Effects of Different Substrates on Growth, Serum Biochemical Parameters, and Behavioral Characteristics of Juvenile Asian Giant Softshell Turtles, Pelochelys cantorii

The critically endangered Asian giant softshell turtle (Pelochelys cantorii) is a national first-class protected aquatic animal in China, and artificial breeding is vital for its conservation. Given the pivotal role of substrate in captive rearing, this study aimed to investigate the effects of different substrate types on the growth, serum biochemistry, and behavior of juvenile P. cantorii. A total of 45 8-month-old juveniles [(121.11 ± 0.65) g] were randomly allocated to three groups (fine sand [FS], pea gravel [PG], and no substrate [NS]) for an 18-day rearing trial. Results indicated that the FS and PG groups exhibited significantly higher weight gain and specific growth rates than the NS group (p < 0.01). Serum malondialdehyde (MDA) levels were lower in the FS and PG groups than in the NS group (p < 0.05), with no significant difference between FS and PG. Notably, three individuals in the NS group exhibited symptoms of skin ulceration. No significant intergroup differences were observed in glucose (GLU), triglyceride (TG), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), or cortisol (CORT) levels (p > 0.05). Behaviorally, the FS group demonstrated the highest hidden rest frequency and duration (p < 0.01) and significantly lower active avoidance behavior compared to PG and NS (p < 0.01). In conclusion, substrate type significantly influences captive juvenile P. cantorii, with fine sand being optimal as it enhances growth, alleviates oxidative stress, and reduces maladaptive behaviors.