Abstract

The eastern spiny softshell turtle (SST: Apalone spinifera spinifera), which has been listed as endangered within its range in Canada and since 2014, has been the focus of a head-start program aimed at increasing the juvenile survival rate over their first winter. From 2017 to 2020, shell deformities have been observed among the SSTs in this program, raising concerns about the potential underlying risk factors for musculoskeletal disease, including vitamin deficiencies. This study aimed to assess the impact of dietary vitamin D₃ (cholecalciferol) levels on shell deformities in captive-raised juvenile SSTs. Twenty-two juvenile SSTs from four distinct nests were selected and divided into two groups. Both groups experienced identical environmental conditions, while their diets differed only in vitamin D₃ content: the control group received standard dietary levels (‘Low’: LVD) at 1,980 IU/kg/ration and the other received an added dietary supplementation (‘High’: HVD) at 6,000 IU/kg/ration. Morphometric measurements and shell deformity severity assessments were conducted at two-week and 12-week intervals, respectively, over the course of one year. The HVD group exhibited significantly greater increases in body weight (P < 0.001) and carapace width (P = 0.004) than the LVD group by the conclusion of the study. Specifically, HVD females gained the highest body weight (P = 0.001) with LVD males displaying the lowest weight gains. Shell deformities were more prominent in females (P = 0.043) but were not different between the treatment groups. While these findings suggest a role for oral vitamin D₃ in the growth and development of juvenile SSTs, it appears that the occurrence of shell deformities in these turtles is more closely associated with sex and growth rate, rather than oral vitamin D₃ supplementation. Further investigations are warranted to comprehensively understand the nutritional needs and potential risk factors influencing shell deformity development in this endangered species.