No abstract

Lactoferrin and Ig are the major glycosylated proteins in whey preparations from colostrum, milk, nonlactating bovine mammary secretions, and milk collected after intramammary endotoxin challenge. Lactoferrin was isolated from these sources and from bovine mammary tissue (nonlactating) and bovine milk neutrophils. Molecular weight forms of isolated lactoferrins were separated by SDS-PAGE. Apparent molecular weight forms of lactoferrin (approximately 83 and 87 kDa) did not differ among lactoferrins isolated from mammary secretions or from mammary tissue, but lactoferrin isolated from milk neutrophils migrated as different molecular weight bands in the gels (approximately 87 and 91 kDa). Human milk lactoferrin also separated as two distinct bands in the gels. All forms of lactoferrin were glycosylated. Differences were distinct in the glycosylation pattern of lactoferrins from human milk, bovine nonlactating mammary secretion, and bovine milk neutrophils. Enzymatic deglycosylation of lactoferrins from those sources resulted in migration of each as a single band (approximately 77 kDa). Apparent molecular weight forms of lactoferrin observed by separation by SDS-PAGE are not the result of genetic variance or differential glycosylation at different stages of mammary gland function. Nevertheless, the forms of lactoferrin result from the presence of glycans on the protein.

Colostrum and milk collected from 11 sows throughout lactation were used to estimate total and differential cell counts and N-acetyl-beta-D-glucosaminidase activity (NAGase). The mean log10 cell counts did not change significantly through the four weeks of lactation, ranging between 250,000 and 750,000 cells/ml. Polymorphonuclear neutrophils (PMN) decreased from about 56% of total leukocytes at day 1 (colostrum) to 12-14% at day 14 and day 21. Macrophages were 35% at day 1 and were the predominant cell type throughout the remainder of lactation, peaking at 77-80% at day 14 and 21. The PMN were again increased on day 28 (44% PMN vs 52% macrophage). The mean lymphocyte proportions ranged between 7.0 and 11.3% during the first two weeks of lactation and were decreased to 4.6-5.6% in the second two weeks of lactation. The activity of NAGase declined 9.5 fold (p less than 0.0001) between day 1 and day 14 with the greatest decline between day 1 and day 3. The activity of NAGase remained constant through the last two weeks of lactation. NAGase activity was significantly correlated with log10 of cell counts in sow milk (r = 0.42).

No abstract