Effect of age, sex, and season on the variation in blood analytes of a clinically normal ex situ population of killer whales (Orcinus orca)

Abstract

BackgroundThe effects of sex, age, and season on blood analyte concentrations have not been investigated for the killer whale (Orcinus orca). Defining these changes provides background data for improving the care of managed populations and defines normal changes that could occur in wild counterparts.ObjectivesWe aimed to define hematologic and serum biochemical variation by age, sex, and season for an ex situ killer whale population.MethodsBlood samples collected from killer whales during normal wellness exams were retrospectively identified. Killer whales were categorized by age; calf (0‐2.9 years), juvenile (3‐10.9 years), early adult (11‐20.9 years), adult (21‐30.9 years), and aged (>30.9 years); sex; and season. Standard CBC and biochemistry were collated, and only samples without evidence of disease were used. A mixed effects maximum likelihood regression with animal identification (ID) as the random effects variable was used to compare groups with a significance set at P ≤ 0.01.ResultsAll analytes differed by age, while only four differed by sex. Red blood cell parameters and associated renal analytes increased with age, while liver‐associated analytes and glucose decreased. Season affected 59% of the blood analytes.ConclusionsAged killer whales showed strong evidence of altered physiology as compared with younger animals. Anemia did not develop with age as was observed in one bottlenose dolphin population. Observed decreases in renal function could be caused by chronic disease or dehydration. Decreases in immune function parameters suggest immune senescence. These results provide background data for evaluating the health of managed and free‐ranging killer whales.

Circulating and Excreted Corticosteroids and Metabolites, Hematological, and Serum Chemistry Parameters in the Killer Whale (Orcinus orca) Before and After a Stress Response

“…variation in serum glucose in clinically healthy killer whales under routine, non-stressed conditions (Nollens et al, 2019). In addition to the acute hyperglycemia, glucose concentrations significantly correlated with serum cortisol and corticosterone throughout the study period.…”

“…To look for effects of an acute stress response on killer whale hematology and serum chemistry profiles, the following analytes were measured at each stage as previously described (Robeck and Nollens, 2013;Nollens et al, 2019): red blood cells (RBC); hemoglobin (Hb); hematocrit (Hct); mean corpuscular volume (MCV); mean corpuscular hemoglobin (MCH); mean corpuscular hemoglobin concentration (MCHC); platelet count; mean platelet volume (MPV); total white blood cells (WBC); absolute segmented neutrophil count (Abs seg); absolute monocyte count (Abs mono); absolute lymphocyte count (Abs lymph); and absolute eosinophil count (Abs eos). For serum chemistry analysis, the following analytes were measured: glucose; blood urea nitrogen (BUN); creatinine (Creat); total bilirubin (TBili); cholesterol; triglyceride; total protein (Tprotein); albumin; globulin; alkaline phosphatase (ALP); alanine aminotransferase (ALT); aspartate aminotransferase (AST); gamma glutamyl transpeptidase (GGT); creatine kinase (CK); lactate dehydrogenase (LDH); calcium; phosphorus; sodium; potassium; chloride; CO 2 ; and iron.…”

“…The fixed effect variables (step 1 of the LMM), in addition to the factorial variable time-stage, included the dependent variable (steroid or serum chemistry/hematology parameter) and independent fixed effect variables (animal age [continuous variable] and sex [coded 0,1]) and their interaction. Animal age and sex and their interaction were included as fixed effects variables to control for potential effect that these variables may have on the dependent variables being evaluated (West et al, 2014;O'Brien et al, 2017;Robeck et al, 2017;Nollens et al, 2019). The random effect, or intercept (reduced model), variable, animal ID (stage 2, n = 13, coded 1-13), was used to control for the variance associated with an unequal number of repeated measures per animal.…”

“…A comprehensive evaluation of serum chemistry and hematology parameters in killer whales spanning multiple years and evaluating age, sex, and season in a clinically healthy, managed killer whale population has recently been published (Nollens et al, 2019). However, to our knowledge, a study of hematology and serum chemistries in killer whales during an acute stress event has not been performed.…”

“…In zoo-based killer whales, blood samples for hematology and serum chemistry are routinely tested as part of preventative animal health assessment programs, and monitoring occurs throughout all phases of growth, development, reproduction, and senescence (Nollens et al, 2019). Although normal reference ranges during these varied biological phases of life were established, almost no information exists on the relationship of hematological and serum chemistry parameters to GCs and/or MCs in the killer whale.…”