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Abstract

Objective—To determine the effects of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs.

Animals—10 healthy neutered dogs.

Procedures—Each dog received dexamethasone (0.01 mg/kg), synthetic ACTH (5 μg/kg), or saline (0.9% NaCl) solution (0.5 mL) IV at intervals of ≥ 30 days. Plasma endogenous ACTH concentrations were measured before (baseline; time 0) and 1, 8, 12, and 24 hours after drug administration; serum cortisol concentrations were measured before and 1 hour after synthetic ACTH and saline solution administration and 8 hours after dexamethasone administration.

Results—Analysis of serum cortisol concentrations confirmed effects of drug administration. Dexamethasone significantly decreased the endogenous ACTH concentration from the baseline value at both 8 and 12 hours. Synthetic ACTH administration significantly decreased the endogenous ACTH concentration from the baseline value at 8 hours. Saline solution administration had no significant effect on endogenous ACTH concentration.

Conclusions and Clinical Relevance—Dexamethasone and synthetic ACTH administered IV at doses used routinely during testing for hyperadrenocorticism caused significant but transient reductions of endogenous ACTH concentrations in healthy dogs. Thus, a 2-hour washout period following ACTH stimulation testing before collection of samples for measurement of the endogenous ACTH concentration may be insufficient. Although this effect has not been verified in dogs with hyperadrenocorticism, these data suggested that samples for measurement of endogenous ACTH concentrations should be obtained before or > 8 hours after initiation of an ACTH stimulation test or before or > 12 hours after the start of a low-dose dexamethasone suppression test.

Full access
in American Journal of Veterinary Research

Summary

Eighteen 9- to 10-week old Beagles were fed casein-based diets (4,710 kcal of metabolizable energy /kg of body weight) containing either 12, 80, or 160 mg of iron/kg of diet. Growth and feed consumption were monitored throughout the 47-day study. Hematocrit (Hct), hemoglobin (Hb) concentration, mean corpuscular volume (mcv), mean corpuscular hemoglobin (mch), mean corpuscular hemoglobin concentration (mchc), rbc numbers, erythrocyte protoporphyrin (ep) concentration, serum iron concentration, serum total iron-binding capacity (tibc), and serum ferritin concentration were determined weekly. Growth rate and feed efficiency were not significantly influenced by dietary iron content. At 14 days, Hb concentration, Hct, mcv, mch, rbc numbers, and serum iron concentration were significantly (P < 0.05) lower in dogs fed the 12 mg/kg diet, and remained significantly low for the remainder of the study. Erythrocyte protoporphyrin concentration increased significantly (P < 0.05) by 14 days in dogs fed the basal diet, and remained significantly high relative to that in dogs of the other dietary groups for the remainder of the study. Serum ferritin concentration decreased in dogs of the group fed the basal diet, with a significant (P < 0.05) difference beyond day 42. Differences in Hct, mch, mcv, or hemoglobin, serum iron, serum ferritin, or ep concentration were not found between groups fed 80 and 160 mg of iron/kg of diet. Liver nonheme iron content was significantly (P < 0.05) affected by dietary iron content.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Case Description—3 adult (24- to 43-year-old) Atlantic bottlenose dolphins (Tursiops truncatus) with chronic episodic malaise and inappetence associated with high serum aminotransferase (alanine aminotransferase and aspartate aminotransferase) activities, high serum iron concentration, and serum transferrin saturation > 80% were evaluated.

Clinical Findings—Results of histologic examination of liver biopsy specimens revealed hemosiderosis in all 3 dolphins. Except for chronic lymphocytosis in 1 dolphin, results of extensive diagnostic testing revealed no other abnormalities. For each dolphin, a diagnosis of iron overload of unknown origin was made.

Treatment and Outcome—Phlebotomy treatment was implemented to reduce body stores of iron. Each phlebotomy procedure removed 7% to 17% (1 to 3 L) of estimated blood volume. Treatment consisted of an induction phase of weekly phlebotomy procedures for 22 to 30 weeks, which was complete when serum iron concentration and aminotransferase activities were within reference ranges and serum transferrin saturation was ≤ 20% or Hct was ≤ 30%. Total amount of iron removed from each dolphin was 53 to 111 mg/kg (24.1 to 50.5 mg/lb) of body weight. One dolphin required maintenance procedures at 8- to 12-week intervals when high serum iron concentration was detected.

Clinical Relevance—Although the cause of the iron overload and high serum aminotransferase activities remained unknown, phlebotomy treatment successfully resolved the clinicopathologic abnormalities, supporting a role of iron overload in the hepatopathy of the 3 dolphins.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate annual survival and mortality rates and the longevity of a managed population of bottlenose dolphins (Tursiops truncatus).

Design—Retrospective cohort study.

Animals—103 bottlenose dolphins at the US Navy Marine Mammal Program (MMP).

Procedures—Population age structures, annual survival and crude mortality rates, and median age at death for dolphins > 30 days old were determined from 2004 through 2013.

Results—During 2004 through 2013, the annual survival rates for MMP dolphins ranged from 0.98 to 1.0, and the annual crude mortality rates ranged from 0% to 5%, with a mean of 2.7%. The median age at death was 30.1 years from 2004 through 2008 and increased to 32 years from 2009 through 2013. The maximum age for a dolphin in the study was 52 years.

Conclusions and Clinical Relevance—Results indicated that the annual mortality rates were low and survival rates were high for dolphins in the MMP from 2004 through 2013 and that the median age at death for MMP dolphins during that time was over 10 years greater than that reported in free-ranging dolphins. These findings were likely attributable to the continually improving care and husbandry of managed dolphin populations.

Full access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To evaluate the impact of oral megestrol acetate (MA) administration on adrenal function in male bottlenose dolphins (Tursiops truncatus).

DESIGN Serial cross-sectional study.

ANIMALS 8 adult male dolphins, all of which were receiving MA at various daily doses (range, 0 to 60 mg, PO) for the control of reproductive behavior.

PROCEDURES Blood samples were collected every 2 weeks for 1 year from dolphins trained to voluntarily provide them. Cortisol, ACTH, and other hormone concentrations were measured in serum or plasma via radioimmunoassay or ELISA. Fecal samples, also provided by dolphins voluntarily, were assayed for glucocorticoid metabolite concentrations. Effects of daily MA dose on hormone concentrations were evaluated.

RESULTS Daily MA doses as low as 10 mg strongly suppressed cortisol secretion in nearly all dolphins, and except for a single measurement, no dolphin had measurable serum concentrations at doses ≥ 20 mg. Variations in serum cortisol concentration were unrelated to season but were directly related to ACTH concentrations, suggesting primary effects upstream of the adrenal gland. Cessation of MA administration resulted in almost immediate restoration of measurable serum cortisol concentrations, although concentrations continued to rise in a few dolphins over the following weeks to months.

CONCLUSIONS AND CLINICAL RELEVANCE Caution should be exercised when administering MA to control reproductive behavior in male dolphins. Because the hypothalamic-pituitary-adrenal axis appeared to be sensitive to even small doses of MA in dolphins, duration of treatment may be the most critical consideration.

Full access
in Journal of the American Veterinary Medical Association