The effect of birth weight on passive immunity transfer in kangal breed lambs

This study evaluates the influence of birth weight on the passive transfer of immunity (PTI) in Kangal breed lambs, a robust and economically significant Turkish sheep breed. A cohort of 38 healthy neonatal lambs was assessed to elucidate the associations between birth weight and key indicators of PTI, including serum Optical Brix percentage, total protein (TP) concentration, and gamma-glutamyl transferase (GGT) enzyme activity. Blood samples were collected 48–72 hours postpartum and analyzed using cost-efficient and field-applicable methods such as refractometry, automated TP quantification, and enzymatic assays.The findings demonstrated that lambs with birth weights below 4.53 kg exhibited significantly reduced serum Brix percentages (P=0.003), TP concentrations (P=0.002), and GGT activity levels (P=0.028), indicative of compromised colostral immunoglobulin absorption. Receiver operating characteristic (ROC) analysis established 4.53 kg as the critical threshold for sufficient PTI, with optimized sensitivity and specificity values across all parameters. Birth weight exhibited a moderate to strong positive correlation with TP (R=0.351) and GGT levels (R=0.471), while Brix refractometry correlated robustly with TP (R=0.880), underscoring their diagnostic concordance. This study underscores the necessity of breed-specific PTI thresholds, particularly for breeds such as the Kangal, known for their higher mean birth weights. The findings highlight the utility of serum Brix refractometry, TP, and GGT measurements as reliable, pragmatic, and cost-effective alternatives to traditional laboratory methods for PTI assessment. Ensuring timely and adequate colostrum intake in lambs below the identified threshold (<4.53 kg) is imperative for mitigating immunological deficits and enhancing neonatal survival outcomes in Kangal sheep husbandry.