Poultry Flashcards
Outline the approach to lameness in poultry
- 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
How many birds should be blood samples be taken from in order to confirm
a: infection, b: vaccination responses, c: diagnosis
a: 60
b: 20-30
c: 10-20
What are the broad categories of differentials for lameness in poultry?
- Viral
- Bacterial
- Parasitic
- Nutritional
- Genetic
- Metabolic
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?
- Spondylolisthesis (kinky back): can feel deformity at level of free vertebrae, radiography for diagnosis
- Osteomyelitis of thoracic spine: radiography
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
- Rickets
- Tibial dyschondroplasia
Describe the normal appearance of the avian pelvic acetabulum
Deep, perforated in centre (not a solid cup)
Describe the normal anatomy of the avian pelvis
- Pelvis (= ischium, ilium, pubis) fused to synsacrum at ilium
- Open ventrally
- Trochanter of femur articulates with antitrochanter of pelvis
- More running = wider pelvis
Describe the normal anatomy of the avian femur
- 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
What group of birds have a particularly large patella?
Aquatic birds
Describe the anatomy of the tibiotarsus of birds
- 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)
Describe the anatomy of the avian tarsometatarsus
- 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
Name the extensors of the hip in birds
- Pubo-ischio-femoralis
- Iliofemoralis
Name the flexor of the hip in birds
Iliotibialis cranialis
Describe the normal movement of the hip in birds
- Extends and flexes, also rotation in recovery phase
- Very little abduction/adduction
Name the flexor and extensor of the stifle in birds
- Flexor: iliofibularis
- Extensor: femorotibialis
Name the flexor and extensor of the hock in birds
- Flexor: tibialis cranialis
- Extensor: gastrocnemus
Describe the path and common disease of the gastrocnemus tendon in birds
- Passes through sleeve connected to caudal surface of cartilage, ends on plantar aspect of tarsometatarsus
- Heavy birds often develop slipped tendon
Describe the movements of the digits in birds
- Flex and extend
- Abduct and adduct
What is the function of the flexor tendons of the digits in birds?
- Allow perching
- Also locking mechanism: flexor tendon ratchet that prevents moving when muscle tensed and toes are flexed and gripping
Describe the pathophysiology of rickets in birds
- Thickening of all long bone growth plates
- Long bones are soft and pliable
- May get rickets rosaries
What causes rickets in birds?
Lack of vit D3 or Ca/P imbalance resulting in lack of mineralisation
How is rickets confirmed in birds?
Histopathology
What is tibial dyschondroplasia in birds?
Thickening of growth plate in tibiotarsal bone
Describe the patholophysiology of tibial dyschondroplasia in birds
- 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
Describe the clinical signs of tibial dyschondroplasia in birds
- Abnormal gait progressing to lameness
- Frequently laying down
- Reluctance to stand
- Decreased movement
- Depression
Identify the risk factors for tibial dyschondroplasia in birds
- Young, rapidly growing male broiler chicks 3-8wo
- Mycotoxin contamated feed
- Faster growing chicken breeds
- Unbalanced diet: too little calcium, too much phosphorous
How is tibial dyschondroplasia in birds diagnosed?
- History
- Clinical signs
- Physical examination
- Radiography
Outline the treatment for tibial dyschondroplasia in birds
- Supportive care only e.g. sling, correct nutritional imbalance
- Mainly prevention in as yet unaffected members of flock
Outline the pathophysiology of chondrodystrophy in birds
- 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
Outline the aetiology of chrondrodystrophy in birds
Nutritional, or secondary to congenital infection, but very uncommon
Describe the clinical signs of femoral head necrosis in birds
- 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
Outline the diagnosis of femoral head necrosis in birds
- Histopath showing disintegration of proximal femur
- Need histology to rule out agonal change
- Confirmation of causal agent by C+S or serology
List the potential aetiologies of femoral head necrosis in birds
- Immunosuppression
- Bacteria e.g. S. aureus
- Reovirus
Which birds are typically affected by hock infections?
- Larger birds
- Just prior to slaughter
Outline the clinical signs of hock infections in birds
- Lame initially
- Swollen, inflamed footpads and hocks
- Lethargy
- Breast blisters
- Ruffled feathers
- Shriveled, shrunken, pale comb or red-blue comb
Discuss the cause of hock infections in birds
- Poor hygiene
- Possible organisms: S. aureus, E. coli, Ornithobacterium rhinotrcheale, Mycoplasma synoviae
Outline the treatment/management of hock infections in birds
- Antibiotics (based on sensitivity) in early lesions
- Supportive care
- Reduction of rodent population to reduce incidence
Describe the clinical signs of tendon rupture in birds
- Hopping lame
- palpable thickening of gastrocnemius tendon above hock joint
- Associated with rapid growth and insufficient exercise
Which birds are predisposed to spondylolisthesis?
Females, heavy meat-type chickens
Describe the pathophysiology of spondylolisthesis
- 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
Describe the clinical signs of spondylolisthesis (kinky back) in chickens
- 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
Outline the treatment of spondylolisthesis in chickens
Supportive care possible, but generally cull
Outline general preventative measures to reduce lameness in poultry
- Vaccines (Marek’s, Gumboro etc.)
- Diet changes
- Water supplementation
- Stocking levels
- Breed changes
- Husbandry alterations (e.g. bedding substrate, ventilation)
- Kill schedule
How may Marek’s disease present?
- Often presented as sudden death, wing and legs outstretched
- Can present as intermittent paralysis/lameness
