Preventing drops in egg production in UK free-range flocks: understanding the interactions between farm practices flock coinfections and immunity

The demand for poultry meat and eggs in the UK continues to rise. Presently, the UK produces over 10 billion eggs. An estimated 6-25% of egg production is lost due to complex infectious diseases and farming management problems. Field experiences suggest that such production losses occur in the later ages of hens, particularly in flocks above 45 weeks old. Field veterinarians believe that the egg losses in commercial egg laying free-range flocks in the UK are linked to various farm practices, coinfections and waning flock immunity. One or more of the following pathogens - infectious bronchitis virus (IBV), avian metapneumovirus (aMPV), infectious laryngotracheitis virus (ILT), Mycoplasma gallisepticum (Mg), Mycoplasma synoviae (Ms) and Ornithobacterium rhinotracheale (ORT) causes egg losses. The efficacy of various farm practices including in-pullet and in-lay vaccination, use of parasiticides against worms and mites, antibiotics usages and other routine practices may have a role in egg losses. To date, there is no scientific evidence to validate the above claims. The proposed study, investigates farm practices, coinfection and flock immunity, and attempts to identify interactions between these factors. For this, the study is divided into two main blocks, i) analysis of flock health and production data from 2018-2022, ii) to undertake farm flock studies in 36 flocks from 36 different farms, to assess the presence of coinfection and flock immunity against the most common and important infectious causes of EPQ drops. This research will provide information over the lifespan of hens to identify farm practices that supports the health of free-range flocks for a normal egg production pattern. This includes the benefits of in-lay IBV vaccination, deworming or antibiotic practices. By end of this project, recommendations will be provided to adjust or to change current vaccination practices to prolong and strengthen the vaccinal immunity in egg laying flocks.