DOES METHIONINE ENHANCE IMMUNITY IN MYCOPLASMA GALLISPETICUM F STRAIN VACCINATED BROILER BREEDER PULLETS?

Abstract

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 infection. A total of 276 six-week old breeder pullets, of the Ross 308 strain were randomly allocated into four treatments, each with three pen replicates of 23 birds/pen. Pullets were given water ad libitum and feed as per the Breeder Manual recommendation provided by the breeding company. The trial was designed in a completely randomized design. The treatments were: 1) Vaccinated with excess methionine (VEM), 2) Vaccinated with adequate methionine (VAM), 3) non-vaccinated with excess methionine (NVEM), 4) non-vaccinated with adequate methionine (NVAM). Birds were assigned to different treatments, including vaccination via drinking water with AviPro® MGF at 6 weeks of age, and provision of dietary methionine as 100% and 120% of Met requirements in the adequate and excess groups, respectively. Results observed in this experiment indicate a slow rate of growth and colonization of MGF vaccine strain at the level of trachea. A delayed increase in colony forming unit that extended up to 6 weeks post-vaccination offers limited competitive exclusion of the F-strain against other Mycoplasma gallisepticum infections for a considerable period. 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 in VAM group to 0.82 / ml of tracheal swab suspension in VEM group. These results highlight the ability of excess methionine in enhancing innate structural immune response. Measured sera titer using an Elisa kit showed that eight weeks post-vaccination were required by 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. The 20% excess methionine above the modern breeder requirements proved to have a key role in enhancing adaptive and acquired immunity.