Commercial chickens

How does age of chickens (weeks) correlate to type?

What are the general causes of high mortalities in chicks?

Non-infectious causes

• Mangement issues —> temp/humidity/ventilation, water/feeding problems, transportation, hatchery issues (formaldehyde?), parent bird nutrition

• Nutritional deficiencies —> encephalomalacia, rickets

Infectious causes

• Navel/yolk sac infection —> Salmonella spp., E. coli etc.

• Aspergillosis

• Vaccine reactions (@ hatchery?)

• Avian encephalomyelitis

What are the main immunosuppressive diseases of growers and pullets?

• Infectious bursal disease virus

• Chicken anaemia virus

• Marek’s disease

• Reoviruses

• Mycotoxicosis – non-infectious

What are the resp dxs of growers & pullets?

• Mycoplasmas

• IBV

• aMPV/SHS

• ILT

• NDV

• AIV

• E coli

• P multocida (FC)

• Ornithobacterium  (ORT)

• Infectious Coryza

• Parasites – worm? Protozoa?

• Environmental?

What are the clinical signs of ORT? What are the main lesions PM?

• Coughing, sneezing

• Reduced weight gain, poor FCR

• Reduced egg production

• Main lesions – airsacculits, tracheitis, bronchopneumonia

How is ORT diagnosed, treated and prevented?

• Diag —> culture, PCR

• Tx —>ABs —> amoxicillin, chlortetracycline, macrolides

• Prevention —>Vaccine (autogenous), biosecurity, magenement improvements

What gastroenteric diseases affects growers and pullet?

• Salmonella

• E coli (ETEC)

• Clostridium

• Campylobacter

• Parasites - worms

• Parasites - protozoa

• Crop mycosis

What are the signs of clostridium enteritis infection?

• In any age but acute in young chickens

• Depression, ruffled feathers, sudden death, incr. mortality

• Subclinical —> weight gain, poor FCR.

What are the lesions associated with clostridium enteritis?

• Necrosis of intestinal mucosa

• Fibrinoectoric enteritis forming a diphtheritic membrane

• Mild form – focal necrosis of intestinal

What agent causes avian encephalomyelitis?

Picornavirus

What are the sings of avian encephalomyelitis?

• Tremor of head, neck & legs, paralysis, cataract

• Laying birds – drop in egg production

What is the diagnosis, treatment and prevention for avian encephalomyelitis?

• Diagnosis – histopathology, PCR

• Tx – none

• Prevention - vaccination

What are the non infectious causes of lameness in growers and pullets?

• Tibial dyschondroplasia

• Spondylolisthesis

• Rickets

• Valgus-Varus deformities (long bone distortion)

• Ionophore toxicity

What area does dyschondroplasia affect when causing lameness?

proximal tibiotarsus —> Tibial dyschondroplasia (TD)

What is dyschondroplasia influenced by?

• Genetic selection

• Feed: calcium/phosphorus ratios

• Acid:base balance in feed

• Mycotoxins

What causes rickets, how does it present, what is it influenced by?

• Calcium/Phosphorus or Vitamin D deficiency

• Rubbery ‘bones’

• Birds unable to support itself, increased skeletal deformities.

• Influenced by mycotoxins, malabsorption of Ca, P, vit D?

What are the infectious causes of lameness in growers and pullets?

• Marek’s disease

• Botulism

• Bumblefoot

• Viral arthritis

• Infectious synovitis

• Staphylococcus or other septic arthritis

List of the dxs affecting layers & main effect

What is the main agents causing egg peritonitis?

• Mostly E. coli

  • Secondary to M. synoviae, P. multocida, Erysipelas, ORT

  • IBV, aMPV, NDV, AIV

What are the influencing factors of peritonitis in layers?

• Flock uniformity

• Body weight

• Physical and hormonal stresses

• Source of bacteria, e.g. water & air

How is peritonitis in layers prevented?

• Sustain body weight & uniformity

• Reduce stress factors

• Minimise bacterial challenges

• Control the primary pathogens via vaccination

• Vacc against E. coli

How is peritonitis treated?

• AM therapy

• E.coli vacc

What are the different species of Brachyspira affecting layers and what severity of disease do they cause?

• B. innocens – little or no disease

• B. pilosicoli – mild disease

• B. alvinipulli - mild disease

• B. intermedia – severe disease

production losses?

How is a brachyspira infection diagnosed?

• Appearance of faeces

  

• Confirmed by culture and PCR

How is brachyspira infection prevented & treated?

• Organic acid programmes

• Macrolides

What is the causative agent of egg drop syndrome?

Adenovirus

What are the signs of egg drop syndrome?

• 5-50% drop in 3-4 weeks

• Shell quality may or may not be affected

• No incr. mortality

• Lesions —> none specific, ovary/oviduct dystrophy

How is egg drop syndrome diagnosed, treated and prevented?

Diag: serology, histopath, PCR

Tx: none, supportive

Prev: vacc (inactivated)

Example vaccines and ROAs for reference

CAV = chicken anaemia virus

AE = avian encephalomyelitis

IBDV = infectious bursal dx

MS = mycoplasma synoviae

EDS = egg drop syndrome