Effects of the In Ovo Vaccination of the ts-11 Strain of Mycoplasma gallisepticum in Layer Embryos and Posthatch Chicks †

SIMPLE SUMMARY: Mycoplasma gallisepticum (MG) is responsible for reductions in egg production and other economic losses in the poultry industry. In this study, the potential application of in ovo vaccination of the ts-11of MG vaccine (ts-11MGV) in layer embryos for the subsequent early protection as well as live performance of pullets were investigated. The use of various dosages of live attenuated ts-11MGV ranging from 3.63 × 10(1) to 3.63 × 10(4) cfu that were delivered in ovo at 18 days of incubation were evaluated. The results of current study revealed that the in ovo injection of various dosage of ts-11MGV had no negative impacts on any hatch variables. Additionally, the higher dosage of ts-11MGV (3.63 × 10(4)) resulted in a reduction in body weight gain in three-week-old pullets in comparison to all other treatments. Furthermore, MG DNA remained undetectable for hatchling and three-week-old pullets and no serological response was observed at 3 weeks posthatch. Total flock protection from field-strain MG infections is facilitated by the prior systemic establishment of vaccine strains in pullets. Therefore, it is concluded that the ts-11MGV may not be an appropriate candidate for in ovo injection due to the lack of its presence in hatchlings and posthatch chicks subsequent to its in ovo administration. ABSTRACT: The transmission of the ts-11 strain of Mycoplasma gallisepticum (MG) vaccine (ts-11MGV) between incubated eggs and between hatchlings that was administrated via in ovo injection, and its subsequent effects on their posthatch performance were evaluated. Marek’s disease diluent alone (sham-injected) or containing either 3.63 × 10(1), 10(2), 10(3), or 10(4) cfu of ts-11MGV was manually in ovo-injected into the amnion on 18 days of incubation. Egg residue analysis, percentage incubational egg weight loss, hatchability of viable injected eggs, and hatchling body weight (BW) were assessed. Selected hatchlings from each treatment replicate group were swabbed in the choanal cleft for MG DNA detection. Female chick live performance was also assessed through 21 days of posthatch age. Unexposed control sentinel chicks were allocated to each treatment replicate group to assess horizontal transmission. Birds were later swabbed and bled respectively, for detection of MG DNA and IgM production at 21 days posthatch. In all birds, no MG DNA was detected and SPA tests for IgM were negative. Among all variables, only 0 to 21 day BW gain was significantly affected by treatment and was lower in the 3.63 × 10(4) ts-11 MGV treatment in comparison to all the other treatments. Because ts-11MGV does not exhibit vertical or horizontal transmission capabilities under commercial conditions, it may not be a good candidate for in ovo injection.