Temporal changes in serum concentrations of acute phase proteins in newborn dairy calves

Age-dependent changes in blood concentrations of four bovine acute phase proteins (APPs), serum amyloid A (SAA), lipopolysaccharide binding protein (LBP), haptoglobin (Hp) and alpha(1)-acid glycoprotein (AGP), were examined using two groups of newborn dairy calves. APP concentrations were monitored for either 3 weeks (Group A, n=13) or 2 months (Group B, n=13) after birth. Blood was collected at day 0-1 (Group A only), day 3 and then once or twice weekly until the end of the study. The possible transfer of colostral SAA as a source of SAA in the offspring was investigated by determining SAA isoforms in the serum of calves and in colostrum of their dams. Serum concentrations of all four APPs were high after birth, and concentrations showed a gradual decrease during the first 3 weeks of life. The lowest concentrations were at 21 days of age, after which concentrations stabilized. The calves synthesized adult SAA isotypes, and circulating SAA was not derived from colostrum. The results indicated that post-partum elevation of APPs is associated with the birth process and/or factors in colostrum and not necessarily with disease-related processes. This stresses the importance of considering a calf's age when interpreting APP concentrations in serum.