Effect of colostrum intake on alpha-lactalbumin concentrations in serum of calves.

Seven Friesian calves were fed colostrum for four days beginning within 24 hours of birth, and milk thereafter. The concentration of alpha-lactalbumin in serum was measured by specific radioimmunoassay and compared to IgG assayed by electroimmunodiffusion. Serum concentrations of alpha-lactalbumin peaked at 387 +/- 85 ng ml-1 within eight hours of initial intake of colostrum, declining to 12 +/- 3 ng ml-1 by day 6. IgG rose steadily to 17 mg ml-1 by 48 hours of birth and remained relatively constant thereafter. The temporal pattern of alpha-lactalbumin in serum following colostrum intake confirms previous studies suggesting reduced absorption of colostral proteins between 24 and 36 hours. The presence of variable amounts of alpha-lactalbumin in serum even after 17 days, however, indicates limited transfer of milk-derived proteins across the gut at this time. The data further show that cessation of maximal gut transfer does not relate to molecular weight of transferred protein.