Integrated Immune and Protein Profiles Predict Growth in Preweaning Lambs Independent of Feeding Regimen and Maternal Oxytocin Administration

Early-life nutrition and maternal management are important determinants of neonatal physiological development in ruminants. This study evaluated the effects of alternative feeding strategies and maternal oxytocin administration on growth, hematological traits, and immune-related biomarkers in preweaning lambs. A total of 96 newborn lambs were followed for 60 days under four management regimens: natural suckling (NS), colostrum followed by milk replacer feeding (MC+MR), early separation after colostrum intake with exclusive milk replacer feeding (MR), and natural suckling with maternal oxytocin administration (NS+OT). Body weight, serum protein fractions, immunoglobulin G (IgG), and hematological parameters were measured longitudinally. Data were analyzed using linear mixed-effects models. Principal component analysis was used to summarize the biomarker dataset, and the first principal component (PC1) was subsequently evaluated as an integrated physiological predictor of body weight. Body weight and serum IgG changed significantly with age across all groups (P < 0.001), whereas no significant main effects of feeding regimen or oxytocin treatment were detected for the primary growth outcome. PC1, representing a coordinated immune-protein and inflammatory profile, was positively associated with body weight. These findings suggest that preweaning lamb growth is more strongly associated with intrinsic physiological status than with the specific management interventions examined under the conditions of this study.