RENAL FUNCTION PARAMETERS OF HEALTHY CAPTIVE AND SEMICAPTIVE AMAZONIAN MANATEES (TRICHECHUS INUNGUIS)

Evaluating renal function is essential for managing captive wild animals, particularly threatened species like the Amazonian manatee (Trichechus inunguis) in rehabilitation and prerelease programs. A series of urine diagnostic tests, such as gross appearance, semiquantitative chemical analyses, microscopic review of sediments, and quantitative analyses of urea and creatinine, were performed in 57 free-catch urine samples. On the same occasion, 52 serum samples from the same individuals were analyzed for creatine kinase activity, creatinine, blood urea nitrogen, albumin, sodium, potassium, and chloride concentrations; serum symmetric dimethylarginine (SDMA) was measured for the first time in the species. Females had higher urine creatinine concentration (21.7 ± 11.8 mg/dl) and specific gravity (1.003 ± 0.003 mg/dl) than males (11.9 ± 8.5 mg/dl and 1.001 ± 0.002 mg/dl) (P < 0.01 for both). Males presented higher urine creatinine:urea ratio than females (24.8 ± 29.2 and 20.5 ± 29.2, respectively) (P < 0.05). Urine pH was lower in manatees from the semicaptive area (7.8 ± 0.6) than in manatees under human care (8.5 ± 0.6) (P = 0.02) using the benchtop pH meter but showed no difference between areas in the dipstick reaction (P = 0.71), given its lower sensitivity and narrower range detection. Furthermore, 18 and 75% of urine samples were positive for the presence of blood and/or nitrite, respectively, in the dipstick reaction, possibly because of sample contamination. Significant correlation was observed between serum blood urea nitrogen and urine urea concentrations (P = 0.02), and between serum and urine creatinine concentrations (P = 0.01). Serum SDMA did not differ between sex or between captive and semicaptive individuals. However, it positively correlated with urine (P = 0.02) and serum creatinine (P = 0.01) demonstrating its potential as a bioindicator of kidney function. The renal function of Amazonian manatees can be effectively assessed by urinalysis, especially when combined with serum biochemistry.