Proceeding of the SEVC Southern European Veterinary Conference

Transcription

1 Proceeding of the SEVC Southern European Veterinary Conference Oct , 2008 Barcelona, Spain Reprinted in the IVIS website with the permission of the SEVC

2 Other Companion Animals Avian Clinical Nutrition Dr.J.Jiménez Of all the detrimental factors affecting the health of pet birds, inadequate diet is certainly the most important. Most of the bird pathologies seen in the consulting room will be directly or indirectly related to nutritional imbalances.the aim of this presentation is to aid the veterinarian in assessing objectively the diet of his/her patients, detect nutritional imbalances during physical examination, correct these imbalances and help the owner improve the diet. Most of these observations refer mainly to psittacines. How do psittacines feed in the wild? Amongst the dozens of most frequent species seen in the consulting room, the variety between them is remarkable. Some, like Ara chloroptera are frugivorous, others, like budgerigars (Melopsittacus undulatus) and cockatiels (Nymphicus hollandicus) are granivorous, whereas other are omnivorous. Some have very specialised diets, such as lories eating nectar, or african grey parrots (Psittacus erithacus). African greys are a paradigmatic example of specialisation. Its diet is based on the fruit of palm oil (Elaeis guineensis), which contains high levels of saturated and mono-unsaturated fat, in contrast to the oil seeds available in commercial foods, and with the sources of fat in many commercial pellets, which contain mostly poli-insaturated fat. In general african greys and macaws need diets with higher fat content than amazons, cockatoos and the rest of psittacines. The majority of psittacine birds will spend 50% of their time in the wild foraging for food. The diet offered in captivity does not tend to demand hardly any time investment, which in turn leads to behavioural problems and obesity. How are psittacine birds fed in captivity? Traditionally, psittacine birds have been fed a mixture of seeds supplemented with fresh vegetables. The introduction of commercial pellets has represented a vast qualitative improvement, as this helps the average owner in the task of offering his bird a balanced diet. Although both methods have advantages and disadvantages (Table 1), it is generally recommended to base the diet on good quality pellets.

3 Table 1. Advantages and disadvantages of both types of diet in psittacine birds. How to improve the diet? Conversion to pelleted diets In order to make the transition possible, both the owner and the bird have to be convinced. To make the conversion a success the owner has to be motivated and the veterinarian will have to provide the motivation and all the necessary advice. No method is infallible but there are certain techniques which will facilitate the process¹. The fact of eating is a social activity for psittacines. The owner can nibble the food and then offer it to the bird or other persons while the bird can see it. A very useful resource is to use other birds already used to the new diet as teachers. The new food can be offered in different ways: mixed with their favourite treats (e.g. yoghourt), moistened with juice, or mashed and sprinkled on top of fruits or other foods. It should always be associated to pleasant moments and play time. Some birds such as cockatiels will naturally forage for seeds on the ground. In these cases, we can sprinkle the new food over the ground in order to try to stimulate its consumption. The seeds and the new food can be mixed in the feeding bowl and after 1-2 weeks we can gradually reduce the amount of seeds until it is non existent. Although a gentle gradual introduction is generally desirable, sometimes a more drastic approach can be more effective in some birds, offering pellets as the only food alternative during the day and only allowing the feeding of other types of food during 5-15 minutes twice a day. It could take up to 4-5 days for the transition to take place. During the process we will have to closely monitor the state of the bird, the production of excrements and the possible weight loss (an approximate maximum of 10-15%), since some individuals might reject the new diet to a dangerous extreme. If the transition proves very difficult, it can be attempted on a different brand, perhaps more palatable. If the conversion to pellets is not viable. The mixtures of oil seeds result very palatable and encourage an excessive consumption of fat. Birds will naturally eat until the energy requirements are covered and fat provides plenty of energy. Therefore the excessive consumption of fat will lead to an inferior ingestion of other foods higher in vitamins, amino acids and trace elements, leading to deficiencies. The amount of oil seeds should be rationed in order to stimulate the consumption of other types of foods. This problem is less relevant in smaller sized psittacines such as cockatiels, since they are better adapted to a granivorous diet, and the seeds in their diet (with a high proportion of millet) tend to be less fatty. The percentage of protein in the seeds is usually adequate but tends to lack essential amino acids (lysine and methionine). In order to improve this, we do not necessarily have to increase the amount of protein but supplement instead the diet with foods rich in these amino acids, such as pulses (preferably cooked, alternatively soaked or germinated) or alternatively administer small amounts of animal protein (hard-boiled egg, low fat cheese and small pieces of meat). Seeds have in general a low content of calcium and some liposoluble vitamins (particularly vit.a). For this reason, and to correct this deficiency, it is advisable to supplement the diet with preparations high in calcium and vitamins sprinkled on the fresh foods (not in the water)². The addition of fruit, vegetables and greens will increase marginally the amount of vitamins provided. It is advisable to avoid avocado because some varieties are toxic. Calcium can also be made available as a soluble grit in the form of oyster shells or similar, or powder supplementation. Nutritional diseases We should try to find out about the different types of food offered to the bird and the relative frequency, as well as the amount effectively consumed of each one. This information is difficult to ascertain and interpret and, even so, it might only allow us to have a vague idea of the nutritional quality of the diet. During the clinical examination we should pay special attention to any signs of malnutrition. Obesity is difficult to evaluate unless it is very evident, and might not be noticeable until we have the bird in our

4 hand. Subcutaneous fatty tissue tends to accumulate in chest and abdomen. The monitoring of the body weight will be of help. Hepatic lipidosis is a common complication in obese birds. Obese animals have to be subject to a diet with lower energy content and an increased level of activity. Fruit and vegetables usually have very low energy content; therefore the increase in the proportion of this type of food could be beneficial. Weight loss should be progressive (maximum 1-2% per week). For the well-trained eye, the quality of the feathers can be an excellent indicator of the nutritional status of the bird. Deficiencies of aminoacids tend to cause changes in the coloration of the feathers, such as green feathers turning black or yellow. Hypovitaminosis A is associated with the erosion of the plantar surface and pododermatitis, hyperkeratosis in the legs of canaries, predisposition to oculo-respiratory diseases, wearing of choanal papillae and sublingual abscesses and around the area of the neck. The latter are more predominant in African greys. The safest way to treat vitamin A deficiency is to provide the animal with foods rich in beta-carotenes (carrot, garden produce and vegetables), which are its natural precursors. In severe cases, we can administer IU of vitamin A via intramuscular injection. The indiscriminate use of supplements has led to numerous cases of hypervitaminosis A. The majority of the commercial products also contain various amounts of vitamins D and E, often in excess. Hypovitaminosis D is very unlikely if there is access to solar light or artificial sources of UVB. African grey parrots and macaws seem particularly sensitive to iatrogenic hypervitaminosis D. The deficit of calcium is more likely in situations of high requirements: females laying eggs or growing young birds. It can lead to soft or deformed eggs, dystocia or metabolic bone disease. One particular form of hypocalcaemia, characteristic of African greys, is hypocalcaemic tetany. It is not yet clear whether the cause of this syndrome is only nutritional. African greys seem to have some difficulties to rapidly mobilise bone calcium and to regulate calcaemia³. In cases of tetany, we can administer calcium gluconate (100 mg/kg im, e.g.injectable calcium Braun 1ml/kg). African greys will seldom be affected by this syndrome if fed the right diet and having access to solar light. Thyroid hyperplasia (goitre) due to iodine deficiency in cockatiels has been repeatedly mentioned in the literature as a common problem but, in the author s experience, the incidence in our surroundings is practically zero. Another common problem Ramphastidae (toucans) and Sturnidae (minahs and others) is the disease due to accumulation of iron or also known as haemosiderosis, which affects mainly the liver. The excess of iron in the diet will play a role in the disease, but there possibly are other factors involved regarding the difficulty in this species in regulating the intestinal absorption of iron. Atherosclerosis is defined as the thickening of the arterial wall associated to lipid deposits. African greys and amazons seem to be predisposed and there is growing evidence that there might be many birds affected (2.1 to 4.6% according to different studies) 4 The aetiology in birds is probably multifactorial, including diets with excessive content of lipid and cholesterol, stress and systemic diseases which interfere with the lipid metabolism5 The ante mortem diagnosis is not easy but we might detect hypertension or radiodensities in aortic arteries. Nutritional support in hospitalised patients Sick birds presenting with anorexia will need force-feeding by crop tube. Before we proceed with this

5 technique, we must ensure that the patient is properly hydrated and stable enough to tolerate oral feeding. The metallic round-tip gastric tubes are ideal for this purpose. In large psittacines we can also use flexible gastric tubes and mouth gags. The neck should be fully extended and the correct placement of the tip of the tube should be confirmed by palpation. The volume administered in each feeding depends on the body condition of the patient and the species6 : as a rough approximation, we can administer 1 to 2.5% of the body weight (canaries ml; budgerigars 1-2 ml, cockatiels 2-4 ml, african greys and amazons ml, large macaws ml) 3 to 4 times a day. It is advisable to start with smaller volumes and diluted feeds, in order to achieve gradual increase in further feeds. There are several enteric products available on the market for sick birds (Emeraid Psittacine-, Lafeber Products). Similar products formulated for humans can also be adequate short term: they are highly digestible, fairly balanced liquids. Another option would be high energy foods for hand-rearing. References 1. Donoghue S, Stahl S: Clinical nutrition of companion birds. Jour Av Med Sur 1997; 11(4): Stahl S, Kronfeld D: Veterinary nutrition of large psittacines. Sem Av Exot Pet Med 1998; 7(3): Koutsos E, Matson K, Klasing K: Nutrition of birds in the order psitaciformes: a review. Jour Av Med Sur 2001; 15(4): Garner M, Raymond J: A retrospective study of atherosclerosis in birds. Proc AAV 2003; Lumeij T, Ritchie B: Cardiology. En: Ritchie BW, Harrison GJ, Harrison LR (eds): Avian medicine: Principles and application. Lake Worth, Wingers Publishing, 1994; Quesenberry K: Avian nutritional support. En: Kirk R, Bonagura J (ed): Kirk's Current Veterinary Therapy XI: Small Animal Practice, Harcourt, 1992;