tissues, respectively.With the extension of sampling time, the content of SFA and MUFA of muscle and fatty tissue decreased, while the content of PUFA increased in the two fish groups. At the same time, the content of SFA and MUFA in high-fatness group and the content of SFA and MUFA in low-fatness group decreased.2 Effects of low temperature stress through rapidly decreasing temperatureTransferred fish cultured at 25℃into tanks at 16℃and 13℃rapidly, and sampled each control groups (25℃) and experimental groups at 0h, 6h, 12h, 24h and 48h after the transfer. The results indicated that no significant difference was found in morphological parameters,muscle composition and fatty acid composition during the experiment. No uniform law in the fatty acid content of the tissues was found, while the greatest change of fatty acid content happened in liver tissues. By comparision with the high-fatness fish, the low-fatness fish were more adaptive to the low temperature stress through rapidly decreasing temperature.