Poultry

Question 1

Outline the approach to lameness in poultry

Answer 1

• Establish “normals”
• Establish history
• PM investigation
• Testing: blood, histology, faecal microscopy, gut content microscopy, electron microscopy, virus isolation, PCR
• Culling of severe cases of lameness

Question 2

How many birds should be blood samples be taken from in order to confirm
a: infection, b: vaccination responses, c: diagnosis

Answer 2

a: 60
b: 20-30
c: 10-20

Question 3

What are the broad categories of differentials for lameness in poultry?

Answer 3

• Viral
• Bacterial
• Parasitic
• Nutritional
• Genetic
• Metabolic

Question 4

What are the differentials for a bird presented with sitting on the hocks, no obvious leg lesions and no obvious pain? How are these diagnosed?

Answer 4

• Spondylolisthesis (kinky back): can feel deformity at level of free vertebrae, radiography for diagnosis
• Osteomyelitis of thoracic spine: radiography

Question 5

What are the differentials for a bird presented with: uncomfortable walking, bilateral lameness, thickened bones of hock, mild bone deformities present, malleable bones and beak

Answer 5

• Rickets

- Tibial dyschondroplasia

Question 6

Describe the normal appearance of the avian pelvic acetabulum

Answer 6

Deep, perforated in centre (not a solid cup)

Question 7

Describe the normal anatomy of the avian pelvis

Answer 7

• Pelvis (= ischium, ilium, pubis) fused to synsacrum at ilium
• Open ventrally
• Trochanter of femur articulates with antitrochanter of pelvis
• More running = wider pelvis

Question 8

Describe the normal anatomy of the avian femur

Answer 8

• Directed cranially as goes distally
• Femoral condyles attached by ligaments to tibiotarsus and head of fibula
• Femorotibial joint similar to mammalian stifle: 2 menisci, 2 cruciate ligaments, lateral/medial collateral ligaments

Question 9

What group of birds have a particularly large patella?

Answer 9

Aquatic birds

Question 10

Describe the anatomy of the tibiotarsus of birds

Answer 10

• Tibiotarsus formed by fusion of tibia and proximal row of tarsal bones
• Fibula attached to tibiotarsus by tight fibrinous union at fibular crest
• Hock is intertarsal between tibiotarsus and tarsometatarsus (single meniscus, single cruciate)

Question 11

Describe the anatomy of the avian tarsometatarsus

Answer 11

• Fusion of distal tarsal bones to 3 main metatarsal bones
• Extends to the ground
• Hypotarsus is a groove on plantar aspect of tarsometatarsus through which the digital flexor tendons pass

Question 12

Name the extensors of the hip in birds

Answer 12

• Pubo-ischio-femoralis

- Iliofemoralis

Question 13

Name the flexor of the hip in birds

Answer 13

Iliotibialis cranialis

Question 14

Describe the normal movement of the hip in birds

Answer 14

• Extends and flexes, also rotation in recovery phase

- Very little abduction/adduction

Question 15

Name the flexor and extensor of the stifle in birds

Answer 15

• Flexor: iliofibularis

- Extensor: femorotibialis

Question 16

Name the flexor and extensor of the hock in birds

Answer 16

• Flexor: tibialis cranialis

- Extensor: gastrocnemus

Question 17

Describe the path and common disease of the gastrocnemus tendon in birds

Answer 17

• Passes through sleeve connected to caudal surface of cartilage, ends on plantar aspect of tarsometatarsus
• Heavy birds often develop slipped tendon

Question 18

Describe the movements of the digits in birds

Answer 18

• Flex and extend

- Abduct and adduct

Question 19

What is the function of the flexor tendons of the digits in birds?

Answer 19

• Allow perching

- Also locking mechanism: flexor tendon ratchet that prevents moving when muscle tensed and toes are flexed and gripping

Question 20

Describe the pathophysiology of rickets in birds

Answer 20

• Thickening of all long bone growth plates
• Long bones are soft and pliable
• May get rickets rosaries

Question 21

What causes rickets in birds?

Answer 21

Lack of vit D3 or Ca/P imbalance resulting in lack of mineralisation

Question 22

How is rickets confirmed in birds?

Answer 22

Histopathology

Question 23

What is tibial dyschondroplasia in birds?

Answer 23

Thickening of growth plate in tibiotarsal bone

Question 24

Describe the patholophysiology of tibial dyschondroplasia in birds

Answer 24

• Zone of hypertrophied cartilage cells in proximal end of tibiotarsal bone fails to become callcified because blood supply is absent i.e. stays soft
• Commonly leads to leg fractures, necrosis, severe pain, lameness

Question 25

Describe the clinical signs of tibial dyschondroplasia in birds

Answer 25

- Abnormal gait progressing to lameness - Frequently laying down - Reluctance to stand - Decreased movement - Depression

Question 26

Identify the risk factors for tibial dyschondroplasia in birds

Answer 26

- Young, rapidly growing male broiler chicks 3-8wo - Mycotoxin contamated feed - Faster growing chicken breeds - Unbalanced diet: too little calcium, too much phosphorous

Question 27

How is tibial dyschondroplasia in birds diagnosed?

Answer 27

- History - Clinical signs - Physical examination - Radiography

Question 28

Outline the treatment for tibial dyschondroplasia in birds

Answer 28

- Supportive care only e.g. sling, correct nutritional imbalance - Mainly prevention in as yet unaffected members of flock

Question 29

Outline the pathophysiology of chondrodystrophy in birds

Answer 29

- Insufficient bone produced at cartilaginous growth zone, resulting in short bowed bones - Appositional growth (normal) leading to swollen joint appearance - May predispose to slipped tendons

Question 30

Outline the aetiology of chrondrodystrophy in birds

Answer 30

Nutritional, or secondary to congenital infection, but very uncommon

Question 31

Describe the clinical signs of femoral head necrosis in birds

Answer 31

- Severely lame - Difficulty rising, wings used for support - Possible pain on palpation on medial aspect of femur - Severely lame - Hot swollen joints and/or tendons

Question 32

Outline the diagnosis of femoral head necrosis in birds

Answer 32

- Histopath showing disintegration of proximal femur - Need histology to rule out agonal change - Confirmation of causal agent by C+S or serology

Question 33

List the potential aetiologies of femoral head necrosis in birds

Answer 33

- Immunosuppression - Bacteria e.g. S. aureus - Reovirus

Question 34

Which birds are typically affected by hock infections?

Answer 34

- Larger birds | - Just prior to slaughter

Question 35

Outline the clinical signs of hock infections in birds

Answer 35

- Lame initially - Swollen, inflamed footpads and hocks - Lethargy - Breast blisters - Ruffled feathers - Shriveled, shrunken, pale comb or red-blue comb

Question 36

Discuss the cause of hock infections in birds

Answer 36

- Poor hygiene | - Possible organisms: S. aureus, E. coli, Ornithobacterium rhinotrcheale, Mycoplasma synoviae

Question 37

Outline the treatment/management of hock infections in birds

Answer 37

- Antibiotics (based on sensitivity) in early lesions - Supportive care - Reduction of rodent population to reduce incidence

Question 38

Describe the clinical signs of tendon rupture in birds

Answer 38

- Hopping lame - palpable thickening of gastrocnemius tendon above hock joint - Associated with rapid growth and insufficient exercise

Question 39

Which birds are predisposed to spondylolisthesis?

Answer 39

Females, heavy meat-type chickens

Question 40

Describe the pathophysiology of spondylolisthesis

Answer 40

- Ventral dislocation of anterior end of the articulating 4th thoracic vertebra, rotates the posterior end causing it to pinch the spinal cord - Damage to spinal cord result in onset of partial posterior paralysis in the chicken

Question 41

Describe the clinical signs of spondylolisthesis (kinky back) in chickens

Answer 41

- Arched back - Sitting on tail, feet extended outward/or feet falling to one side of body - Neck extending outwards - Wings used when walking - Walking backwards - Falling sideways

Question 42

Outline the treatment of spondylolisthesis in chickens

Answer 42

Supportive care possible, but generally cull

Question 43

Outline general preventative measures to reduce lameness in poultry

Answer 43

- Vaccines (Marek's, Gumboro etc.) - Diet changes - Water supplementation - Stocking levels - Breed changes - Husbandry alterations (e.g. bedding substrate, ventilation) - Kill schedule

Question 44

How may Marek's disease present?

Answer 44

- Often presented as sudden death, wing and legs outstretched - Can present as intermittent paralysis/lameness