Thymus Development in the Early Postnatal Period in Chicks When an Antibiotic and a Probiotic Are Introduced into the Diet

Abstract

Finding alternatives to antimicrobials in poultry farming is crucial to ensuring biosafety and food quality for humans. The purpose of this article was to provide a comprehensive description of thymus development in chicks of a hybrid egg-laying breed in the early postnatal period and to evaluate the effect of probiotics and antibiotics on this process. Materials and methods. The research focused on Hisex Brown cockerels (n = 100) from day 1 to day 20 of life fed on 4 different diets: standard diet (control), diet with a probiotic, diet with an antibiotic (enrofloxacin) and diet with their combination. Chicks’ thymus was studied using macroscopic morphometry and light microscopy. Results. The research demonstrated a significant increase in thymus weight in all the experimental groups compared to the control. In animals treated with a probiotic microorganism, by day 20 the histoarchitectonics in the thymus had become more complicated, with a clear delineation of the regions, formation of Hassal’s corpuscles, and developed vascularization of the medulla as well as a significant increase in the relative area of the medulla (up to 43.40 %). The group that was given enrofloxacin showed less pronounced changes: the relative area of the medulla on day 20 was 40.76 %, which was virtually the same as in the control group (40.73 %). In the group that received enrofloxacin and a probiotic, by day 20 the relative area of the medulla had increased statistically significantly and reached 46.5 %. The dynamics of the relative areas of the cortex and medulla in the thymus of Hisex Brown chicks demonstrates a strong influence of the diet on the development of this organ. In the control group, we observed a stable but low development of the medulla, with the predominance of the cortex, which may indicate insufficient stimulation of the immune function on a standard diet. The groups that received a probiotic microorganism demonstrated a significant increase in the relative area of the medulla and a decrease in the area of the cortex. This emphasizes the positive effect of the diets with probiotics on the development of the thymus, which may improve the functional activity of this organ and the body’s immune response.