Abstract— Gastrointestinal infections are among the most significant health and economic challenges in animal husbandry, particularly in neonatal calves and small-breed dogs. Conventional antibiotic therapies are becoming increasingly limited due to microbial resistance, prompting the need for alternative biological solutions. Immunoglobulin Y (IgY), derived from egg yolk, represents an innovative, safe, and cost-effective approach for passive immunotherapy. This study aimed to evaluate the efficacy of orally administered IgY against bacterial and viral pathogens causing calf diarrhea and to preliminarily assess its potential in small-breed dogs affected by enteric infections. IgY was produced by immunizing laying hens with antigens derived from E. coli (K99), Salmonella spp., rotavirus, and coronavirus (based on Kolibin RC Neo). The antibody was extracted, purified, and lyophilized. Feeding trials in calves demonstrated reduced diarrhea duration and improved weight gain, while oral IgY supplementation in small dogs showed observable improvement in fecal consistency and appetite. The findings highlight IgY as a promising biotechnological tool for disease control and as a sustainable innovation in animal health management.

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