A long-term study on the health status and performance of sows on different feed allowances during late pregnancy. II. The total cell content and its percentage of polymorphonuclear leucocytes in pathogen-free colostrum and milk collected from clinically healthy sows.

The main objective of this study was to determine the total cell content, TCC, and the percentage of polymorphonuclear leucocytes, PMNLs, in colostrum and milk collected from sows during the first 22 days of lactation. The pH-values during the same sampling period were also determined. It should be emphasized that all the values obtained emanate from bacteriologically negative colostrum and milk. The potential influence of different levels of late gestation feeding regimes was also evaluated. The TCC-values obtained from milk samples during the first 3 weeks of lactation and exceeding the designated threshold of 10 x 10(6) cells/ml varied between 4% and 21%. Within the TCC-limitation of 10-19.99 x 10(6) cells/ml neither the preceding nor the succeeding cell counts exceeded the threshold in 26.8%. TCC-values above 19.99 x 10(6) cells/ml were preceded and succeeded by cell counts below the threshold in 58.8% and 58.8%, respectively. The TCC-levels below the threshold of 10 x 10(6) cells/ml, expressed as geometric least square means, increased significantly from day 1 to day 3 (1.23 x 10(6) cells/ml versus 1.86 x 10(6) cells/ml) and decreased thereafter gradually to day 22 (1.38 x 10(6) cells/ml). When all values were included, the TCC-values increased in a similar pattern from day 1 to day 3 (1.38 x 10(6) cells/ml versus 3.18 x 10(6) cells/ml). The value on day 22 of lactation was still on a significantly elevated level compared with that of day 1 (2.10 x 10(6) cells/ml versus 1.38 x 10(6) cells/ml). The 2 different feeding regimes were not found to influence the TCC-values during the first 22 days of lactation. In the whole material the PMNL-values, expressed as percentages of the TCC, declined from approximately 60% on day 1 of lactation to between 40% and 50% for the remaining sampling period. This decline was comparable with the one seen in the cell class below the threshold of 10 x 10(6) cells/ml. In the 2 cell classes above 9.99 x 10(6) cells/ml, 78.0% and 88.8% of PMNLs on day 1 declined to about 40% on day 22. This might indicate an inflammatory response on day 1 but without any detectable bacteriological growth. The increase in lactation number, if lactation 1 was compared with the following lactations, revealed a significant rise (p < 0.05) in TCC-level and percentage level of PMNLs. A stepwise and significant increase in pH-level occurred between days 1, 3 and 8 (6.18, 6.56, 7.03) followed by a significant decrease to day 22 (6.91) when pH-values from milk of all cell classes were included.