Blood analytes in California sea lion Zalophus californianus pups: reference intervals and malnutrition effects, from admission to rehabilitation.

Blood analyte data are limited for California sea lion Zalophus californianus pups despite frequent admission to rehabilitation facilities. The objectives of this study were to establish blood analyte reference intervals for rehabilitated California sea lion pups (n = 58) deemed clinically normal for release and for free-ranging California sea lion pups (n = 37) during routine health assessment on San Miguel Island, California, USA; to compare manual white blood cell (WBC) differentials to an in-house hematology analyzer (ProCyte Dx); and to evaluate paired blood analyte data of pups affected by malnutrition at time of intake compared to release and in comparison to free-ranging conspecifics. From 2020 to 2022, all stranded pups were thin or emaciated with various additional health concerns at admission (e.g. pneumonia, abscesses, ocular injuries). Average time in rehabilitation was 101 ± 27 d. Reference intervals were established for successfully rehabilitated and free-ranging pups. WBC differential counts evaluated by the analyzer compared to manual blood film review were inconsistent. Blood analytes of pups differed between intake and release, and with free-ranging conspecifics. These findings provide evidence for systemic inflammation, nutritional imbalances, and metabolic derangements in stranded malnourished pups and elucidate physiological changes undergone by growing pups during rehabilitation, particularly as they differ from free-ranging conspecifics. Moreover, the results herein underscore the importance of blood film review for obtaining accurate data for the establishment of reference intervals. These data aim to support clinical assessments of sea lion pups at intake and at release in context of other clinically relevant release criteria.