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Pigeon Limb Deformity
There have been a
few articles and questions concerning splayed-legs and crooked toe abnormalities
in pigeons in the APJ recently. We've accumulated some information from sources
and compiled them together to hopefully stimulate thought on the etiology (cause)
of these diseases. A brief description of the abnormality is given. Pathogenesis
refers to the development of the disease process.
Crooked Toes
Description: Crooked toes is a condition best described in poultry as a developmental
anomaly in which the toes are bent laterally and medially (outward and inward, respectively)
in a horizontal plane. This is different than curled toes in pigeons and poultry
which is due to a riboflavin deficiency in the diet.1,2
Pathogenesis: Crooked toes occurs due to a twisting of the phalanges (toe bones).
Etiology: The cause is unknown, however wire floors and low humidity may predispose
birds to the anomaly. The greater incidence in different pigeon breeds suggests
a genetic problem or management situation particular to that breed (e.g. crooked
toes in Domestic Flights).
Rotated Tarsometatarsus
Description: This is a deformity of the lower leg, past the hock joint, in which
the tarsometatarsal bone rotates laterally or medially.
Pathogenesis: It is associated with twisting and bending of the lower tibiotarsal
and upper tarsometatarsal bones (above and below the hock joint).3
Etiology: The cause is unknown but may be secondary to perosis (slipped tendon)
and not a primary disease.
Perosis
Description: Perosis is enlargement of the hock joint and rotation of the tarsometatarsus
due to slipping of the Achilles' tendon.
Pathogenesis: The tendon of the gastrocnemius muscle (Achilles' tendon) slips laterally
(towards the outer side) of the hock and there is shortening of the bones of the
affected leg due to changes in the growth plate.1,3
Etiology: Manganese deficiency, choline deficiency, biotin and pantothenic acid
deficiency, calcium/phosphorus/Vitamin D imbalance, niacin deficiency, Vitamin B6
and folic acid deficiency are all causes of perosis in poultry and waterfowl.
Twisted Leg
Description: An outward or inward twisting and bending of the leg; usually only
one leg is affected.1
Pathogenesis: Slipped tendon of gastrocnemius muscle.
Etiology: The incidence of affected individuals is increased in some flocks; suggesting
a genetic influence. The nutritional causes of perosis should also be considered.
The use of improper or insufficient nesting material or nesting containers is mentioned
by Levi (columbids) and by Voren and Jordan (psittacines)4,5 The cause is most likely
multifactorial and not limited to just one etiology, but rather may be a combination
of disease syndromes.
Angular limb deformities in pigeons are always difficult to treat and cure in older
youngsters, however, if caught early, squeakers can be treated with amazing results.
John Hanson's "15 cent Solution" in July, 1992 APJ issue is an effective,
innovative method to control splayed legs.6 Notice that the squabs he is treating
by placing two leg bands with an interconnecting elastic band are young birds that
can still be banded. This is the key to success, catch 'em early!
Anne Ellis's April 1992 APJ article gives an excellent alternative. She utilizes
a bread tin to keep the legs held beneath the body and prevent splaying. She too
is still treating birds that are young and still growing, otherwise they would flap
their wings and work their way out of the bread tin. Both these methods are a variation
on another theme. The goal is to provide a substrate or apparatus to prevent the
legs from splaying out. Many methods can accomplish this. Bowls and tins which
restrict outward leg movement are readily available and inexpensive. Deep, coarse
and heavy nest material such as alfalfa pellets covered with a more natural layer
of nest material may also help.
Another method is to use external fixation splints. An apparatus that extends from
one limb to the other is often effective but can be fraught with frustration. The
key is to keep it simple. Bulky tapes and appliances attached to the legs often
hinder the bird, can lead to two deformed limbs, cause soiled plumage and may result
in painful sores. John Hanson's method is effective as long as the leg bands do
not ride up near the hock but remain near the feet.
The last and least desirable method is reserved for special situations and involves
surgery. A derotational osteotomy in which the bone is cut and the leg de-rotated
is seldom effective and used as a salvage procedure to give the bird a better quality
of life. The Achilles' tendon usually remains slipped and thus the lower leg is
barely functional. Unless the bird is a pet or has an otherwise high inherent value,
culling is recommended.
A proverbial ounce of prevention is definitely worth a pound of cure. Unfortunately,
it is difficult to prevent what is not clearly understood. The only recommendations
to make are the obvious: provide adequate nutrition, vitamins, nest material and
nest bowls to your birds. Until the etiology of angular limb deformities can be
elucidated, it is recommended these birds be eliminated from the breeding population.
Vitamin D is necessary for metabolism of calcium and phosphorous and for absorption
of calcium from the diet. Deficiency causes weak bones, enlargement of joints and
soft-shelled eggs. Excess vitamin D may cause severe kidney damage and calcified
tissues.
Calcium is needed for bone and eggshell formation. Deficiency causes soft-shelled,
weakness, paralysis, soft bones and egg binding. Excess dietary calcium without
increasing dietary phosphorous causes kidney damage and mineralized tissues.
Phosphorous is essential for proper calcium metabolism. Calcium and phosphorous
should be balanced in the ration to a ratio of 1.5:1 for young birds and 2.5-1 for
breeding birds.
Niacin is necessary to prevent bowing of the legs and enlargement of the hocks.
A deficiency does not usually cause perosis.
Manganese prevents enlargement of the hock joint and prevents tendon slippage of
the gastrocnemius muscle.
Zinc deficiency may result in shortened and thickened long bones, enlarged hocks
and weakness. An excess is usually caused by ingestion of zinc from cage/wire clippings
and may cause gastrointestinal and neurologic signs.
Choline deficiency also may result in perosis and cartilage deformities in joints.
Biotin is necessary to prevent shortening of leg bones in embryos and perosis.
References
1. Fraser CM (ed): Part VI, Diseases of Poultry. In Merck Veterinary
Manual 6th ed. Rahway, NJ, Merck & Co., Inc., 1986, pp 1301-1302.
2. Tudor DC: Pigeon Health and Disease. Ames, IA, IA St. Univ. Press, 1991, pp
117-134.
3. Altman RB: Disorders of the Skeletal System. In Petrak ML (ed), Diseases
of Cage and Aviary Birds 2nd ed. Philadelphia, Lea & Febiger, 1982, pp 382-394.
4. Levi WM: The Pigeon. Sumter, SC, Levi Pub. Co., Inc., 1977, p 408.
5. Voren H and Jordan R: Parrots, Hand Feeding and Nursery Management. Pickering,
Ontario, Canada, Silvio Mattachione & Co., 1992, pp 150-151.
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