Probiotics in mass insect rearing: A meta-analysis

Interest in insects as food and feed is rapidly growing. With this, however, comes a move towards mass rearing and industrial scale production. This upscaling and industrialisation of the rearing process is likely to result in increasingly higher densities of insects during rearing, which facilitates disease spread. The fact that these insects are likely to be genetically closely related further increases the risk of infectious disease outbreaks. In tackling this risk, it is important that we do not resort to the mass use of antibiotics that has been seen in the livestock industry. Instead, alternative rearing practices should be developed. The idea of supplementing insect feed with probiotics to improve insect health and prevent pathogen spread is receiving increasing attention. We carried out a meta-analysis to systematically analyse the data on probiotic supplementation of insects reared for food and feed available to date. We collected 68 effect sizes from 22 studies on body weight gain with probiotic supplementation compared to without and ten effect sizes from six studies of differences in microbiome diversity. We found that overall, probiotics tended to increase insect growth rate but did not significantly impact microbiome diversity. Our analysis also highlighted two key literature gaps. Data are only available on one of the four insect species registered as novel food in the EU, Tenebrio molitor. Furthermore, there are currently very limited data on the protection against pathogens by probiotic bacteria in insects reared for food and feed.