This study aimed to determine the levels of milk cell total protein
(TP), reduced nicotinamide adenine dinucleotide phosphate (NADPH), total
glutathione (tGSH), activities of glucose-6-phos- phate dehydrogenase
(G6PD) and glutathione peroxidase (GPx) in subclinical mastitic cows.
Milk from each udder was collected and grouped by the California
Mastitis Test. Then, a somatic cell count (SCC) was performed, and the
groups were re-scored as control (5–87 × 103 cells), 1st group (154–381
× 103 cells), 2nd group (418–851 × 103 cells), 3rd group (914–1958 × 103
cells), and 4th group (2275–8528 × 103 cells). Milk cell TP, NADPH, tGSH
levels, G6PD, and GPx ac- tivities were assessed. Microbiological
diagnosis and aerobic mesophyle general organism (AMG, cfu/g) were also
conducted. In mastitic milk, TP, NADPH, and tGSH levels, and G6PD and
GPx activities were significantly reduced per cell (in samples of 106
cells). In addition, milk SCC was positively correlated with AMG
(r=0.561, p<0.001), NADPH (r=0.380, p<0.01), TP (r=0.347, p<0.01) and
G6PD (r=0.540, p<0.001). There was also positive correlation between
NADPH (r=0.428, p<0.01), TP (r=0.638, p<0.001) and AMG. NADPH was
positively correlated with TP (r=0.239, p<0.05), GPx (r=0.265, p<0.05)
and G6PD (r=0.248, p=0.056). Total protein was positively correlated
with tGSH (r=0.354, p<0.01) and G6PD (r=0.643, p<0.001). There was a
negative correlation between tGSH and GPx activity (r=-0.306, p<0.05).
The microbiological analysis showed the following ratio of pathogens: Coagulase-Negative
Staphylococci 66.6%, Streptococcus spp 9.5%, Bacillus spp 9.5%,
yeast 4.8%, and mixed infections 9.5%.
As a conclusion, when evaluating the enzyme and oxidative stress
parameters in milk, it is more suitable to assign values based on cell
count rather than ml of milk. The linear correlation between the SCC and
AMG, milk cell NADPH, TP and G6PD suggests that these parameters could
be used as markers of mastitis.