1a.Objectives (from AD-416)
To determine if vaccination with a Mycoplasma gallisepticum (MG) bacterin at 10 weeks of age in conjunction with live TS-11 MG at 18 weeks of age has the potential to alleviate or ameliorate the performance depression experienced by commercial layers after a challenge with high passage F-strain MG at 45 weeks of age. Also, to determine the specific internal organ and tissue colonization sites of the various strains of MG.
1b.Approach (from AD-416)
Ten layer chickens will be placed in each of 16 biological isolation units at 10 weeks of age. The 16 units will be divided in to the following 4 treatment groups: Control; Vaccinated with MG bacterin at 10 weeks of age; Vaccinated with MG bacterin at 10 weeks of age followed by live TS-11 MG at 18 weeks of age; Vaccinated with TS-11 MG at 10 weeks of age. Birds in all treatment groups will subsequently be challenged by eyedrop inoculation with a 24-hour culture of high passage F-strain MG at 45 weeks of age. Eggs will be collected daily from each isolation unit beginning at the onset of lay to determine weekly hen-day egg production and total egg production for the entire lay period. In addition to various blood parameters, various internal egg and eggshell quality parameters including egg weight, eggshell breaking strength, Haugh Unit scores, and incidences of eggshell pimpling/blood and meat spots will be monitored. At trial termination, birds will be selected from each treatment group for histopathological evaluation, digestive and reproductive organ characteristics evaluation, and to test for the systemic presence of MG. Furthermore, the specific internal organ and tissue colonization sites of the various strains of MG will be determined through molecular techniques.
The first trial has been completed and the second trial is underway. Progress is being monitored by weekly visits to the research facility, telephone calls and via e-mail correspondence.