Analysis of colostral proteins in calf serum by enzyme-linked immunosorbent assay

Enzyme-linked immunosorbent assay method was improved to monitor the concentrations of colostral proteins in the range of 10 to 10(3) ng/ml in calf serum. Colostral proteins were purified from fat-free colostrum, and antibodies against them were prepared from the rabbit anti-colostrum protein sera. Concentration of each protein was determined by enzyme-linked immunosorbent assay without interference by calf serum proteins in a mixture of colostrum and precolostral calf serum. Changes in the colostral protein concentrations in the sera of five postcolostral calves were monitored by enzyme-linked immunosorbent assay. After feeding colostrum to the neonatal calf, serum IgG concentration increased rapidly within 16 h to 8.1 to 36.8 mg/ml and gradually declined until 3 d to the steady levels, 4.7 to 23.6 mg/ml. The concentrations of casein and P2 (colostral small proteins, which were eluted at the second peak in Sephadex G-100 gel filtration) also increased more rapidly within 16 h to 9.6 to 264.0 micrograms/ml and 31.5 to 1600 micrograms/ml, respectively, and steeply decreased to near the detection limit on 3 d after feeding. These results indicate that enzyme-linked immunosorbent assay is useful to measure and monitor the absorbed colostral proteins and also to survey calves receiving and not receiving colostrum.