Broiler disease investigation – understanding the process 

broilers in a shed by feeder pans

Disease in broilers can quickly undermine profitability. 

When a problem arises, understanding investigative protocols can help with swift diagnosis and treatment. Aaron Finucane reports. 

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Managing disease challenges is key to maintaining a healthy flock and a healthy balance sheet. 

Hannah Lock, vet at Poultry Health Services

But recognising an issue is only the first step in diagnosis. So, what else do farmers need to know?

Firstly, producers should understand the performance guidelines outlined by their flocks’ genetics supplier, explains Hannah Lock, a vet at Poultry Health Services. “Deviation from those guidelines – either positive or negative – warrants investigation.”

If disease is suspected, the next step is reaching a diagnosis and implementing a plan to tackle it. “Producers can speed up this process by understanding protocols like what birds or samples to submit for testing.”

Production impacts

The impact of disease on production and profitability is multifactorial, says Dr Lock. “Prompt diagnosis and treatment to control spread among a flock, as well as other farm sites, is key to limiting production and financial losses.

“If diagnosis and clinical resolution is delayed, it can restrict the flock’s growth potential and reduce treatment options. Early consultation with a vet and submitting the right birds for investigation is imperative.”

Signs and symptoms

As birds move through their lifecycle, clinical symptoms and guidelines for assessing a problem can change, says Dr Lock. “Among young chicks, producers should look out for lower-than-expected feed and water intakes, reduced activity, and mortality over 0.5% in a single day.

“As chicks grow, an additional key indicator is lameness, which is often linked to infections. Mortality levels should still be considered, with anything over 1% per week requiring investigation.

Litter quality

“The third indication of disease presence is compromised gut integrity. 

Farmers may see wet litter and reduced growth rates caused by dysbacteriosis (disruption of the gut microbiome), with coccidiosis or bacterial infection often being to blame.”

Submission and testing

It’s vital for producers to work with vets at this stage, and to understand what information they need.

“The cornerstone of poultry diagnostics is post-mortem (PM) examination,” says Dr Lock. “Often, it’s farmers who submit those birds, and the process for selecting them is quite important. 

“We need a representative sample of those experiencing clinical symptoms, so if lameness is the problem, supply lame birds.”

Criteria for selecting birds:

  • Select birds that are symptomatic
  • Avoid birds that are not representative of the flock (poorly grown)
  • Birds that have died naturally need to be fresh
  • If increased mortality due to death is the issue, submit mainly birds that have died naturally and a sample of symptomatic cull birds
  • If increased mortality due to culling is the issue, submit mainly cull birds
  • If multiple sheds are affected, supply birds from each of the different sheds with a clear label in the bag identifying the shed number
  • Vets need information about the number of birds affected by symptoms, the number of deaths and culls, feed and water intake data, plus their general well-being, site history and treatments given

Once a PM is concluded, vets can order relevant laboratory tests to confirm or rule out the presence of infection. 

Results are generally quick (some can be available on the same day, some the day after) and, combined with clinical history, are often useful in reaching a diagnosis.

But the diagnostic arsenal includes other tools, like polymerase chain reaction (PCR) or blood testing, explains Dr Lock. 

Representative sample

“The protocol for submitting birds is similar to that for PM. We want a representative sample of live (for blood tests) birds that are symptomatic, and from multiple sheds if more than one flock is affected. 

“With these tests, we can diagnose respiratory diseases like mycoplasma.

“And we have other routine testing options like faecal egg sampling for coccidiosis or other parasites, and routine water testing to identify pathogenic contamination.”

Bird flu

Avian influenza (AI) is currently a significant issue for UK production. 

Submitting birds for testing at the right time can influence diagnosis speed, and therefore compensation levels, says Dr Lock. “Mortality which doubles day-on-day is the major red flag in relation to AI. 

“But clinical symptoms can otherwise be ambiguous. When a producer contacts their vet, screening questions will be asked; if AI is suspected then birds should not be moved off the holding. Your vet will advise on the protocol for diagnosis and submitting birds for testing. 

Diagnosis vs prevention

While diagnosis will always have its place, preventative testing and medicine is the future, explains Dr Lock. 

“It’s about pre-empting issues. Preventative medicine and monitoring, like routine environmental testing and prophylactic supplementation based on site-specific backgrounds, can help us prevent or identify and treat issues early.

“Identifying an active issue in a flock requires well-understood diagnostic procedures, but even under those circumstances’ outcomes can still be costly. Preventative monitoring and interventions tend to lead to more beneficial outcomes.”