In-Ovo Injection of Oregano Oil after Day 12 of Embryonic Development Did Not Affect Hatchability in Broiler Chickens

The use of antimicrobials in agriculture including broiler production is cause for concern due to the development of antibiotic resistant pathogens affecting both farm animals and humans (Marshall and Levy, 2011). Essential oils (EO) have been considered as promising alternatives to antibiotics. The aim of this study was to establish a standard in-ovo intervention using oregano EO to enhance resilience of new-born chicks against pathogens without compromising post-hatching performance. One important factor in developing a standard in-ovo method for EO is related to the stage of embryonic development. Embryonic development at early stages occurs much more quickly and the pH buffer system is not well developed compared to later stages. Therefore, we hypothesised that in-ovo injection of oregano EO during early embryonic development (before day 12) will reduce hatchability compared to a late intervention.

In this study, 0.1ml of oregano oil with concentration of 0.5% was injected into fertile eggs at different days (treatments) of incubation (day 0, 4, 8, 12, 16, and 17.5) at a rate of 100 eggs/treatment (n=100). Injection was performed under the inner shell membrane using disposable needles (25G 5/8’’). A non-injected control group was also included (control). Hatchability and performance parameters for 7 days post-hatching were compared between different treatments using ANOVA in GLM procedure of SAS 9.4. Results showed that in-ovo injection of oregano oil at days 0 and 4 of incubation compared to non-injected group significantly reduced the hatchability, 62.2% and 43% compared to 87.9%, respectively (P< 0.05; Table 1). In addition, hatchability of the group injected at day 8 (79%) was significantly lower than the day 12 group (92%) (P< 0.05; Table 1). There was no significant impact of in-ovo injection of oregano at different days of incubation on the performance for 7 days post-hatching.

In conclusion, in-ovo injection of oregano oil in broilers should be performed when the embryo is at least 12 days old to avoid any compromise of hatchability and post-hatching performance. The detrimental effect of early injection (before day 12) of oregano EO, which has acidic pH of 4.6, could be due to low buffering capacity of the early-stage embryo and interruption of the high pace of embryonic development.

ACKNOWLEDGEMENTS: This study has been funded by AgriFutures Chicken Meat.