Avian Nutrition (JTA 3)

Question 1

What are the most common nutritional issues in psittacines?

Answer 1

Too much fat in diet (seeds)

Low Ca:P ratio

Low sodium, zinc, iron, lysine, & vitamin A

Fowler 8 Ch 21

Question 2

What are the classic lesions of hypovitaminosis A in birds?

What type of diets are risk factors (psittacines)?

Answer 2

Epithelial squamous metaplasia - hyperkeratosis

All seed diets

ZPP ch 32

Question 3

What are the three mechanisms of goiter development in birds?

Answer 3

Iodine +/- selenium deficiency

Ingestion of goiterogens - brassica & crucuferae plants

Hereditary biosynthetic defects

All three lead to hypothyroidism

ZPP Ch 32

Question 4

A recent retrospective evaluated hepatic hemosiderosis in several avian species.

What is the difference between hemosiderosis and hemochromatosis?

What lesions are associated with hemochromatosis?

What dietary components are associated with hemosiderosis?

What species of birds are particularly susceptible?

Two cases in this study had signs consistent with hemochromatosis - what were they?

Is there any difference in the prevalence of hemosiderosis in managed versus free-ranging birds?

Is there any correlation between iron accumulation and the development of disease?

Answer 4

A RETROSPECTIVE STUDY OF HEPATIC HEMOSIDEROSIS AND IRON STORAGE DISEASE IN SEVERAL CAPTIVE AND FREERANGING AVIAN SPECIES
Ayisa Rodrigues de Oliveira, DVM, MS, Daniel Oliveira dos Santos, DVM, MS, Marianna de Paula Martins Pereira, DVM, Tatiane Furtado de Carvalho, DVM, PhD, Herlandes Penha Tinoco, DVM, Angela Tinoco Pessanha, DVM, Maria Elvira Loyola Teixeira da Costa, DVM, Carlyle Mendes Coelho, DVM, Tatiane Alves da Paixao, DVM, PhD, Marcelo Pires Nogueira de Carvalho, DVM, PhD, and Renato Lima Santos, DVM, PhD
Journal of Zoo and Wildlife Medicine 53(2): 455–460, 2022

Key Points:
- Hemosiderosis – intraceullular accumulation in hepatocytes/Kupffer cells of iron without lesions
- Iron storage disease/hemochromatosis – organ damage, impaired function and clinical signs of iron overload
– Clinical signs/lesions: ascites, hepatomegaly, cardiomegaly, coelomic distention, dyspnea, depression, sudden death
- Diet implicated in etiology of iron overload in birds
– Excessive iron ingestion or due to high ascorbic acid in diet which enhances absorption of iron and/or low levels of dietary tannin (iron chelator)
– Especially susceptible species (frugivorous and insectivorous birds 🡪 Paradisaeidae (birds of paradise), Ramphastidae (toucans), Sturnidae (mynahs), Thraupidae (tanagers), Bucerotidae (hornbills), Pipridae (manakins), Trogonidae (trogons) and Psittacidae (red speckled amazon) and Otididae (kori bustard).
– Among Columbidae only frugivorous species seem susceptible while granivorosus species (collared dove) are resistant
- Aim: Retrospectively evaluate the occurrence of hemosiderosis and ISD across a variety of avian taxa
- ~2/3 of birds had some degree of iron accumulation in the liver
- No statistical difference observed in hemosiderin accumulation between families, orders, or origin (whether free-ranging or managed care)
– Similar prevalence of hemosiderosis between free-ranging and managed care
– Has been reported in free-ranging birds with infectious hemolytic diseases
- Positive correlation between iron accumulation and histologic score
- Two birds had signs compatible with ISD
– Bare faced curassow 🡪 apathy, neurologic signs, dsypnea, jaundice, ascites. Histo showed marked cytoplasmic hemosiderin and hepatocellular cord disruption
– First case of ISD in a galliform
– ISD may not always be associated with additional hepatic lesions (fibrosis, biliary hyperplasia, megalocytosis, necrosis, hemorrhage)
- Channel billed toucan 🡪 progressive hyporexia and weight loss. Confirmed with Prussian blue stain with hepatocyte necrosis and megalocytosis
- The intensity of iron accumulation by itself is not predicative of development of clinical disease

Take-Home Message:
- Iron accumulation may occur in a wide range of avian species and in this study there was no difference in prevalence between free-ranging and managed care.
- Positive correlation between iron accumulation and histologic score, but the intensity of iron accumulation itself is not predictive of developing clinical disease