FASTING ON PHYSICAL PARAMETERS AND POSTPRANDIAL METABOLIC RESPONSE IN JUVENILE ANDRIAS DAVIDIANUS

Animals often experience different degrees of food deprivation in natural conditions, yet their adaptation strategies to starvation stress differ. In order to investigate the effects of fasting on physical parameters and postprandial metabolic response in amphibians, we selected the juvenile Andrias davidianus as experimental subjects. Forty individuals (5.44±0.08) g, (10.87±0.06) cm were randomly divided into 4 groups: a control group (F0), a 1-week fasting group (F1), a 2-week fasting group (F2), and a 4-week fasting group (F4). Subsequently, body mass, body length, rest metabolic rate (MO_2rest), and postprandial metabolic response of these animals were measured after different fasting periods. Final body length and body mass in F1, F2, and F4 groups were significantly lower than their initial measurements (P<0.05). Moreover, the final condition factor in F4 group was significantly lower than its initial condition factor (P<0.05). While there was no significant difference in final body length among the F1, F2, and F4 groups, the final body mass and condition factor in F4 group were significantly lower than those of F1 and F2 groups (P<0.05). Additionally, there was no significant difference in the rate of change in body length among the F1, F2, and F4 groups (–3.51%, –2.72%, and –2.76%, respectively). However, the rate of change in body mass (–18.54%) and condition factor (–11.30±1.50) in F4 group were significantly lower than those of F1 (–11.48% and –1.26±3.07, respectively) and F2 (–11.81% and –3.89±2.60, respectively) groups (P<0.05). There was no significant difference in MO_2rest between the F2 and F4 groups, but they were significantly lower than that in the F0 and F1 groups (P<0.05). There were no significant differences in Peak metabolic rate (MO_2peak), time to peak metabolic rate, or duration in the different treatment groups. Furthermore, the factorial metabolic scope in F4 group was significantly higher than those of F0, F1 and F2 groups (P<0.05). The energy expended on SDA and SDA coefficient in F4 group were significantly higher than those of F0 and F1 groups (P<0.05). Our results suggested that (1) the body mass of juvenile A. davidianus decreased more significantly than body length during fasting; (2) juvenile A. davidianus significantly downregulated their basic maintenance energy expenditure during 2 to 4 weeks of fasting; (3) the maximum digestive metabolism and digestive time of juvenile A. davidianus kept stable during fasting. However, fasting for 4 weeks led to a significant increase in the postprandial metabolic energy consumption, possibly due to the additional energy required for the structural and functional recovery of the digestive system after refeeding. Overall, fasting has a significant impact on the physical parameters, the basic maintenance energy expenditure and the postprandial metabolic energy consumption of juvenile A. davidianus, but its influence degree is related to the duration of fasting.