Why BelSU Scientists Say Probiotics, Not Antibiotics, Hold the Key to Poultry Health

Scientists at the Institute of Pharmacy, Chemistry, and Biology at Belgorod National Research University (BelSU) have demonstrated for the first time that antimicrobials do nothing to stimulate the production of key immune cells in poultry.

Led by Associate Professor Ulyana Krut of BelSU’s Department of Biotechnology and Microbiology, the research team examined the thymus – the central organ responsible for adaptive immunity. In healthy chicks, the absolute weight of the thymus grows rapidly during the first 20 days of life, while its weight relative to the bird’s total body mass peaks between days 5 and 10 before falling steadily. The scientists set out to discover whether that natural trajectory could be altered with pharmacological agents.

After carrying out detailed histological and morphometric analyses, the team reached an unequivocal conclusion: no dosage of antibiotic can accelerate the ‘construction’ of the thymus’s structural elements.

“We see that the organ’s weight relative to total body weight decreases after the 10th day – this is a completely normal physiological pattern,” Ulyana Krut explained. “Not only do antibiotics fail to speed up this process, they also do not interfere with the internal logic of the thymus’s architecture. To genuinely strengthen the body’s immune response, probiotic components must be included in the poultry diet at an early age – either alone or in combination with antimicrobial agents.”

In a parallel investigation, the team studied a probiotic supplement based on the bacterium Bacillus subtilis. Well known in veterinary and animal science, this microorganism proved to be a safe and moderate stimulant, particularly effective during the critical postembryonic period. Krut emphasised that the probiotic is not intended to replace antibiotics in the treatment of acute bacterial infections. Its value, she said, lies in gently reinforcing a chicken’s immune potential without running the risks associated with antimicrobial resistance – the ability of microbes to resist drug effects. This global challenge, fuelled by the uncontrolled use of antibiotics in agriculture for growth promotion and weight gain, underlines the importance of the BelSU research.

While the vast majority of applied studies ask whether supplements can simply enlarge the thymus, Krut’s team posed a fundamentally different question: how does a supplement alter the internal logic of the organ’s function, and what do those changes reveal about the fundamental laws of immune system development?

The scientists now plan to broaden their investigations to cover the composition and functional potential of the intestinal microflora in chickens. Future work will explore links between diet, weight gain, flock survival, and the quality of end products – meat and eggs.

The study was conducted under state contract FZWG-2023-0007 Adaptive Responses of Microorganisms: Theoretical and Applied Aspects and has been published in the Journal of Medical and Biological Research. It forms part of BelSU’s strategic project within the Priority 2030 programme.