Serum Amyloid A Concentrations in Young Japanese Black Cattle: Relationship with Colostrum Intake and Establishing Cut-Off Concentrations

This study aimed to investigate the variations in serum amyloid A (SAA) concentrations and influencing factors in young Japanese Black (JB) cattle. The cut-off values were 18.5 mg/L, 17.7 mg/L, 14.4 mg/L, and 8.1 mg/L at 30-59, 60-89, 90-119, and 120-300 days of age, respectively. Calves that ingested colostrum had significantly higher SAA concentrations than those that did not. The SAA concentrations at 1-7 days of age showed no correlation with γ-glutamyltransferase, total protein, or globulin levels. A slight increase in mammary-associated amyloid A concentrations-a colostrum-derived SAA-was observed before and after colostrum intake on 1 day of age; however, a significant overall increase in SAA concentrations was noted. The reference values for the SAA concentration in 1-month-old calves also showed a gradual decline. These findings suggest that the elevated SAA concentrations in 1-month-old JB calves, similar to Holstein calves, are not due to absorption from colostrum but SAA is instead biosynthesized by the calves as a biological defense mechanism. The clinical application of SAA concentrations in JB calves after one month of age may contribute to improving calf productivity.