In-Ovo Injection of Oregano Essential Oil Did Not Affect Hatchability or Post-Hatching Performance in Broiler Chickens

Plant-derived essential oils (EOs) contain functional phytochemical components that are used as feed additives to improve gut health and reduce the need for antibiotics. The injection of EOs into fertile eggs has the potential to influence the developing embryo including the gastrointestinal tract. This in turn may mitigate intestinal susceptibility and regulate gut microbial composition, resulting in long-term benefits in the chicken's life. However, some gaps in the in-ovo injection methodology such as the viable volume range without affecting embryonic development warrant further investigation. This study aimed to establish a range of volume injected of a fixed amount of EO without a negative impact on hatchability, embryonic development, and post-hatch growth. We hypothesized that high injection volumes would be detrimental to embryonic development due to the tight space in the egg and/or the excessive hydration of the egg compartments such as the yolk impairing fat mobilization.

In this study, 300, 600, 900, 1200, or 1500 µL of saline solutions all containing 0.5µL of oregano essential oil (OEO) were injected into the amnion of fertile eggs at day 17.5 of incubation (n=96 eggs per treatment). Dilutions were made with sterile saline using polysorbate 80 as an emulsifier. Hatchability and performance metrics up to 7 days post-hatching were compared between treatments using analysis of variance in SAS 9.4's generalized linear model procedure. Table 1 shows the main results. In-ovo injection of a fixed amount of OEO at varying volumes had no significant influence on hatchability (P > 0.05). The largest volume injected, 1500 µL, significantly (P < 0.001) improved BW0 compared to the control. However, by the end of the first-week post-hatch, there was no significant impact of the treatments on performance (P > 0.05). It is tempting to speculate that the excess water available in-ovo following the injection of the largest volume improved the hydration of the hatching embryo. After-hatch access to water seems to allow the other treatments to swiftly catch up. In conclusion, in-ovo injection of OEO at different volumes did not affect hatchability or early post-hatching performance in broiler chickens.

Table 1 - Effects of in-ovo injection of oregano essential oil (OEO) on hatchability and post-hatching performance (n=96). A fixed amount of OEO (0.5µL) was injected into the amnion at different saline solution volumes (from 300 to 1500 µL) at day 17.5 of incubation.