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ARS Home » Southeast Area » Mississippi State, Mississippi » Poultry Research » Research » Research Project #437256

Research Project: Alternative Mycoplasma gallisepticum (MG) Vaccination Regimens for Enhancement of Protection Against Field Strain MG Infections

Location: Poultry Research

Project Number: 6064-32000-013-002-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 31, 2019
End Date: Jul 30, 2024

Objective:
As a collaborator over the next five years, plans are to contribute to the projects initiated concerning the prevention and control of mycoplasmosis in commercial egg-laying hens. My contribution to this work will involve providing expertise and resources to projects involving the commercial application and effects of in ovo-administered live attenuated Mycoplasma gallisepticum vaccines on the immunity, physiology, and performance of egg-laying hens.

Approach:
Preliminary trials will be conducted to test for the relative sensitivities and resistances of layer embryos and subsequent chicks to an FMG or alternate LAV (i.e. 6/85MG, ts11MG, or MG bacterin) at various dosages, calculated from commercial mass vaccination dosages in proportion to embryonic body weight at the age of injection. The results will be used to judge the general plausibility of employing the particular LAV for in ovo injection, and will serve as guide for its continued use at the same or different dosages. In these trials, 60 layer hatching eggs will be subjected to one of five in ovo injection treatments at 18 days of incubation (non-injected, diluent-injected, and either a low, moderate, or high LAV dosage in commercial diluent). Twenty eggs in each treatment group will be randomly set on each of three incubator tray levels. Day 0-12 and day 12-18 percentage egg weight loss; embryonic mortality; hatchability of set and fertilized eggs; hatch rate; and hatchling total and yolk-free body weights and yolk weights will be determined. Choanal cleft, trachial, and intestinal swabs will be taken on a subsamples of embryos and chicks from each treatment group to test for the absence or presence of MG colonization. PCR tests from the swabs will confirm the strain of MG colonizing the swabbed area. To maximize the accuracy and precision of the in ovo injection of vaccine into the amnion of embryos in accordance with their age and sex, a liquid dye will also be injected in a separate group of eggs in one or more of these trials. This will be accomplished using an established embryo staging method (Embrex in ovo staging system). Every 6 hours, starting and ending on Days 17 and 20 of incubation, respectively, 4 eggs from each tray level will be in ovo injected with 50 µL of dyed commercial vaccine diluent (containing dye for the labeling of embryonic tissues) and embryo stage score, gonadal sex, and yolk and yolk-free embryo body weights will be recorded. In subsequent trials, an FMG or milder LAV (i.e. 6/85MG, ts11MG, or MG bacterin) will be used at doses and embryo ages based on the results of the preliminary trials. In each trial, 340 layer hatching eggs will be subjected to one of five in ovo injection treatments at 18 days of incubation (non-injected, diluent-injected, and either a low, moderate, or high LAV dosage in commercial diluent). Sixty eight layer hatching eggs in each treatment group will be randomly set on each of 10 incubator tray levels. Similar randomized complete block experimental designs will be employed in both the setter and hatcher units. Similar to the preliminary trials, day 0-12 and day 12-18 percentage egg weight loss; embryonic mortality; hatchability of set and fertilized eggs; hatch rate; and hatchling total and yolk-free body weights and yolk weights will be determined. Choanal cleft, trachial, and intestinal swabs will likewise be taken on a subsample of embryos and chicks from each treatment group to test for the absence or presence of MG colonization. PCR tests from the swabs will confirm the strain of MG colonization and the strain of MG colonizing the the swabbed area.