Two experiments were conducted on commercial layer hens to study the effects of dietary supplementation with two levels of 25-hydroxycholecalciferol (25(OH)D₃) and two levels of calcium pidolate (with or without 25(OH)D₃) on production performance and egg quality. Experiment 1 was conducted using 90 Hy-Line Brown layer hens from 19 to 80 weeks of age and commenced in November 2012. Birds were divided into three groups of 30 hens as follows: group A (control group) fed with normal commercial layer mash feed, and groups B and C (treated groups) fed with normal commercial layer mash feed plus 0.5 g of 25(OH)D3 [premix (68.9 μg 25(OH)D₃)] per kg of feed and 1 g of 25(OH)D₃ [premix (137.8 μg 25(OH)D₃)] per kg of feed, respectively. Experiment 2 was conducted using 147 Lohmann Brown layer hens from 21 to 80 weeks of age and commenced in March 2014.

This project sought to correlate external shell features with underlying shell structures and examine if these structures are indicative of increased incidence of eggshell penetration by Salmonella Typhimurium. Eggs are an important nutrient and protein source in most cultures around the world, and the importance of food safety in intensive food production industries is likely to increase. Microbial infection of eggs is the source of approximately 49% of Salmonella food poisoning cases in Australia each year. The most significant source of these infections in Australia is Salmonella Typhimurium. Eggshell translucency is a phenomenon observed when an egg is candled over a light source; the underlying cause and incidence of eggshell translucency form the basis of our investigations of shell structures. In order to image eggshell structure, both Computed Tomography and Scanning Electron Microscopy were used to examine different structural components of the shell.