Serum Amyloid A as an Inflammatory Biomarker in Captive Japanese Sika Deer (Cervus nippon): Reference Intervals and Correlations with Hematological and Serum Biochemical Parameters

Serum amyloid A (SAA) is a major acute phase protein that increases rapidly during inflammation, infection, and tissue injury, but data on SAA in Japanese sika deer (Cervus nippon) remain limited. SAA concentrations were measured in 128 serum samples from 84 captive Japanese sika deer (Mageshima sika deer, n = 26; Formosan sika deer, n = 44; mixed-subspecies individuals, n = 14) at Kagoshima City Hirakawa Zoological Park, Japan, using two latex agglutination turbidimetric immunoassays, VET-SAA, and LZ-SAA. Reference intervals were established, and Spearman rank correlations were evaluated between SAA and hematological and serum biochemical parameters. SAA concentrations were also compared between healthy (n = 30) and diseased (n = 95) groups, and receiver operating characteristic (ROC) analysis determined optimal cutoff values. Reference intervals for VET-SAA and LZ-SAA were 0.00–6.73 mg/L and 0.00–0.96 mg/L, respectively. Both assays correlated significantly with total protein, globulin, albumin, the albumin-to-globulin ratio, band and segmented neutrophils, lymphocytes, and eosinophils. SAA concentrations were also significantly higher in diseased than healthy deer (p < 0.001). The area under the ROC curve was 0.972 for VET-SAA and 0.959 for LZ-SAA. These findings suggest that SAA reflects inflammatory status in Japanese sika deer and may serve as a useful supplementary biomarker for inflammatory assessment in this species.