Studies on passive immunity in the foal: III. The characterization and significance of neonatal proteinuria

Abstract

A marked but transient proteinuria was detected in all foals that received colostrum in the first 24 h. of life. Initially there were rising levels of urinary protein which reached a peak by 6 to 12 h., followed by sharply declining levels to 24 to 28 h. of life. Feeding high protein colostrum during and after the time of intestinal closure did not prolong the period of proteinuria. Analysis of the urinary protein by CAM electrophoresis showed that it was devoid of obvious serum components. It more closely resembled the protein composition of milk and colostrum, but contained no evidence of γ-globulin. On gel filtration it was found to consist almost exclusively of low molecular weight protein. It was concluded that the small molecular weight milk proteins were absorbed by the intestine along with the larger molecules, but were selectively excreted in the urine by virtue of their small size. The cessation of proteinuria was judged therefore to be a reflection of cessation of absorption of macromolecules by the foal's intestine.