Evaluation of the Effects of Colostrum Substitutes on Passive Immune Protection and Adaptive Immune Development in Neonatal Lambs

This study investigated how different colostrum sources impacted passive immunity transfer and adaptive immune development in Polypay lambs. Newborn lambs were assigned to four groups: fresh ewe colostrum (FrC; n=10), frozen ewe colostrum (FZ; n=11), frozen cattle colostrum (CC; n=11), or artificial cattle colostrum (AC; n=11). Lambs received 65 ml/kg colostrum within 4 hours post-parturition and were raised on milk replacer, creep feed, and hay. IgG concentrations were measured at birth and then weekly until 28 days of age (d). Lambs were immunized with 1mL ovalbumin (2mg/ml in PBS) at 35 and 63 d. Ovalbumin-specific antibodies were quantified. While no significant interaction (P ≥ 0.18) was found for total or relative IgG between FrC and FZ, a tendency (P = 0.06) suggested FrC yielded higher relative IgG at later time points (7, 14, 21, and 28 d). CC resulted in significantly (P = 0.02) higher IgG concen-trations than AC at 24 hours, 7, 14, and 21 d. FrC and AC showed a faster (1 week post immunization) and more robust (> 175%; P ≤ 0.07) ovalbumin humoral response compared to CC lambs 2 to 8 weeks post immunization. No differences were observed in fecal microbiome. This highlights the importance of choosing appropriate colostrum sources for optimal immune devel-opment in lambs.