On-farm hatching is a relatively new method in the broiler industry, in which fertilized broiler eggs are transported to the farms at the stage of 17–19 days of incubation. Once hatched, the broiler chicks have direct access to feed and water. Previous studies have shown on-farm hatching to increase animal welfare and intestinal development. However, no studies have yet aimed to quantify and compare the antimicrobial use in on-farm hatched flocks with that of traditionally hatched flocks. In this study, information on antimicrobial use (AMU) was collected from 211 Belgian conventional broiler farms, including data from 2244 traditionally hatched flocks and 227 on-farm (NestBorn) hatched flocks. On-farm hatched flocks had significantly (p < 0.001) more antimicrobial-free flocks (n = 109, 48.01%) compared to traditional flocks (n = 271, 12.08%) and a 44% lower (p < 0.01) treatment incidence (TI) at flock level (TI 8.40 vs. TI 15.13). Overall, the farms using traditional hatching had 5.6 times (95% CI 3.6–8.7) higher odds to use antimicrobials than the farms using on-farm hatching. Treated on-farm hatched flocks received three times less lincomycin-spectinomycin (linco-spectin) and less (routine) treatments at the start of the production round. However, both traditional and on-farm flocks experienced outbreaks later in the production round. These results show that on-farm hatching can contribute to the reduction in antimicrobial use in conventional broiler production.

Downtime, also known as an animal avoidance period, refers to a 24–72 h period during which individuals who have had contact with one animal species avoid subsequent contact with other susceptible species. This scoping review critically evaluated the effectiveness of downtime as a biosecurity measure. Peer-reviewed studies were identified and analysed using three electronic databases (Pubmed, Web of Science and Scopus). Two experimental studies directly evaluated downtime, nine additional articles examined human nasal carriage of pathogens after exposure to infected animals and seven articles evaluated the effectiveness of hygiene-based biosecurity measures targeting indirect mechanical pathogen transmission via humans (n = 14 unique articles in total; topical overlap noted where studies contributed to multiple categories). No evidence indicated an added benefit of downtime over other, more evidence-based measures such as hand hygiene, changing of clothes and boots and showering. While certain studies were able to identify the nasal carriage of pathogens, only one study indicated possible consequent transmission to naïve animals. This limited and species-specific evidence base reveals a critical gap between policy recommendations and scientific support for downtime. Based on these results, no clear benefit or necessity of downtime over other measures have been identified, other than its ability to deter unnecessary visitors, but these do not outweigh the impracticalities associated with an ‘animal avoidance period’. Resources and policy efforts should therefore shift from enforcing downtime toward ensuring and verifying adherence to fundamental hygiene measures.