Total and differential cell counts and N-acetyl-beta-D-glucosaminidase activity in sow milk during lactation

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).