Author: Neil A Forbes BVetMed Dip ECAMS FRCVS; Great Western Exotic Vets; Swindon, United Kingdom
Date: January 13, 2013
Key words: Raptor, bird of prey, falcon, critical, hypermetabolism, malnutrition, Emeraid, ingluviotomy
All clinicians are aware of the great importance of post-operative fluid, nutrition, and medical administration (including analgesia) for thin, sick or recovering raptors, however doing the calculations, and actually administering all products in a welfare friendly and effective manner can be challenging and extremely time consuming.
The aim is to maximize the prognostic opportunity, to optimize the ingestion and absorption of fluid, nutrition and medication, whilst minimizing any negative effects of administration.
Metabolism during critical illness
When injury or disease initially occurs, the body enters an ‘ebb phase,’ where all but core body systems close down to conserve energy, this is associated with clinical shock. The body defense and repair mechanisms then kick in, suddenly requiring increased metabolic energy, this phase is referred to as hypermetabolism. Hypermetabolism most commonly occurs at a time when the patient has a reduced or non-existent appetite, typically not wishing or being able to feed. Where hypermetabolism is concurrent with reduced food intake, protein-energy malnutrition occurs, resulting in an accelerated form of starvation. In the body’s attempt to meet the metabolic requirements, there is a massive depletion in the body’s protein and fat stores — any falconer can associate with this. The failure to fuel the hypermetabolic state results in reduced immune response, delayed healing, weakness of skeletal, cardiac and gastrointestinal muscle, anemia, cachexia, and potentially death.
Nutrition during critical illness
The challenges faced are two-fold:
- Firstly ensuring sufficient food intake (voluntary or forced) without causing undue concurrent stress.
- A diet which the patient can tolerate, process through the gastrointestinal tract, digest, absorb and metabolize, which will in turn meet the nutrient demands of hypermetabolism.
In an ideal case, the patient will voluntarily ingest sufficient appropriate food to meet these nutritional needs, however all too often with sick or injured patients nutritional supplementation will be required. Some patients will respond favorably to oral force-feeding, but in many debilitated patients, this is slow, stressful, and runs the risk of causing significant deleterious effects. In particular when feeding ‘imprint or just well trained falcons,’ repeated casting is extremely stressful and can lead to a range of negative outcomes, such as stress-induced immunosuppression, as well as physical and feather damage. This all sounds very grim, but appreciating the issues enables us to best assess how these needs can be met.
In essence, what is needed is a critical care diet (Box 1). Nutrients are required in formats such that they can be instantly used to make a positive contribution to negate hypermetabolism.
|Box 1. Components of a critical care diet|
Old-fashioned critical-care nutrition was a conventional diet liquidized so it could be tube-fed, however this requires digestion prior to the potential use of the building blocks. Digestion is itself an energy-demanding function. A modern critical-care diet must also be easily absorbed and readily digestible. Such diets must also be easy to mix, such that they can be easily passed down fine (5-6 Fr) catheters, and energy dense, so that the demands of hypermetabolism can be met by reasonable frequency and volumes of feedings.
All falcon veterinarians and keepers appreciate the dilemma of rapid weight loss, with injury or disease. It is an old cliché, but simply making a diagnosis and providing the correct medication or surgical treatment is not enough; we must also support the bird well enough and for long enough to enable it to make a recovery.
Administration of food — three options:
At Great Western Exotic Vets we have provided critical-care support, using a variety of diets and systems for falcons over many years.
Voluntary ingestion is the preferred and optimal solution, so long as the bird will take sufficient volumes of appropriate food to meet its needs. No doubt all readers will be familiar with the principles. A dehydrated bird should not be fed until rehydration has been effected.
Rehydration is achieved with electrolyte administration, intravenously, subcutaneously (although slower uptake), or orally. In the absence of any other evidence a sick or injured raptor should be assumed to be 10% dehydrated, i.e., a 1-kg bird is 100 ml short of fluid. Fluid deficit is replaced 50% in day one (plus maintenance of an additional 100 ml/kg/day), 25% day two (plus maintenance) and 25% day three (plus maintenance).
A large crop of food should never be provided to a sick or weak bird, for risk of inducing crop stasis and sour crop, which rapidly leads to toxemia and death. Instead, small (maximum one-third to one-half full) crops, of readily digested cast-free food (e.g., free of fur, feathers, bones) is provided. By giving cast-free food, instead of waiting for the bird to cast before re-feeding, as soon as the crop is empty, the bird may be re-fed. In this way a small crop may be fed four to five times a day, resulting in successful ingestion and absorption of perhaps twice as much food as would have been normally taken.
Tube feeding is a long-standing and well-recognized technique that has saved many thousands of sick raptors. The technique is employed when a bird is not willing to eat, eat enough, or take its medication. So long as the bird is strong enough to maintain its head above the level of the crop and can pass a liquid form of diet through the intestinal tract without vomiting, then this form of forced nutrition works very well.
Feeding may be repeated four to five times during the day, and will require one or two person physical patient restraint to administer the food (Fig 1). When first feeding sick falcons, initial volumes administered should be small (1% of body weight), but once this is successfully tolerated volumes can typically be increased to 2.5% or even 3%. Any medication required, may be simply added to the gavaged food. This technique is ideal where supplementary feeding is only likely to be required for 2 to 3 days. The value of this technique is maximized where a high-energy-density diet is utilized (see Choice of diet below).
During ingluviotomy tube placement, a 5-6 Fr feeding tube is surgically advanced from a surgical opening in the crop wall, via the distal esophagus to the mid-proventricular region. Where the tube exits the crop it is sewn in place and the syringe attachment end is then sewn to the bird’s back (Huynh 2012). The technique is invaluable with head, neck or crop trauma, such that normal feeding is impaired, or where supplementary feeding or liquid medication is anticipated to be required for a protracted period, especially in well trained or imprint falcons. In such cases, the bird will typically remain standing unrestrained on block or glove, whilst food is administered via the tube (Fig 2).
After each use, the feeding tube is flushed through with clean water and the end of the tube is closed. In rare occasions, the bird may attempt to chew or remove the end of the tube, in which case a jacket is applied around the hawk, with ties running diagonally across the bird’s chest, from left shoulder to right hip and right shoulder to left hip (Fig 3).
Choice of critical-care diet
So with administration covered, the only matter remaining is the choice of critical-care diet. Various commercial diets, typically pet animal recovery diets, have been available and used for many years. Whilst these diets have been useful, they were never designed with birds in mind, and some birds will vomit these diets. Maintaining or gaining patient weight can also be challenging, as the diets are not optimally energy dense. This facility has used a number of different preparations over the previous 30 years. To date all options, whilst sequentially acceptable, (being the best option at the time), were each surpassed by alternatives. To an extent, the choice will be driven by availability, storage facilities, and other factors.
The product currently considered to be ideal and preferable is Lafeber’s EmerAid Carnivore Critical-Care Diet (Box 2), the first semi-elemental diet designed for use in carnivores. As a semi-elemental diet, EmerAid is comprised of essential building blocks, which can be immediately assimilated and used in a positive manner as soon as they are fed.
|Box 2. Features of EmerAid Carnviore|
EmerAid is provided as a dry powder in sealed sachets or tubs. The shelf-life of EmerAid Carnivore is approximately 18 months from the date of manufacturing, stored in a cool dry place. Storage may be extended by freezing unopened packets. Once EmerAid is opened, it should be kept refrigerated and should be used within 6 months of opening. When using the product, care must be taken not to contaminate the open container with utensils, as bacterial proliferation may subsequently occur.
In the past 18 months, Great Western Exotic Vets has been very fortunate to work on a science-led project, developing and testing improved systems for raptor critical fluid and nutritional support. The results of the ingluviotomy tube placement as a feeding tool are discussed fully in Huynh et al (JAMS In Press) and will not be discussed here, save to say with appropriate care, it is a vitally useful and successful technique.
In respect of case results and outcome using EmerAid Carnivore, this is slightly challenging as cases vary in status at presentation, pathology, and etiology, and as such they are not a controlled group. Furthermore patient could not be ascribed critical-care diet on a randomized basis, as all patients presented to this clinical facility had to be provided with the optimal diet based on clinical evidence. With all commercial convalescent diets previously used, difficulties were encountered with some birds vomiting food or failing to maintain or gain weight. Whilst using EmerAid, the groups’ findings have been that no raptors vomited the diet after feeding. The weights of all birds were maintained or increased. In cases where a body weight increase was required, this was achieved, if necessary by increasing volume or frequency of feeding.
The use of ingluviostomy tube feeding, together with EmerAid Carnivore has proven invaluable in highly debilitated birds, those on long-term feeding or medication and for highly trained and imprint birds where repeated casting is contraindicated.
Forbes NA. Optimising post-surgical outcome with appropriate nutritional and fluid support. Proc Brit Vet Zool Society Edinburgh Conference. 2012.
Huynh M, Brandao J, Sabater M, LVM, Forbes NA. Pharyngostomy tubes as a method of nutritional management in raptors: Case series. Proc Assoc Avian Vet Lake Worth. Florida, 2012. P. 33.
Huynh M, Brandao J, Sabater M, LVM, Forbes NA. Esophagostomy tube as a method of nutritional management in raptors: Case series. J Avian Med Surg: In Press.