In ovo isoquinoline alkaloid injection alters gut microbiota and improves tight junction gene expression in broiler chickens.

In ovo feeding (IOF) is a modern technique that involves injecting beneficial substances into bird eggs prior to hatching, aiming to enhance poultry health and productivity. This study investigated the effects of in ovo injection of isoquinoline alkaloid (IQ) on hatchability, early growth performance, jejunal tight junction gene expression (OCLN, CLDN-1, and ZO2), and cecal microbiome composition in broiler chickens. A total of 460 Indian River hatching eggs were incubated and randomly assigned to either a control group (CON) or an IQ-injected group (INOVO) at a dose of 150 µg/egg. Post-hatch growth parameters, body temperature, jejunal tight junction gene expression, and cecal microbial profiles were studied. In ovo IQ injection did not significantly affect hatchability or alpha diversity indices; however, it led to a transient increase in body weight during the early post-hatch period (days .3-7 post-hatch). Beta diversity analysis showed significant differences in microbial community composition between the groups. Notably, the relative abundance of beneficial taxa, such as Lactobacillaceae and Lactobacillus, was significantly higher in the INOVO group. Furthermore, in ovo IQ injection significantly increased jejunal expression of OCLN and ZO2. These findings suggest that in ovo IQ administration may enhance early growth, promote beneficial microbial colonization, and strengthen intestinal barrier function without compromising hatchability, offering a natural approach to improve poultry performance.