In ovo delivery of essential oils has the potential to affect glutamate transport and carbohydrase activity in the jejunum of broiler hatchlings

Essential oils (EOs) are secondary plant metabolites, some of which can stimulate feed intake, and digestion. The capacity of the small intestine to digest and absorb nutrients early in the life of the chick depends on an adequate embryonic development of the villi and crypts and overall, the integrity and functional properties of the epithelia, including the expression and abundance of digestive enzymes and nutrient sensors and transporters. Some key transporters include the sodium-glucose transporter 1 (SGLT1), the excitatory amino acid transporter 3 (EAAT3), the peptide transporter 1 (PEPT1), and the fatty acid binding protein 1 (FABP1). Moreover, amino peptidase-N (APN) regulates catabolic enzyme digesting peptides, which release amino acids, while sucrase-isomaltase (SI) regulates a glycoprotein that plays an important role in the final degradation of carbohydrates in chickens.

This study investigated the impact of in ovo injection of EOs on these nutrient transporters and digestive enzymes at hatch. We hypothesized that in ovo injection of EOs would improve the capacity of the small intestine to digest and absorb nutrients during the late stages of embryonic development in broiler chickens. The study included 28 treatments (saline and 27 different EOs) selected based on their activity reported in the literature (Brenes & Roura, 2010). The eggs (24/treatment) were incubated under standard conditions. On embryonic day 17.5, 1 mL EO solution (5 µL EO+5 µL polysorbate-80+990 µL saline) was injected into the amnion. At hatch, jejunum samples from six hatchlings per treatment were collected for testing the expression of digestive enzymes APN and SI, and nutrient transporters SGLT1, EAAT3, PEPT1, and FABP1. Total RNA was extracted using RNeasy Mini Kit, QIAGEN. RNA quantity and purity were determined using a NanoDrop ND-8000 (Thermo Fisher, USA). The isolated RNA of each sample was reverse transcribed with the QuantiTect Reverse Transcription Kit. Quantitative PCR was performed using a SYBR Green with ABI QuantStudio 6 real-time PCR. The General Linear Model procedure in SAS 9.4 was used to compare the EO treatments with the control saline-injected group. Tukey test was applied for the multiple comparison and P < 0.05 was set as the threshold for significant differences.

The results showed that in ovo injection of spearmint, patchouli, and turmeric EOs significantly (P < 0.05) reduced the expression of EAAT3 compared to saline. This may affect the efficient transport of glutamate (Glu), a major metabolic fuel in enterocytes essential to the integrity and function of the jejunum, particularly in young chicks (Mott et al., 2008). In addition, bergamot EO significantly (P < 0.05) increased the expression of SI potentially improving carbohydrate digestion. No significant effects on the digestive biomarkers of interest were observed with the in ovo applications of the other 23 EOs.

It was concluded that in ovo delivery of spearmint, patchouli, and turmeric EOs may reduce the capacity to absorb Glu through the EAAT3 and that bergamot EO may increase carbohydrate digestion in the jejunum of broiler hatchlings.

ACKNOWLEDGEMENTS: This study was partially supported by AgriFutures and Delacon.