IgY-based passive immunity therapy significantly reduced neonatal calf diarrhea and Cryptosporidium spp. infection dynamics under field conditions

Introduction Neonatal calf diarrhea (NCD) remains a major challenge in dairy production systems and has One Health relevance because of its impact on animal health, antimicrobial use, and the circulation of zoonotic enteropathogens. Cryptosporidium parvum and bovine group A rotavirus (RVA) are among the most prevalent pathogens affecting neonatal calves. This study evaluated the effects of oral passive immunization with IgY-DNT Plus (Bioinnovo Terneros 2.0), a polyvalent egg yolk immunoglobulin Y (IgY) formulation targeting major NCD pathogens, including the C. parvum antigens P23 and TRAP. Methods A prospective controlled field intervention trial with systematic alternating allocation included 50 newborn Holstein calves (25 treated and 25 controls) on a commercial dairy farm in Argentina. Treated calves received IgY-DNT Plus during the first 14 days of life, and all calves were followed for 30 days for diarrhea and RVA and C. parvum shedding. Results IgY-DNT Plus-treated calves showed delayed onset of diarrhea (10.46 vs 8.96 days; P = 0.0056), fewer days with diarrhea (7.88 vs 11.04; P = 0.0108), and lower cumulative fecal consistency scores (AUC, 21.85 vs 32.80; P < 0.0001). Treated calves also had fewer RVA antigen shedding-positive days by ELISA (3.96 vs 5.60; P = 0.0066), whereas time to first RVA detection, cumulative RVA antigen signal, and corresponding CCIF-based outcomes did not differ significantly between groups. For C. parvum , time to first qPCR detection was delayed in treated calves (median, 11 vs 9 days; HR = 0.41, 95% CI: 0.220.75; P = 0.0002), which also had fewer shedding-positive days (6.08 vs 8.56; P = 0.0126) and lower cumulative molecular shedding (AUC, 17.17 vs 30.04; P = 0.0004). Discussion Overall, IgY-DNT Plus supplementation was associated with reduced NCD clinical burden and modified C. parvum shedding dynamics under natural-exposure conditions, whereas effects on RVA were more limited. These findings support further evaluation in larger multicenter field studies.