Effects of the in ovo injection of an Escherichia coli vaccine on the hatchability and subsequent early post hatch characteristics of commercial layer chicks

Authors: Collins Elliott, Katie; LINDSEY, L - Mississippi State University; Evans, Jeffrey; Leigh, Spencer; Robinson, Kelsy; FATEMI, S - Mississippi State University; MOUSSTAAID, A - Mississippi State University; GERARD, P - Clemson University; Purswell, Joseph; PEEBLES, E - Mississippi State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2024
Publication Date: 12/4/2024
Citation: Collins Elliott, K.E., Lindsey, L.L., Evans, J.D., Leigh, S.A., Robinson, K., Fatemi, S.A., Mousstaaid, A., Gerard, P.D., Purswell, J.L., Peebles, E.D. 2024. Effects of the in ovo injection of an Escherichia coli vaccine on the hatchability and subsequent early post hatch characteristics of commercial layer chicks. Poultry Science. 104:104562. https://doi.org/10.1016/j.psj.2024.104562.
DOI: https://doi.org/10.1016/j.psj.2024.104562

Interpretive Summary: E. coli, or Escherichia coli, is a beneficial bacterium that commonly resides in the intestines of animals. Some strains of E. coli, however, have gained the ability to cause disease in birds/poultry and are called APEC (Avian Pathogenic E. coli). One vaccine that is given to poultry to provide protection against APEC is the Poulvac E.coli vaccine produced by Zoetis. This vaccine is normally given to chicks after they have hatched by spraying the vaccine on the chicks with water. The current research project investigated giving the chicks the vaccine earlier before they hatch through a technique called in ovo vaccination. In ovo vaccination typically delivers the vaccine to the amnion of the embryonic chicken. Since the embryo is smaller and potentially more sensitive, the typical dose of the vaccine was reduced or diluted. These dilutions of the vaccine were tested in this trial. The dilutions tested included the full dose of the vaccine at 107 colony forming units (CFU) of bacteria per egg, 105, 103, and 101CFU/egg. Control treatments for comparison included eggs that were not injected or vaccinated and eggs that were injected with the same diluent that the vaccine was diluted in (called the diluent treatment). The hatch of the chicks was evaluated and a subset of chicks were raised to 21 days of age. The body weight (growth) of the birds was taken each week, the length of the birds was taken at 21 days, and any mortality was noted during the entire test period. All the tested dilutions of the vaccine reduced the hatch of chicks in comparison to the control treatments. The body weight of the chicks was lowered in the highest dose at each measured age. The length of the birds at 21 days was also shorter in the highest dose (also indicating reduced growth). No birds died in the treatments except in the highest dose with 5.41% mortality occurring through 21 days of age. In conclusion, the tested dosages negatively affected hatch and the highest (full) dose of the vaccine delivered in ovo negatively affected the growth of the chicken through 3 weeks of age. Further research is needed to determine if any alterations in the vaccine or the method of in ovo vaccination could alter the reduction in hatch seen in this trial.

Technical Abstract: In the commercial table egg industry, avian pathogenic E. coli (APEC) can lead to significant economic loss and bird mortality. The Poulvac E. coli vaccine (PECV) (Zoetis, Parsippany, NJ) may be applied to protect against APEC infections. The purpose of this experiment was to in ovo vaccinate commercial layers with various doses of the PECV to evaluate hatchability and post hatch development of the chicks through 21 d of age. Eggs were either non-injected or vaccinated at 18 d of incubation with a diluent-injected control or one of the PECV treatments which included a full dose (2.65 x 107 E. coli CFU/egg) or dilutions of the full dose to produce 2.65 x 105, 2.65 x 103, or 2.65 x 101 CFU/egg. Mean hatch of injected eggs was significantly (P < 0.0001) affected by treatment, with all the PECV treatments significantly decreasing hatch. Mean chick BW was determined on d of hatch and at 1, 2, and 3 wk post hatch, and mean chick length was determined at 3 wk post hatch. Chick BW was significantly (all P < 0.0001) different between treatments at 1, 2, and 3 wk of age, with the chicks that had received diluent alone having the highest BW, and the chicks that had received the full dose having the lowest BW. Chick length was significantly (P = 0.045) different between treatments, with the chicks in the full dose treatment having a shorter body length than the chicks in the 2 control groups. Cumulative mortality from 0 to 21 d of growout was 5.41% in the full dose treatment, whereas no mortalities were observed in the other treatment groups. While layer chicken embryos were able to survive to 3 wk post hatch after having received the PECV by in ovo injection, the full dose of the vaccine increased cumulative chick mortality and decreased chick BW through 3 wk post hatch.