This study provides an exhaustive toxicological and biotechnological evaluation of "Bursanatal," a novel veterinary immunomodulator derived from the lymphoid tissue of the avian Bursa of Fabricius. The drug’s active complex consists of low-molecular-weight regulatory peptides (1–10 kDa) obtained through a specialized multi-stage extraction and ultrafiltration process. The experimental design included an assessment of acute and subchronic toxicity (30-day oral and intraperitoneal administration) using outbred white mice and Wistar rats to determine the safety margins and cumulative potential. Systematic monitoring of hematological and biochemical parameters, alongside histopathological examination of visceral organs, was conducted. Furthermore, in vitro cytotoxicity was evaluated across five immortalized cell lines to ensure cellular safety. The results demonstrate that "Bursanatal" lacks significant toxicity, with an LD50 exceeding 6000 mg/kg, classifying it as a Class IV "low-hazard" substance according to international standards. The drug exhibited no adverse effects on hepatorenal functions or hematopoietic stability; conversely, a moderate stimulatory effect on lymphocytic populations was observed, suggesting its potential for correcting immunosuppressive states in industrial poultry and livestock. The technological workflow ensures the removal of high-molecular-weight ballast proteins, thereby minimizing allergenic risks. These findings establish a robust safety profile for the integration of "Bursanatal" into clinical veterinary practice as an eco-friendly alternative to traditional antibiotics.
