PSI-17 - Anti-endotoxin immunoglobulin Y (IgY) time course of oral passive transfer and impacts on growth performance in foals

Abstract: Foal diarrhea is the leading cause of morbidity in neonatal foals and is often caused by various environmental pathogens. The adaptive immune system of foals depends on postpartum immunoglobulin absorption from maternal colostrum. To date, there lacks an easy way to supplement the immune system before intestinal closure. Thus, an anti-endotoxin IgY supplement derived from hyperimmunized hens may provide pathogen-specific protection if successful in passive transfer. Therefore, the objective was to determine the effects of an oral anti-endotoxin IgY on growth, stress, and passive transfer in neonatal foals with the hypothesis that IgY would successfully cross the gut barrier, positively impact growth, and ameliorate stress. To test this, 11 Quarter Horse foals were randomly assigned based on foaling date to one of two treatment groups for a 28-d trial. Upon signs of impending parturition, mares were moved to box stalls (3.7 × 7.3 m) and parturition was attended. At birth, foals were assigned to either the control (CON; n = 5) or treatment group (TRT; n = 6). Foals assigned to TRT were supplemented with 40 g egg-derived anti-endotoxin IgY oral supplement (Camas, Inc.) dissolved in 50 mL ddH₂0 at 20 minutes after nursing and again at 12 h postpartum. The CON foals received isovolumetric ddH₂O. Beginning at h 24 and daily thereafter, TRT foals received 1 g egg-derived anti-endotoxin IgY diluted in 5 mL ddH₂O. Blood samples were collected from foals prior to nursing at h 0 and following the first oral treatment at h 2, 6,12, 24 and d 3, 7, 14, 21, 28. Harvested serum was analyzed for IgG, IgA, IgY, and cortisol by commercial ELISA. Data were analyzed using PROC MIXED in SAS v9.4 with repeated measures of time. Vital signs were similar for all foals regardless of treatment (P > 0.24) and all growth parameters increased over time (P < 0.01). There tended to be a treatment × time interaction for wither height (P = 0.10) where TRT wither height was higher at d 28 (P=0.07). There was a treatment × time interaction (P < 0.01) for serum IgY concentrations where CON foals had undetectable levels for the duration of the study and TRT foals peaked on d 7 with detectable levels remaining on d 28. Cortisol, however, was not influenced by treatment (P > 0.29), and IgG and IgA concentrations were only influenced by time (P < 0.01). In conclusion, despite having no effect on vital signs and stress, IgY is passively absorbed following oral administration to neonatal foals without negatively impacting the passive transfer of maternal IgG or IgA, lending to future work on pathogen-specific protection against foal diarrhea.