Chicken Respiratory Disease: Welfare in Broiler and Layer Flocks

How infectious bronchitis, Newcastle disease and other respiratory pathogens affect poultry welfare and flock-level management.

Key Facts

Respiratory disease accounts for approximately 30% of all poultry mortality and condemns in commercial production
Infectious bronchitis virus (IBV) is the most economically significant respiratory pathogen in commercial layer flocks
Newcastle disease virus can kill 100% of an unvaccinated flock within days — a catastrophic welfare and production event
Poor ventilation, overcrowding and inadequate litter management dramatically increase respiratory pathogen transmission
Subclinical respiratory infection causes chronic respiratory discomfort without obvious signs — flock-level welfare is compromised
Mycoplasma gallisepticum causes air sacculitis — a painful, chronic respiratory condition prevalent in commercial layer flocks

Welfare Considerations

Respiratory disease in poultry is both a major welfare issue and a reliable indicator of suboptimal housing conditions. The scale of the problem — affecting hundreds of millions of birds in commercial flocks — reflects the conditions of intensive production that create ideal pathogen transmission environments. Subclinical infection is particularly insidious: birds that appear healthy are experiencing ongoing respiratory discomfort, reduced oxygen exchange during activity and chronic immune activation, all of which impair welfare and productivity simultaneously. The most welfare-effective responses are environmental — reducing stocking density, improving ventilation, managing litter moisture — combined with robust vaccination programmes for the most severe pathogens.

What You Can Do

Work with your vet on a flock-specific vaccination programme for IBV, Newcastle disease and Mycoplasma as appropriate
Audit ventilation systems regularly — target airflow rates that maintain ammonia below 20ppm at bird level
Implement all-in-all-out management to break pathogen transmission cycles between flocks
Use post-mortem and air sac lesion scoring at slaughter as welfare monitoring feedback on flock respiratory health
Train stockpersons to recognise early respiratory signs — rales, nasal discharge, reduced feed consumption — for prompt intervention
Maintain strict biosecurity — respiratory pathogens are frequently introduced by visitors, vehicles and new stock