Agriculture Reference
In-Depth Information
days 8 to 14 have ranged from 2.9×10
5
cells/ml (Hurley and Grieve, 1988), up to 8.5×10
6
cells/ml (Garst
et al.
, 1999), with others reporting 1 to 2×10
6
cells/ml (Evans
et al.
, 1982;
Schollenberger
et al.
, 1986a).
The differences in reported SSC in sow colostrum and milk may arise from several
sources. Subclinical mastitis in dairy cattle is often determined by observing an
associated increase in SSC in the absence of clinical symptoms. An elevated SSC would
be expected in the case of either clinical or subclinical mastitis in the sow. The presence
of subclinical mastitis often is not accounted for in studies evaluating SCC in swine. The
route of oxytocin administration for milk collection also affects SCC, with intramuscular
administration resulting in higher SCC than intravenous administration (Garst
et al.
,
1999). Others have reported that hind milk, the milk removed by oxytocin administration
after piglets have suckled, is higher in total solid and milk fat (Atwood and Hartmann,
1992). A similar variation in SCC among fractions of milk removed has been reported in
cow milk (Paape and Tucker, 1966). Incomplete removal of milk from the sow's glands
may therefore result in underestimated estimates of SSC. In addition, different methods
have been used to determine SSC, including direct microscopic cell count (Evans
et al.
,
1982; Hurley and Grieve, 1988) or analysis of milk samples by a dairy herd improvement
laboratory primarily used for dairy cattle milk analyses (Garst
et al.
, 1999). Milk cells
often are collected by centrifugation of milk samples and evaluation of the resulting cell
pellet. However, cells are also found in the fat or cream fraction of milk that has been
centrifuged (Phipps and Newbould, 1966), and care should be taken to account for this
portion in estimates of SSC.
Milk cells include several leukocyte types, including neutrophils, macrophages,
lymphocytes, and eosinophils, as well as epithelial cells (Lee
et al.
, 1983; Le Jan, 1995;
Schollenberger
et al.
, 1986b,c). Table 9.8 summarizes the average differential cell
count of sow colostrum and milk based on studies that distinguished all five cell types.
Neutrophils are the major cell type at all stages of lactation. Highest concentrations of
Table 9.8. Average and range of reported differential cell counts in sow colostrum and milk.
1
Colostrum
2
Milk (days 3-7)
Milk (days 14-21)
Cell type
%
Range
%
Range
%
Range
Neutrophils
64.9
61.2-71.1
47.9
40.7-55.4
41.1
28.2-51.3
Macrophages
9.5
1.3-24.5
12.0
8.6-15.5
11.0
5.5-16.3
Lymphocytes
18.1
8.8-26.5
15.3
7.9-22.8
9.8
6.0-12.2
Eosinophils
0.7
0.2-1.5
1.5
0.4-2.6
0.8
0.2-1.5
Epithelial
6.0
0.4-19.6
23.2
6.1-36.8
37.3
31.3-48.0
1
References used for determining average differential cell count: Evans
et al.,
1982; Lee
et al.,
1983; Schollenberger
et al.,
1986a; Wuryastuti
et
al.,
1993.
2
Within 2 d of parturition.
