2008 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to determine eggshell microstructural characteristics and associated physiological profiles in Mycoplasma gallisepticum-vaccinated egg-laying chickens. 1b.Approach (from AD-416) Chickens will be monitored to determine the effects of MG infections on various properties of the eggshell, including its microstructure. Light and scanning electron microscopes with digital imaging systems will be used to measure eggshell parameters such as total shell thickness, mammillary cone thickness, and columnar region thickness. Digital micrographs will be taken to assess shell structural features including radial shell sections, shell membranes, and mammillary cones. Serum lipoprotein chacteristics (VLDL diameter and cholesterol recovery in VLDL, LDL, and HDL fractions) of eggs will be determined. The effects of diet supplements on MG-inoculated birds and the effects of inoculation of various MG strain overlays will also be studied in several consecutive trials. 3.Progress Report Studies have been underway to examine the effects of S6, F, ts-11, and 6/85 strains of Mycoplasma gallisepticum (MG) on eggshell micro-structural characteristics and associated physiological profiles in commercial layers housed in biological isolation units or a caged layer facility. The data from two trials have been collected concerning the effects of various MG strains and dietary regimens on the physiology of hens housed in a caged layer facility. The eggshells from the second trial have been collected, but have not been analyzed for eggshell ultra-structure analysis until further funding becomes available. Also, other trials (as replicates of previous trials) have been completed concerning the effects of pre-lay ts-11 or 6/85-strain MG inoculations and subsequent F-strain Mycoplasma gallisepticum (FMG) inoculation overlays on commercial layers housed in biological isolation units. This project was monitored via office visits and telephone conversations.