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Nutrient Requirements

Adult Cockatiels (Nymphicus hollandicus) at Maintenance Are More Sensitive to Diets Containing Excess Vitamin A Than to Vitamin A–Deficient Diets

Elizabeth A. Koutsos^*, Lisa A. Tell, Leslie W. Woods and Kirk C. Klasing^*,4

^* Department of Animal Science; Department of Medicine and Epidemiology, School of Veterinary Medicine; and California Animal Health and Food Safety Lab, University of California–Davis, Davis, CA 95616

⁴To whom correspondence should be addressed. E-mail: kcklasing{at}ucdavis.edu.

The purpose of this experiment was to examine the physiological responses of adult cockatiels at maintenance to dietary vitamin A (VA) concentrations, and to identify concentrations associated with deficiency and toxicity. Adult cockatiels at maintenance (n = 22, 2–3 y of age) were fed a diet of 0, 600, 3000 or 30,000 µg VA/kg (0, 2000, 10,000 or 100,000 IU), and monitored for signs of VA deficiency or toxicity for up to 706 d. The analyzed diet concentrations were 0, 835, 2815 and 24,549 µg/kg, respectively. After 269 d, birds fed the 30,000 µg/kg VA diet had greater plasma retinal concentrations, markedly intensified vocalization patterns, pancreatitis and multifocal accumulation of lymphocytes in the lamina propria of the duodenum compared to birds fed the 600 µg/kg diet (P < 0.05). The 3000 µg/kg VA diet induced increased plasma retinol, splenic hemosiderosis and altered vocalization patterns (P < 0.05), although not as striking as those induced by the 30,000 µg/kg VA diet. The secondary antibody response was reduced after 225 d and vocalization patterns were altered in birds fed 0 µg/kg VA (P < 0.05), but after almost 2 y there were no changes in body condition, plasma retinol, organ pathology or classical signs of deficiency such as squamous metaplasia of nasal epithelia. Thus, adult cockatiels at maintenance were more susceptible to VA toxicity than to VA deficiency and concentrations 3000 µg VA/kg diet can cause toxicity. It is possible that disturbances in VA nutrition contribute to the widespread incidence of behavioral problems reported in companion birds.

KEY WORDS: • cockatiel • deficiency • requirement • toxicity • vitamin A