Does methionine enhance immunity in Mycoplasma gallispeticum F strain vaccinated broiler breeder pullets?

Summary This experiment was conducted to assess a protocol combining 20% excess dietary methionine above the modern breeder pullet's requirement and AviPro MGF vaccine in controlling Mycoplasma gallispeticum (MG) infection. In a complete randomized design, a total of 276 6-wk-old breeder pullets, of the Ross 308 strain were allocated into 4 treatments, each with 3 floor pen replicates of 23 birds/pen: 1) nonvaccinated with adequate methionine (NVAM), 2) nonvaccinated with 20% excess methionine (NVEM), 3) Vaccinated with adequate methionine (VAM), 4) Vaccinated with 20% excess methionine (VEM). Vaccination with AviPro MGF at 6 wk of age was performed via drinking water. Results indicated that the rate of depictable growth and tracheal colonization of MGF vaccine strain is 6 wk postvaccination. Sera Elisa titers showed that an 8-wk-postvaccination period was required for the vaccine to stimulate the humoral immunity response against MG. The 20% excess methionine numerically increased the IgG titer against MG in comparison to other groups, yet this increase was not enough to generate protective titer count. Furthermore, the addition of 20% excess methionine above the recommended levels hindered the tracheal colonization rate and log10 values of AviPro MGF vaccine colony forming units from 5.9/mL of tracheal swab suspension in VAM group to 0.82/mL of tracheal swab suspension in VEM group (P ˂ 0.05). In conclusion, the 20% excess methionine above the modern requirements reduced the tracheal colonization of F-strain MG. Further research is needed to confirm the ability of excess dietary methionine to enhance the adaptive and acquired immunity of broiler breeder pullets.