‘In Ovo’ Injection of Oregano Essential Oil on Day 17.5 did not Affect Hatchability in Broiler Chickens

Enteric diseases can severely affect health and welfare in broilers but can be effectively treated by antibiotics. However, complying with current consumer trends requires the adoption of other strategies away from these chemicals. One of the alternatives is essential oils (EO’s); plant-derived compounds that are used in poultry nutrition due to their antimicrobial, antioxidant and immunemodulating effects (Brenes & Roura, 2010). Little is known about using EO’s during embryonic development, referred to as ‘in ovo’. The main objective of this experiment was to identify the best day and site for ‘in ovo’ injection of EOs using oregano oil (OEO) as a model. Thus, this experiment aimed at testing the hypothesis that injecting OEO on d12 of incubation or later, using the least disruptive site of injection (air cell), would result in higher hatchability and better post-hatch performance compared to injections into other sites and control groups.

The experiment consisted of a 2x3 factorial design. 0.1mL OEO (0.5%) was injected on two days (d12 and 17.5) in three sites (air cell, amnion, yolk) with 100 eggs/treatment (n=100). A non-injected control and two quality controls injected with 0.9% saline (d12 air cell; d17.5 amnion) (n=40) were used. Treatments were randomly allocated to six levels of two incubators (Brinsea Ova-Easy 580) in groups of 25 or 10 (OEO and controls) and incubated for 18 days. At d12 and 17.5 eggs were injected on the blunt (air cell; amnion) or pointy end (yolk) with a 25Gx5/8” needle for the air cell at d12 and d17.5 and yolk at d17.5 and a 23Gx1¼” needle for the amnion at d12 and d17.5 and yolk at d12. At d18 eggs were transported to two hatchers (Greatlander 6BH) each with six levels divided into three compartments and split into 5 groups of 20 and 2 groups of 20 per treatment (OEO and controls). Groups were randomly allocated to a compartment and incubated until hatch. After hatch, chicks were moved to six brooders (Cimuka) in four groups of 20 and two groups of 20 per treatment (OEO and controls). Hatchability and 7-day post-hatch performance parameters were compared between treatments using ANOVA and pairwise comparisons (RStudio).

OEO injection on d12 decreased hatchability (76.5%) compared to OEO injection on d17.5 (85.4%) as well as the non-injected (89.6%) and saline (d12) injected (89.7) controls; therefore OEO injection before d17.5 may affect embryonic development. It remains to be investigated if this is related to possible toxicity caused by OEO in early (d12) but not late (d17.5) embryonic stages. No main effects of OEO injection on day and site of injection were found for body weight at hatch or 7 days post-hatch, feed intake and FCR. Body weight at hatch was lower (P< 0.05) for chicks injected with OEO in the yolk at d12 (45.89g), than in the amnion at d17.5 (46.83g), indicating an interaction between day and site of injection. An important aspect uncovered by this trial was a potential cytotoxic effect of OEO early in embryonic development that requires more research.

In conclusion, injecting OEO at d17.5 showed promising results regarding hatchability. The reduced hatchability when injecting OEO on d12 was unexpected and warrants further investigation.

ACKNOWLEDGEMENTS: This work was supported by AgriFutures Chicken Meat Program.