Evaluating differential lipopolysaccharide-induced behavioral, immune and plasma metabolome responses of St. Croix and Suffolk sheep

This study investigates different physical responses of St. Croix (STC) and Suffolk (SUF) sheep in response to lipopolysaccharide (LPS) challenge. Through a multidisciplinary approach encompassing physiological, immunological, and metabolic analyses, we aim to explore the mechanisms underlying disease susceptibility and resilience in small ruminants. Sheep were intravenously administered LPS at a dose of 2.5 µg/kg; blood and body temperature data were collected hourly. Behavioral observations were recorded during sampling and videos within pens were obtained 30 min after blood collection. An increase of body temperature by 1 ºC was observed in all groups (P ≥ 0.05). Significant variances were observed in leukocyte and neutrophil counts, wherein STC sheep displayed elevated cell concentrations compared to SUF sheep from 6 h following LPS injection until the conclusion of the sampling period (P ≤ 0.05). Additionally, SUF sheep exhibited greater hemolysis to acute LPS injury, as evidenced by higher optical density at 540 nm (P = 0.02). Behavioral assessment revealed a more pronounced grimace response in SUF sheep following LPS exposure, with an average sheep grimace score (SGS) of 2.67 compared to 1.25 in STC sheep (P < 0.0001). Metabolomic analysis demonstrated significant alterations in serum metabolite profiles between the two breeds, with 28 metabolites showing differential abundance (FDR ≤ 0.05). These findings contribute to a better understanding of host immunity and offer insights for targeted interventions to enhance disease resistance in small ruminants.