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

Lead Research Organisation: University of Liverpool
Department Name: Infection & Microbiome


The demand for poultry eggs and meat is increasing globally. The poultry industry contributes £4.6 billion per year to the UK economy. The UK produces more than 10 billion table eggs a year, 65% of which comes from free-range farms. Currently, no data is available on the total number of eggs lost in the free-range farms. However, based on a study by Scottish Rural College (SRU), it is estimated that egg losses amount to approximately 6-25% per flock, which totals to no less than 30-130 million eggs a year.

To date, there have been no retrospective studies on health and production of free-range flocks in UK, or on the influence of various routine farm practices on birds' health and production. In fact, in recent years, a new strain of hybrid hens (eg. HyLine) has been introduced to egg farming. These hens stay on egg production for over 100 weeks of age, instead of the conventional 72-80 weeks, but the pre-lay vaccination programme remains the same. There has also been much variations in in-lay health management such as type, frequency and duration of deworming, mite control, antibiotics usages, and in-lay vaccination farm activities. A notable observation by field veterinarians is that at present, there is no information on coinfection or waning immunity of free-range egg laying flocks on the drops in egg production and quality. Coinfection by one or more of the following pathogens have been strongly implicated with egg losses; i) infectious bronchitis virus (IBV), ii) avian metapneumovirus (aMPV), iii) Mycoplasma gallisepticum (Mg), Mycoplasma synoviae (Ms) and iv) Ornithobacterium rhinotracheale (ORT), and v) infectious laryngotracheitis (ILT), but to date, there is little or no scientific evidence. This proposed study, for the first time in the UK, investigates two main variables; coinfection and immunity levels of flocks from 16 weeks to culling ages of the birds. Flock health and production will be assessed concurrently to appreciate statistical association between these variables.

Results from the proposed project will establish a link between egg production pattern, immune status of flocks, influence of farm practices, and the role of single or coinfections. Science-based evidence from this study will be used to demonstrate the following, i) the normal and abnormal egg production patterns in free-range flocks in UK, ii) the association between various routine farm practices such as parasite control, vaccinal immunity, antibiotics usages on egg production pattern, iii) a list of common causes of EPQ drops, d) ways to strengthen the pre-lay and in-lay vaccination in order to sustain higher and prolonged immunity in flocks. The research outputs of this project would benefit the UK and global farming industry.

Technical Summary

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.


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