Birch Heath Veterinary Clinic

Hypocalcaemia is a recognised syndrome in Grey parrots in captivity although the

aetiology is still unconfirmed. It is proposed that seed based diets containing low

calcium and vitamin D

The group consists of 100 grey parrots kept in separate adult pairs on a commercial

parrot farm in the UK. The birds are housed in the same building in separate cages 2m

by 1.5m. The birds were examined by endoscopy, routine blood analysis (including

PCR tests for circo virus, polyoma virus and chlamydia) and faecal analysis to ensure

they were healthy prior to use in the group. The birds were initially kept on a

traditional seed mix diet with fruit supplementation for one year. The ultraviolet light

levels were constantly monitored during the study. Blood samples were taken from 40

birds (20 birds of each sex) chosen randomly from the building under sevoflurane

anaesthesia. Half of this group were then placed on Harrison’s High Potency Course

Pellets and the other 20 birds remained on the seed mix as a control group. After

another 12 months further blood tests were taken from the 40 birds.

The building is now being lit artificially with ultraviolet tubes for a further year whilst

keeping the diets the same. A third and final sample will then be taken in September

2003. All the blood samples were analysed using a standardised biochemical and

haemological profile. In addition the samples were analysed for 25(OH) vitamin D

Calcium is distributed in the plasma as free calcium ions, bound calcium (mainly to

albumin and complexed calcium (bound to anions). The traditional measurement of

total calcium does not give the clinician an accurate picture of the bio-available

calcium in exotic species. Ionised calcium will be kept within a tight range compared

with total calcium values that will vary widely depending on protein levels in the bird.

The measurement of ionised calcium is considered to be a more accurate reflection of

the calcium status of a patient. Ionised calcium is kept within a tight range in all

species.

Hypocalcaemia is common in grey parrots. The aetiology of the disease is still

uncertain. Ionised calcium levels were measured using an ion-selective electrode in

100 grey parrots to produce a normal range for the breed. The birds were considered

healthy on the basis of a standardised clinical examination and routine health profiles.

Samples from the 40 grey parrots received into the laboratory were measured for total

and ionised calcium. All samples received were initially screened both for biochemical

and haematological parameters prior to being assayed for ionised calcium, where

possible, clearly abnormal results were taken away from the core values used for the

final guide range production. All birds assayed had undergone veterinary inspection as

part of their annual veterinary health check prior to being sampled. Any bird, which

was obviously not healthy so far as the inspecting veterinary surgeon was concerned,

were not sampled. For the purpose of the production of guide ranges, only, as far as

clinical and laboratory examination could state, were healthy birds tested as part of a

routine health screen.

40 Grey Parrots as described were analysed for ionised and total calcium as detailed,

their results are listed below:

The results were subjected to statistical analysis using a modified t test to produce a

normal range for ionised calcium of

Vitamin D deficiencies are common in captive birds kept indoors in a UV deficient

environment with insufficient dietary vitamin D. The domestic fowl does not have a

dietary requirement for vitamin D if it receives adequate UV light in the 285-315nm

spectrum. Psittacines are commonly fed a seed based diet deficient in vitamin D. In

addition psittacines kept indoors receive inadequate UV for cutaneous synthesis. It is

well established that grey parrots are particularly susceptible to hypocalcaemia. It is

40

Ionised Calcium mmol/l Total Calcium mmol/l

postulated that seed based diets deficient in vitamin D are a possible contributory

factor to this condition leading to nutritional secondary hyperparathyroidism but no

study has measured vitamin D in psittacines. The aim of this study was to assess the

vitamin D status of a colony of grey parrots fed an unsupplemented seed diet.

Vitamin D status is best assessed by assay of 25-Hydroxy Vitamin D due to its long

half-life compared with other vitamin D metabolites. Traditionally radio

immunoassays (RIA) have been used to assay 25-Hydroxy Vitamin D but more

recently enzyme immunoassays (EIA) have become available with the advantages of

both simplicity and economy.

100 grey parrots were fed on a mixed seed diet with no additional supplementation.

The group were kept indoors under artificial lighting. 40 birds were selected at random

and blood samples taken from the brachial vein under sevoflurane anaesthesia. The

blood samples were subjected to a standard haematological and biochemical profiles

and the birds had a standardised clinical examination: any birds considered unhealthy

were withdrawn from the study. This left a sample size of 34 healthy grey parrots.

The IDS OCTEIA 25-Hydroxy Vitamin D kit was used on the samples for the

quantitation of 25-Hydroxy vitamin D. Each sample was assayed in duplicate. The

results indicated a range of 25-Hydroxy Vitamin D between 5.1-380nmol/l with a

mean of 119nmol/l.

The results show a wide variation in the level of 25-Hydroxy Vitamin D in seed fed

grey parrots. In mammals vitamin D levels below 50nmol/l are considered a vitamin D

deficiency. Chronic vitamin D deficiency would lead to hypocalcaemia due to

nutritional secondary hyperparathyroidism.

Analysis of the diet using the Zootrition program indicated a vitamin D level of 0.1%.

It is suggested that minimal levels for vitamin D in the domestic fowl is 0.4%.

This study suggests that the vitamin D levels were low in 18 of the 34 birds sampled.

All the birds had normal ionised calcium levels at the time of the study. Further

studies on the same group are being carried out to analyse the effect of increasing

levels of UV light in the 285-315nm spectrum and dietary changes to pelleted diets on

the vitamin D levels. Initial observations on 5 grey parrots kept on pelleted food

(Harrison’s High Potency Course) under the same husbandry conditions indicate

higher levels of 25-hydroxy vitamin D compared with the seed fed birds. Further tests

on the study birds will see if there is a statistically significant difference between the

vitamin D3 levels in seed fed greys and pellet fed greys in September 2002.

The author is very grateful for financial assistance from the RCVS Trust and

Harrison’s International Bird Foods. Thanks must also go to Nigel Harcourt-Brown

for his enthusiasm and support for this project

Michael Stanford BVSc MRCVS August 2002-08-26

Barber PJ, Elliott J, Torrance AG (1993): Measurement of feline intact parathyroid hormone:

Assay validation and sample handling studies.