Breeding strategies to improve the egg's natural defence

Abstract

The risk posed by food borne pathogens in eggs has taken on a high priority for government and consumer. In Europe there has been concern that plans to move from battery cages may increase the risk from eggs. For this reason there is some pressure to demonstrate progress in reducing risk from eggs. At the level of the egg the approach has been to improve resistance of the eggshell to breakage using selection for quasi-static compression or specific gravity. The review will consider phenotypic measurement and developments in genetics and genomics that can place new tools in the hands of poultry breeders, should they want to use them. New phenotypic measurements that better describe the physical and antibacterial properties of the egg and eggshell need to be developed which accurately measure the egg's natural defence characteristics to complement the developments in chicken genomics. Acoustic resonance analysis to measure the stiffness of the eggshell and ultra-structural measurements using electron microscopy in pedigree populations are methods which have been examined. Also organic matrix measurements, antimicrobial properties and bacterial penetration measurements that have only been of academic interest may be used in test populations. Genetics and genomics can be used with these phenotypic measurements to identify genetic markers that can be used in selection programmes, rather than the measurements themselves, using whole genome scans for quantitative trait loci and association analysis with candidate genes. The availability of the chicken genome sequence and EST resources has made carrying out these analyses easier in pedigree breeding flocks. The relative power of SNPs and haplotype as genetic markers for association tests. Pharmacogenomics 2: 11-24. BAIN, M.M. (1992) eggshell strength -a relationship between the mechanism of failure and the ultrastructural organization of the mammillary layer. Use of luminescent strains of Salmonella enteritidis to monitor contamination and survival in eggs. Journal of Food Protection S59: 915-921.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

“…Selection for egg quality is an important component of the breeding strategies of companies that market egg-laying type hens. Indeed, consumers demand high quality products with strong eggshell, while reducing cost, guaranteeing eggs devoided of microbial contaminants, and improving the acceptability of rearing systems [130,131]. Most selection strategies to improve egg quality has focused on the shell’s physical properties (and its ability to resist shocks), stability of egg weight, egg-white quality, and yolk percentage.…”

Small Egg Diameter as a Selection Criterion of Broilers

“…Thus, rounded eggs (with a high shape index) are generally more nutritious than elongated ones. A number of authors noted that the shape of the egg does not depend on the methods of managing the hens, nor on the microclimate conditions or on the feeding characteristics, but is associated with the bird genotype [11][12][13][14][15][16].…”

Recent Approaches in Poultry Breeding

“…The cuticle is recognised as a structure which prevents the entry of microbes to the egg and Dunn [7] identified that genetics was likely to be a major factor affecting the amount of cuticle in the eggs. Most importantly, clear evidence was found which suggests that selection of the hens laying eggs with the best cuticle coverage will have less bacterial penetration [8].…”