Effects of Freeze-Thaw Cycle on Urine Values from Bottlenose Dolphins (Tursiops truncatus)

Abstract

Urinalysis is a valuable tool for assessing the renal health of marine mammals. While retrospective and population renal health studies often use frozen urine samples, it has not been determined if the freeze-thaw process alters urine values from bottlenose dolphins (Tursiops truncatus). The primary objective of our study was to compare the values of 38 fresh and frozen paired urine samples collected from 20 bottlenose dolphins at the U.S. Navy Marine Mammal Program. Paired t-tests and chi-squared tests were conducted to assess the effects of storage at -80° C for 2 to 301 d, and a subsequent thaw on urine specific gravity; pH; creatinine; protein:creatinine ratio; quantitative protein; uric acid; uric acid:creatinine ratio; and categorical characterizations of color, clarity, glucose, ketones, occult blood, protein levels, and crystals. The freeze-thaw cycle decreased urinary pH and increased urinary uric acid (p = 0.04 and 0.02, respectively). There were no other significant changes in urine variable values, including urinary uric acid concentration by grams of creatinine, when comparing fresh and frozen-thawed urine samples. Urinary uric acid concentration by grams of creatinine is the most accurate uric acid measurement when frozen-thawed samples are used. Urinary pH should be measured in fresh samples to avoid falsely decreased pH.

Validity of Urine Color Scoring Using Different Light Conditions and Scoring Techniques to Assess Urine Concentration

“…The goal of aim (c), comparing the results of frozen vs. originally scored fresh outcomes, was to generalize the results of this study to freshly scored urine samples. It is known that freezing tends to result in 0.5-0.6 (with 95% CI ranging between 0.3-0.8) darker Uc color 25 , potentially as a result of the "freezethaw" method 26 , similar to what was reported in this study. At the same time we noticed sedimentation 25 , which dissolved while slowly inverting the tubes.…”

Baseline urinalysis values in common bottlenose dolphins under human care in the Caribbean

“…Mean ( normalx ¯ ) ± 1 standard deviation (SD) was used as the reference interval (RI), as described previously. 4,10,14,15 Gross examination was analyzed qualitatively and reported as a percentage. The results of the chemical examination included SG and pH and are reported as average ranges including SD.…”

“…8,11,16,24,27 However, it is an underused, useful tool in marine mammal veterinary medicine that would allow assessment of early signs of renal and metabolic diseases that could occur without clinical signs. 10,23 We report herein baseline urine values for normal chemical and microscopic variables for common bottlenose dolphins living under human care.…”

Urinalysis Reference Intervals between Rough-Toothed Dolphins (Steno bredanensis) and Common Bottlenose Dolphins (Tursiops truncatus) Kept Under Human Care

“…The study was conducted at the Gulf World Marine Park in Panama City Beach, Florida, in November 2019, where both spe-cies are kept alongside each other. The facility had six Steno bredanensis (three females, three males) and 16 Tursiops truncatus (five females, 11 males). The rough-toothed dolphins were wild-born and rescued from a mass stranding in Florida's Gulf of Mexico.…”

“…A sterile 3-ml transfer pipette was used to collect the sediment, transfer it to a microscope slide, and cover it with a coverslip. as none (0), rare (1-5), few (6)(7)(8)(9)(10), some (11)(12)(13)(14)(15)(16)(17)(18)(19), or many (>20). If casts, bacteria, or crystals were present, each type was also noted on the datasheet.…”