Background and Aim: The use of antibiotics as growth promoters in the feed of poultry, has contributed to an increase in the antimicrobial resistance of foodborne pathogens worldwide. Hence, the development of new effective alternatives to antibiotics that do not hinder productivity is imperative. For this, the aim of the present study was to determine whether oregano essential oil (OEO) extracted from Lippia origanoides is a suitable alternative to growth-promoting antibiotics (GPAs) for improving the performance, egg quality, and intestinal morphometry of ISA Brown laying hens. Materials and Methods: A total of ninety-six 70-week-old ISA Brown laying hens were randomly assigned to four treatment groups with four replicates per treatment and six hens per replicate. The treatments consisted of four different diets that were formulated according to the nutritional requirements of the genetic line and the production phase with and without the addition of GPA and OEO: NC, which did not contain OEO or GPA; GPA, which included 50 ppm zinc bacitracin as a GPA; 80OEO, which included 80 ppm OEO and no GPA; and 150OEO, which included 150 ppm OEO and no GPA. Results: All of the OEO and GPA treatment groups had a better feed conversion ratio than the NC group. However, the addition of 150 ppm OEO to the diet improved the percentage egg production and egg mass, as well as the external and internal quality of the egg compared with the other treatments. In addition, both the 80OEO and 150OEO treatments improved the yolk color, shell thickness, and shell color, as well as parameters related to the intestinal morphometry compared with the NC group. Conclusion: The findings of this study indicate that 150 ppm OEO can be used as a substitute for GPA to improve the performance, egg quality, and parameters related to the intestinal morphometry of ISA Brown laying hens.

AbstractThe potential of probiotics to manipulate the intestinal microbial ecosystem toward commensal bacteria growth offers great hope for enhancing health and performance in poultry. This study aimed to evaluate the efficacy of five probiotic-based formulations in modulating cecal microbiota in broilers at 21 and 42 days of age. Probiotics investigated included a synbiotic (SYNBIO), a yeast-based probiotic (YEAST), and three single-strain formulations of spore-forming Bacillus amyloliquefaciens (SINGLE1), B. subtilis (SINGLE2) and B. licheniformis (SINGLE3). Metagenomics analyses showed that the cecal microbiota of SINGLE, YEAST, and MULTI supplemented birds had low diversity compared to the control diet without probiotics (CON) at 21d. At the same age, birds fed SYNBIO had a high population of Lactobacillus salivarus and Lachnospiraceae, which was reflected in a singular microbial community illustrated by beta-diversity analyses. By 42d, there were no differences in alpha or beta-diversity in the microbiota of probiotic-treated broilers compared to CON. Birds treated with SINGLE2 had a lower abundance of lactic acid bacteria, while a higher (p<0.05) population of unidentified Lachnospiraceae and Ruminococcaceae. Although the investigated probiotic formulations shared similar taxonomy, modulation of microbiota was not a core outcome for all probiotic-treated broilers indicating the success of microbiota-based intervention may ultimately be dependent on probiotic mixture and broiler’s age.