(by neil Forbes FRCVS)
General Aims - To feed a diet as similar to the consumers natural prey species that the bird would enjoy in the wild, whilst at the same time ensuring the correct food quantity, quality, wholesomeness and storage methods.
As most keepers will appreciate, the feeding of neonates, involves a whole set of different problems, so in order to keep things simple, we will consider feeding adult birds only.
PROBLEMS ENCOUNTERED WITH FEEDING ADULT BIRDS
Source of Food - Irrespective of the food type, it is obviously essential that one is as far as possible 100% certain as to the quality, source, method of killing, freezing and storage of the food.
Any ex-wild source of food eg. pigeon, game, etc. must be considered. We always have to ask the question, why did the animal / bird get run over in the first place? Was it simply bad luck, or was it unwell that day? Whatever the reason, it failed the test of life that day and should be considered as being potentially unwholesome. Such birds can carry bacterial infections such as Tuberculosis, Salmonella or virus infections such as Paramyxovirus, Adenovirus or Rotavirus, or be contaminated with a poison e.g. alphachloralose. Any wild sourced food should be in good body condition, have been caught and killed by physical means, and on examination of the carcass should look in all respects to be thoroughly wholesome and free of disease. It is crucial that the abdomen of such birds is always opened and the surface of the liver checked. If any small white spots are present on or in the liver, (often indicative of avian tuberculosis) the whole carcass must be rejected,
Rifle shot, ferreted or trapped rabbit, pigeon or other should not be assumed to be free of pathogens or indeed lead. Recently Richard Jones, my falconer colleague, acquired some rifle 'head shot' rabbits for his Harris hawk. For interest we X-rayed these rabbits, prior to feeding. In each case, as the rifle shot had penetrated the
Text Box: Feeding Raptors by Neil Forbes FRCVS
base of the skull, it had left a myriad of lead fragments, any of which would have been plenty large enough to cause disease and death of the bird. Ferreted or trapped rabbits are the cause of lead poisoning cases every year. Often it is the time that a rabbit has been 'pricked' by some poor shot on a previous occasion, only to carry on running around the countryside, with a few pieces of lead on board. We are not suggesting not to feed such material, but simply to be aware of and quantity the risks. Most importantly to be aware of the signs of lead poisoning, so that if they arise, you get the bird to an experienced avian vet immediately so that the situation can be saved.
SIGNS OF LEAD POISONING - ANY NERVOUS SIGNS WEAKNESS OF LEGS IN PARTICULAR OR WINGS.
Any food such as rats, mice, squirrels or foxes, are less likely to cause any infectious disease to your birds. The reason for this is that most pathogens will only affect one family of animals, i.e. a rodent virus is highly unlikely to affect birds. Conversely feeding any avian derived foodstuff is a potential risk.
In recent years we have encountered several outbreaks, in particular of virus disease, (eg. Adenovirus and Rotavirus), where perfectly healthy commercially sourced quail, day olds, turkey poults etc., have been fed to healthy raptors which have then succumbed to disease and in several cases died. The problem here is that many pathogens including viruses can be harboured by one species (eg. day old chicks), without causing it any harm, i.e. the chick looks and is healthy, but when the chick is eaten, the raptor is infected. Sadly although the virus did not harm the chick it may conversely be deadly
Pigeons form a special risk to raptors on account of their high incidence of Trichomonlasis (frounce). Many falconers believe that if they only feed the breast there is no risk. Sadly this is not true.
Stressed, old, young or ill birds will be most susceptible. Birds in perfect health may avoid the infection, otherwise most wild peregrines would suffer badly. However no risks should be taken, all pigeon which is fed should be frozen completely and thawed before feeding. The duration of freezing is unimportant.
Rabbit - Just occasionally when feeding larger species on rabbit or hare a problem can arise. If the bird is sufficiently greedy it may take the whole thigh (femur) bone of the rabbit. On many occasions the bird will cope with this, however sometimes it will wedge sideways in the crop or proventriculus. This may cause a perforation of the gut lining or an obstruction. The recommendation for such sized birds is to break the femur before feeding the carcass if the bone is taken in two sections no problem will arise
Storage of Food - One has to accept that any food will have a number of bacteria in it, Any delay which occurs between the death of the food, and its freezing (or feeding), will allow that number of bacteria to increase. Any excessive food storage (ie. freezing for more than 3 months), will lead to a deterioration in food quality, in particular the vitamin content. Any delays between thawing the food and its ingestion by the bird, will again allow the numbers of bacteria to increase. Whilst any bird is designed to, and is capable of, safely eating food with a certain bacterial load, if this load is excessive, the bird will not cope, and become ill.
Feeding the Bird which is low in Condition - Many falconers have an obsession about giving casting each and every day. As all keepers should be aware it is important not to feed a bird again until it has brought up the casting from the previous day. If you have a bird, which is low in condition, you do not want to have to wait a full day before you give a further meal. In this situation it is quite permissible, if not essential, that you do not give any casting.
Instead you give a small meal of finely chopped meat, perhaps with a little added saline. As soon as, and not before, the bird has put its crop over it should be given a further small meal.
Sour Crop - 1 would hope that all falconers would be aware of the condition of 'source crop'. If food has passed from the crop into the proventriculus (stomach), stomach acids will act upon it, aiding the digestion as well as preventing any bacterial action on the food. If conversely the food stays in the crop, it is no longer in your fridge being kept nice and cold. Instead it is at body temperature (40-41°C), and yet has no acid acting on it to prevent bactehal decay. In short the food goes off very rapidly, causing the production of toxins (poisons) which very rapidly kill the bird. If your bird is slow to put its crop over, then a small volume (0.5% of the bird's body weight, i.e. 5ml for a 1 Kg bird), of saline should be given by mouth. This will usually quickly result in the crop being put over. If it does not, and the bird does not through the crop back of its own accord, then the food must be removed by milking it back up from the crop. This can be a risky procedure, as any fluid present in the crop will return as the meat is brought back up and the fluid may go down the windpipe causing a fatal pneumonia. Whatever the outcome the bird will need veterinary care and antibiotics.
Sour Crop Prevention - There are certain times when sour crop is particularly common. Any bird which is off colour, stressed, underweight, cold, chilled or which has an over full crop is less likely to put its crop over. In particular this often occurs when a bird is first entered. The keeper has had to drop the weight, perhaps a little too low for comfort, in order to encourage the bird to enter. Having made its first kill, he is so chuffed he rewards her by letting her have a full crop. However the bird being underweight is very hungry, the bird is pleased, so is the falconer, so he lets her have a really good fill. The only trouble is, all too often, too full. The
consequence is 'SOUR CROP'. So never let a bird over fill the crop. It is not healthy.
Feeding the Vomiting Bird - Vomiting may arise in raptors as a consequence of a whole range of different conditions. The whole situation will almost inevitably require veterinary care, although a few general points are mentioned here. A bird which is vomiting should not be immediately offered more food, even if it is losing weight fast. If more food is given the vomiting will continue. Instead the bird should be allowed to settle for an hour then a small volume (0.5% of its body weight ie. 5ml per 1 Kg bird), of slightly warm (hand temperature) saline (eg. lectade) should be given by crop tube. The bird should be placed in a warm dark quiet area and allowed to settle. If the fluid is kept down, it should be repeated once more two hours later If that is retained then a further two hours later, a feed with the same volume of a liquidised food should be given by crop tube. Most standard cat and dog vets will stock suitable liquidised convalescent diets, examples are Hills a/d or Liquivite. The liquid food is repeated every 2 hours on 3-4 occasions, before the first meal of finely chopped beef (or similar). If the bird is not keen to take the meat, it Is not yet ready for it. As stated previously a bird may vomit for many reasons, from simple matters such as travel sickness, to more serious situations such as Aspergillosis. So unless the situation is truly straightforward, and the bird immediately responds, veterinary care should always be sought.
Feeding the Inappetant Bird - Frequently one is faced with a bird which is low in condition, which you know should be eating, which is however not wanting to feed. Many conditions can cause this. Any mouth (e.g. frounce, Capillaria, Candida), oesophagus/crop (e.g. local irritant, bacterial infection, sour crop, poxvirus), stomach (e.g. impaction, infection) or air sac (e.g. aspergillous, air sacculitis egg peritonitis) or septicaemia (eg. blood poisoning) condition will lead to a depressed appetite. Sometimes the bird will simply not eat, on other occasions the bird attempts to eat, but
then flicks its head all the time and brings the food back. Any such bird will need to be seen by a vet, an accurate and specific diagnosis made and the condition treated.
Bird which is Low in Weight, or not Putting Weight on in Relation to it's Food Intake - This situation is common. Either a bird may be taken out of an aviary after a moult and not be as heavy as it should be bearing in mind its ad libitum feeding, or the weight loss may be noticed as a consequence of daily weighing. Again a range of conditions may be responsible. The immediate reaction on the part of many keepers is to assume the bird is suffering a parasitic condition, Even if this is so, the keeper will probably then worm the bird with a standard wormer, such as Fenbendazole (Panacur). The problem is that such a wormer only treats one form of parasite (i.e. roundworms), so even if the problem is parasitic, the situation may go on unchecked. It is far more sensible to have a mute (faeces) sample checked, to see if it is a parasitic problem, and if so what is the correct medication to use. Furthermore if it is not parasitic one knows straight away, and can then take other action to find the real cause.
Weight loss may be caused by any illness. If it is gradual loss over a period of time the most likely causes will be parasites, bacterial gut infection, aspergillosis (even in the absence of any respiratory signed) or tuberculosis. Expert veterinary care is required, to differentiate and treat accordingly.
Feeding Birds and Travelling - Birds should not be fed directly before travelling, in particular if they are not used to travelling. If one is talking about an experienced flying bird, which is used to travelling, known not to suffer from travel sickness, then fair enough he may be fed up after a kill and allowed to travel home.
For a bird such as a Peregrine, we would advise giving a cast free meal 8-12 hours before travelling. The danger is that any bird with a stomach or crop full of food or casting, may regurgitate during the journey. This is particularly dangerous if the bird is hooded.
However, even without a hood, the bird can choke and die in a matter of a few seconds. Conversely a bird should not be starved for a long period before travelling. The smaller the bird, the less time they can manage without food. Many of the essential nutrients are not stored to any extent, or are unable to be rapidly mobilised, by the bird. Examples are glucose and calcium. Nervous birds, which are particularly sensitive to stress are prone to calcium deficient fits if food has been withheld and the bird is then stressed. In particular if goshawks are to be transported long distances (or undergo any other major stress), it is advised that they should be given additional calcium supplementation beforehand. In the author's experience the most effective product for this situation is 'Nutrobal' (Vetark). Even a single dose of this powder by mouth prior to such a situation is likely to be effective.
Casting in Adult Birds - This is a particular problem with chicks, but can present difficulties even in adult birds. If birds are tethered in mews, whose substrate is peat, wood shavings, or sawdust, then as the bird eats food, it the food has fallen on the ground, peat, wood shavings etc may also be ingested, leading to am impaction. Some adult birds will have difficulty in casting normal casting material, when it is fed to excess. Remember that in the wild, a bird will pluck much of its kill before ingestion. In captivity there may be more competition for food as birds in an aviary are obliged to eat in close proximity to other birds. The result may be a bird which 'pigs' its food down, ingesting excessive amounts of casting at the same time. In particular, breeding female birds should not have excessive casting. The reason being that their abdomen is currently unusually full of developing eggs as well as an enlarged oviduct. In either situation, having eaten the casting, birds may not be able to cast it. The consequence is that they continue to eat more casting, the pellet stuck in the stomach gets larger and larger, eventually forming a blockage.
Water - As previously stated, although raptors under normal daily conditions usually do not drink, when ill, stressed, in hot weather etc. they will often need to drink. With this in mind water should be available for birds on a daily basis, Care should be taken in
choosing a suitable water vessel as birds are able to drown themselves in even the shallowest container
Hawks. Hygiene and Eating - As previously stated, the hygiene of the food supply during its preparation, and the way and manner in which it is given is very important. However many falconers are blas¾ about their own hygiene when in the presence of their bird. We must accept that infections such as Salmonella enteridis are rife in the poultry industry, and hence will also be in day-old chicks. Likewise avian tuberculosis is common in feral birds. Either infection can be a serious pathogen to ourselves, so care should be taken. We are all prone, when short of a hand, to pull a gauntlet off with our teeth, temporarily forgetting who just got eaten on the fist, or who muted on it. Furthermore knives used in good preparation, as well as the occasional footing of your hand by your bird can introduce tetanus, which we all know is a dangerous and potentially fatal disease. Needless to say all falconers must have an up-to-date tetanus injection. Consult your own GIP, most advise a booster every ten years.
Calcium Deficiency in Adult Birds - As previously mentioned a diet should be varied and mixed, comprising of whole carcasses. However in display birds who are flying daily in front of the public and being fed up afterwards, whilst the spectators questions are being answered, this can be a problem. Understandably the public find a lump of meat far more acceptable than a fluffy chick or a rate. In this situation is is best to give just half a crop then feed up on rat etc. later. If meat is fed for any significant part of the daily food intake, they must also offset this deficiency by adding a calcium supplement such as 'Nutrobal' (Vetark).
Conclusion - There are risks involved in feeding almost any food to your birds. The main point is to be aware of the risks. Above all feed a varied diet, do not rely exclusively on 'day old' chicks, the diet must approximate as close as possible to the bird's diet in the wild. No bird in the wild feeds exclusively on chicks. Feed a hygienic, wholesome and varied diet, in that way you are more likely to keep a fit and healthy bird.
caring of BOP and their health
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