Cute-Egg, improvement of eggshell cuticle quality to reduce vertical transmission of zoonotic and pathogenic organisms

The poultry industry relies on artificial incubation of eggs to prevent the transfer of micro-organisms from one generation to the next. Despite this the vertical transmission from broiler and layer breeders to production flocks has been identified by the European food safety agency as the most likely route of transfer of antibiotic resistant e-coli and salmonella. There is also the opportunity for transmission of micro-organisms to occur during the collection and transport of eggs. Irrespective of the route or site of transfer, the entry of micro-organisms harmful to the egg contents is undesirable for food safety, animal and human health. The cuticle is a protein layer which covers the surface of the egg and fills the gas exchange pores in the shell through which the embryo 'breathes'. The cuticle forms the first line of defence to the penetration of bacteria derived both from transmission in the cloaca (where the egg and faeces exit the chicken) and transmission from the environment e.g. contact with collecting belts or handling equipment. In preliminary studies we have been able for the first time to quantify the cuticle deposition on eggs using a relatively cumbersome two-stage process and estimate the importance of genetics for this trait (heritability, 0.27). This suggested that the trait has good potential for genetic selection to improve it. We also have evidence that the natural variation in cuticle deposition is responsible for differences in the ability of bacteria to penetrate the egg. This demonstrated that eggs with good cuticle deposition were never penetrated by E. coli whereas eggs with poor cuticle quality were frequently penetrated. This means that selection for better cuticle deposition will reduce micro-organism contamination of eggs. In this proposal we will address the physiochemical, physiological and genetic parameters that characterise the cuticle and use this information to develop a simple one step measurement tool for cuticle assessment using the natural fluorescence of the cuticle. Both the amount and the degree to which the proteins are modified by the addition of sugar residues (glycosylation) will be quantified. In the first instance this will be achieved using a matrix of wavelengths of light both shone on and emitted from the egg surface. This will allow the wavelengths to be selected which can best distinguish the cuticle from potential interfering substances such as feather debri or pigment. A simple to use measurement tool will be built using this information. The amount of modification of the cuticle proteins by sugar residues will be assessed by how they change the rate at which the emission of fluorescent light occurs. Both measurements will be used to estimate reliably the contribution of genetics to variation in cuticle coverage in meat and egg laying strains of poultry. We will also determine genetic correlations with important production parameters to ensure there are no major negative consequences that might occur when the cuticle is selected for. As well as the contribution of genetics to variation in the trait, we will measure the contribution of environmental influences such as stress, age and how the hormones involved in the expulsion of the egg control cuticle deposition. In the project we will also characterise how the cuticle and its degree of modification by sugars acts both as a physical and a chemical barrier to bacteria and extend our understanding of the genes involved with cuticle formation and their expression. Overall this will provide the information required to allow accurate genetic selection for improved cuticle coverage to reduce the risk of pathogens entering the egg. We will also gain fundamental knowledge about the biological mechanisms which give rise to the cuticle and its role as a physical and chemical barrier to microbial penetration.