See also: 

• Food and Feeding for Birds - Convalescent Diets / Nutritional Support
• Wildlife Casualty & Convalescent Feeding (with special reference to UK Wildlife)
• Treatment and Care - Fluid Therapy

• All the equipment and consumables required should be prepared and placed ready for use before the bird is removed from its accommodation.
• A clean, sterilised tube should be used for each individual bird.
• Check that the tube is patent (not blocked) before use; with transparent tubes a visual inspection can be used.
• Prepare a syringe with the required medication, fluids or formula.
• Connect a flexible feeding tube (for example: a urinary catheter, giving set, lamb feeding tube or stainless steel feeding needle) firmly to the syringe ensuring that the tube is of a type that will not cause damage to the mucosa, with a smooth and rounded end.
  • Note that the end of the syringe must fit the tube used, e.g. a catheter-tipped syringe is required to fit a lamb feeding tube. (B13.15.w10)
• If tube feeding or giving fluids, check the temperature of the feed/fluids (should be warm but not too hot) - squirt a small amount onto your wrist to check the temperature. (D9)
• Fluids may be warmed by placing them in hot water until they are just warm to the touch (100°F/38°C). (D135.5.w5)
• Empty the tube of air by expelling a little fluid from the syringe. (D135.5.w5)

Volumes for rehydration or feeding:

The volume of fluids or food mixture which may be given at one time by gavage is limited. Different authorities suggest different limits:

• Recent publications from oiled wildlife responders in the USA suggest that 50 mL may be given per kg body weight (i.e. about 5% of body weight), although smaller volumes should be given initially, for example only half this volume, with the amount increased from 2.5% of body weight (25 mL/kg) to 5% of body weight (50 mL/kg bodyweight) gradually over several gavages. (D133.5.w5, J29.7.w1)
• In recent Australian publications it has been suggested that most birds can accept about 10 - 20 mL per kg bodyweight at one time, the smaller volume for birds without a crop and the larger volume for birds with a crop; for most seabirds it is suggested that 15 - 30 mL can be given per kg bodyweight. (B363.App5.w18, P24.327.w4) 
• A British publication gives the following "Rule of Thumb": maximum up to 2% of bodyweight at one time. Generally assume 1 ml of liquid to weigh 1 gram, therefore give up to 2 ml per 100g bodyweight, i.e. 20 ml per kg bodyweight. (B156.15.w15)
• A recent chapter on seabirds in another European publication suggested that for gavage feeding, up to 30% body weight could be given in up to four feeds daily, but stated that "it is rare to force feed more than 20% body weight in two feeds." (B197.15.w15)
• Examples have also been given:
  • Canary, finch: 0.25-0.5ml
  • Budgerigar: 1.0-1.5ml
  • Cockatiel: 2-3ml
  • Small parrot: 5-8ml
  • Medium to large parrot: 8-12ml
  • Large cockatoo: 10-15ml
  • Medium to large macaw: 15-30ml
  • Mallard duck: 60ml
  • Mute swan: 120ml
  • Adult crane: 150ml maximum, start with 60-80ml
  • Crane chick (hatchling): 3ml
  • (B13.15.w10, B37.x.w1, B115.5, B115.8, B119.w3, B197.11.w11)
  • 7.5 ml for common gull or kittiwake. (D141)
  • 3.75 ml for black-headed gull, little gull. (D141)
  • 15 ml for a Uria aalge - Common murre (Common guillemot), Alca torda - Razorbill. (D139), Lesser black backed gull, Herring gull. (D141)
  • 22.5 ml for Greater black backed gull. (D141)
  • 45 ml for a gannet Morus bassanus - Northern gannet or cormorant Phalacrocorax carbo - Great cormorant. (D140)
  • 30 ml for a shag (Phalacocorax aristotelis - European Shag). (D140)
  • For further examples of volumes for different sea bird species see: D133 - Protocols for the Care of Oil-Affected Birds - Appendix 14 - full text provided

Gavage:

• Restrain the bird’s body and head, holding the bird in a vertical position with the neck extended.
  • One person can hold the bird while a second person carries out the procedure.
  • Experienced personnel may be able to carry out gavage single-handed, particularly for smaller birds. (B13.15.w10)
  • With large, aggressive birds, particularly piscivorous (fish eating) birds, goggles should be worn to protect the eyes. (V.w5)
• Externally measure the distance from the mouth to the intended delivery site (crop or stomach). Determine how much of the catheter (tube) should still be exposed once the tip has reached the crop (base of the neck). (D135.5.w5)
• Palpate the crop to ensure that it is empty before giving food by gavage. (B13.15.w10)
• Apply gentle pressure at the commisures of the bill and open the bill. (D9)
  • An oral speculum may be useful for some species such as large psittacines (Psittacidae - Parrots and allies (Family)). This must be used with care to avoid damaging soft tissues. (B13.15.w10)
• Apply gentle pressure to stabilize the tongue.
• Extend the bird's neck upwards and forwards. (D135.5.w5)
• Visualise the glottis (opening to the trachea) at the base of the tongue. (D9)
  • The feeding tube must NOT be placed into the glottis.
• Bring the tube in from the left oral commissure, moving it backwards and across the mouth, past and to the right of the glottis, sliding it into and down the oesophagus on the right side of the neck and to the crop or stomach. (D9)
• Confirm the tube is in the oesophagus/crop by visual inspection and/or gentle palpation of the neck. (D9)
  • It should be possible to see that the tube goes down behind the glottis. (D9, D135.5.w5, V.w5)
  • A slight bulge should be visible/palpable in the neck; the end of this should move if you move the tube up and down slightly. (D135.5.w5)
  • Damping the feathers on the right side of the neck may assist in visualising the tube. (B13.15.w10)
  • Note: Particular care is required to ensure that the feeding tube has been properly positioned into the oesophagus, when tube-feeding long-billed birds. (B336.16.w16)
• Slowly deliver the fluids or feed formula, monitoring for fluid appearing in pharynx. Stop if this occurs, and continue at slower rate. (D9)
  • If the bird regurgitates it should be released  to allow it to clear its oral cavity. (B13.15.w10, D9)
    • The bird should be allowed to shake its head and neck if food is being regurgitated. (D135.5.w5)
• When the syringe is empty, pinch or fold over the tube and remove it quickly. (D9)
  • Stop just before the syringe is empty, to avoid pushing air into the gastrointestinal tract. (D135.5.w5)
  • The tube is pinched or folded over to prevent dripping and possible aspiration of fluid/food. (D135.5.w5)

Post-gavage:

• Keep the bird's head extended while returning it to its accommodation. (B13.15.w10)
• Avoid disturbing the bird for at least 20-30 minutes to reduce the risk of regurgitation.

• Tube feeding is an excellent way to initially improve gastrointestinal motility in a debilitated animal, and provide longer term hydration and nutrition.
• Definitive amounts of medication can be administered.
• Medication can be delivered directly to crop or stomach.
• Fluid medications often are more readily absorbed.
• Effective for routine administration of fluids to mildly dehydrated individuals.

• The tube touching the roof of the mouth and passing slowly over the base of the tongue should stimulate reflex closure of glottis. (J2.12.w3)
• If used for providing nutrition in a bird which is not taking food voluntarily, careful calculation of nutrients being provided is essential to ensure that sufficient nutrition is being provided to meet the bird's needs..
• A gag and/or metal tube is required for species with a strong beak and good cutting edges , such as psittacines (Psittacidae - Parrots and allies (Family)), to prevent the bird from biting down, severing the tube and swallowing the free end.
• Check patency of tube before each use.
• Cleaning followed by sterilisation in Milton for 30 minutes (D139) or another sterilisation fluid is required if a tube is to be reused. (D139)

• This route of fluid administration is not effective in severely dehydrated or severely debilitated individuals.
  • There is an increased risk of regurgitation and aspiration.
  • Such individuals have reduced absorption from the gastro-intestinal tract.
  • Parenteral fluids (intravenous or intraosseous) are preferable in such cases.
• Not suitable for use if the individual is vomiting or has reduced gastro-intestinal tract mobility.
• Not suitable if the individual is unable to maintain its head carriage normally as there is an increased risk of regurgitation and aspiration.
• There is always a risk of damage to the mucosa.
• Extra care is required to avoid perforating the oesophagus if a metal crop tube is used.
• In birds with sharp edges to the bill care must be taken that the bill does not close onto a non-metal tube and cut it, allowing the tube to be swallowed.
• There is a risk of improper tube placement, into the trachea, and delivery of fluids/food/medication into the lungs, often with fatal results.
  • Particular care is required to ensure that the feeding tube has been properly positioned into the oesophagus, when tube-feeding long-billed birds. (B336.16.w16)
• Risk of regurgitation and aspiration. N.B. vomiting/regurgitation is more likely if the food is cold rather than warmed.
• Overheating of fluids or food mixtures must be avoided. Take care to ensure food does not contain "hotspots" which may burn the bird's internal tissues, particularly if the feed has been heated in a microwave - also note that feed continues to heat after leaving the microwave. (D9)
• Fluids or food mixtures which are too hot can scald the oesophagus and crop. (D135.5.w5)
• If too cold a mixture is used, regurgitation is more likely. (D9)
• Tube may become blocked.
  • Feed mixtures made from e.g. ground up pellets often swell after being mixed with water. Care must be taken that the mixture is sufficiently thin to pass through the tube.
• Limited to individuals or small groups or animals.
• Often more than one individual is needed to accomplish the procedure.
• Only a limited volume of fluids/food can be delivered at one time.
• Parasitism, diseased mucosa and nutritional deficiencies such as Vitamin A Deficiency may adversely affect absorption of drugs given by this route.
• Not all drugs are absorbed if given orally.
• If tubes are not properly cleaned and sterilised between birds then pathogens may be transmitted from one bird to another.

• Appropriate sized tube, e.g. 0.5 to 1.0 cm diameter in waterfowl, of correct length.
• Syringes of appropriate sizes and with the correct tip to fit the tubes to be used.
• Appropriate fluids, liquefied / suspended food or medication.
• Sterilising solution if tubes are to be used with more than one bird. 
• Gag if appropriate (e.g. for large psittacines (Psittacidae - Parrots and allies (Family))).

• Procedure should only be undertaken by an individual with appropriate clinical training and practical experience.
  • Application of the procedure single-handed (same person holding the bird and carrying out gavage) should only be used by persons who are familiar with both handling birds and carrying out gavage. 

• Not generally expensive, unless expensive medication / food / fluids are being given.

Use of Drugs (Medication):

• Many drugs are not registered for use in particular bird species and care should be taken in their use, with proper regard for possible toxic effects. Consideration should be give to relevant legislation regarding the use of drugs.
• In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons Guide to Professional Conduct 2000: (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).