Low temperature alleviated the adverse effects of simulated transport stress on the intestinal health in Chinese soft-shelled turtle Pelodiscus sinensis

Transport stress always poses a threat to aquatic animals. Transportation under low temperatures was often used to relieve transport stress in practical production of Chinese soft-shelled turtle Pelodiscus sinensis, but their effect on the turtle's intestinal barrier remains unclear. In this study, P. sinensis (initial weight 200 ± 20 g) were exposed to simulated transport stress for 12 h at control (30 °C) and low (20 °C) temperature, and then recovery for 24 h, and each treatment had 4 replicates with each replicate containing 4 turtles. The results showed that transportation induced obvious morphological and histological damages in intestinal villus, with a down-regulated expression of the tight junction related genes. Besides turtles in transport group showed an oxidative stress in intestine, which stimulated a physiological detoxification response together with apoptosis. Low temperature transport plays a mitigative effect on the transport stress of turtle intestine via relieved stress response. Specifically, the intestinal villus/crypt (V/C) ratio and the expression of tight junction genes in the low-temperature group were significantly higher compared to the control temperature group, while stress response parameters such as intestinal cortisol levels and hsp expression were significantly lower in the low-temperature group. Additionally, low temperature alleviated oxidative damage and apoptosis caused by transport stress relative to the control temperature group. However, the protective effect of low temperature on P. sinensis intestine was limited, especially after the temperature recovery stage. Overall, the findings of the present study demonstrated that transport stress would induce the disruption of intestinal integrity and oxidative damage, also activated the mucosal immunity and antioxidant enzyme system response of turtles. It was also suggested that low temperature could alleviate the adverse effects of transport stress on intestinal integrity through modulation of oxidative status and apoptosis, whereas much less impact after temperature recovery.