P23-Specific IgY Significantly Reduces Diarrhea and Oocyst Shedding in Calves Experimentally Infected with .

Background/objectives: is a zoonotic enteroparasite causing severe diarrhea in newborn calves, leading to significant economic losses in dairy and beef farming. This study aimed to evaluate whether p23-specific IgY antibodies could control neonatal calf diarrhea caused by .

Methods: A recombinant immunogen comprising the p23 protein fused to the antigen-presenting cell homing (APCH) molecule was expressed using the baculovirus system. Hens were immunized with the APCH-p23 immunogen, and the resulting IgY was spray-dried for treatment use. Eight newborn calves were included in the study and received commercial colostrum within the first 12 h of life. Four calves were treated with 20 g of powdered egg containing IgY (p23-specific IgY titer of 256 in milk) twice daily for 7 days. The remaining four calves received regular non-supplemented milk. All calves were orally infected with 6 million oocysts and monitored for 21 days.

Results: Calves treated with p23-specific IgY exhibited significantly reduced diarrhea duration (3.5 vs. 7.5 days; = 0.0397) and oocyst shedding duration (6.50 vs. 12 days; = 0.0089). In addition, the total number of excreted oocysts, as measured by the change of the area under the curve (AUC), was significantly reduced in the treated group (14.25 vs. 33.45; = 0.0117). Although the onset of diarrhea was delayed (3.5 to 6.5 days post-infection; = 0.1840), and diarrhea severity was reduced (24.25 to 17 AUC; = 0.1236), both parameters were not statistically significant.

Conclusions: P23-specific IgY antibodies effectively reduced the -induced duration of diarrhea in experimentally infected calves. These findings highlight the potential of this passive treatment as a promising strategy for controlling neonatal calf diarrhea.