Background: Subclinical mastitis is an important cause of economic losses in dairy cows in Rio Grande do Sul state (southern
Brazil) because the deleterious effect on the health of the cow and on the quality of milk. The difficulty of early diagnosis of this
problem had led to the study of early indicators of inflammatory conditions, as acute phase proteins, mainly haptoglobin and
fibrinogen, in the case of bovines. The aim of this work was to study the relationship between plasma values of haptoglobin (Hp)
and fibrinogen in dairy cows with somatic cell counting (SCC) in milk for testing the hypothesis that Hp or fibrinogen would be
adequate early indicators of subclinical mastitis.
Materials, Methods & Results: Milk and blood samples were collected in cows of herds from Rio Grande do Sul. Three groups
of 50 cows each were separated according to milk SCC. Samples of group 1 (healthy mammary gland) had SCC below 600.000 cell/
mL, samples of group 2 (subclinical mastitis) had SCC above 600.000 cell/mL without any signal of clinical mastitis and group 3
(clinical mastitis) was compound by samples from cows showing evident clinical signs of mastitis. Additionally, total bacterial
count (TBC) and concentration of lactose, fat, protein and total solids were determined in milk using infrared spectrophotometer.
Blood samples were collected by venipunction of the coccigeal vein for analysis of fibrinogen and Hp. Fibrinogen was determined
by the heat precipitation method and Hp by a spectrophometric method. The results showed lower concentration of lactose, fat
and total solids and higher concentration of protein in milk samples of cows with mastitis. Fibrinogen and Hp values were higher
in the mastitis group, but no differences were observed between healthy and subclinical mastitis groups. Significant correlation
coefficients were observed between plasma fibrinogen and milk SCC (r = 0.27) and between plasma Hp and milk SCC (r = 0.357).
Discussion: The health condition of the mammary gland and therefore the somatic cell counting is determinant in the composition
of milk so that an inflammatory condition may lead to decreasing values of lactose and fat as well as increment in total protein.
Decrease in lactose and fat composition of milk have been reported in many works as a function of the deleterious effect of
inflammation on the mammary tissue. Increase in milk total protein must be a direct effect of the inflammatory process, represented
by somatic cells, bacteria and other substances leaking from the injured secretory tissue. The lack of difference of the plasma
concentrations of haptoglobin and fibrinogen between subclinical mastitis and healthy mammary gland hinders the possibility
of discriminating cows with the subclinical condition of the problem. Hp in plasma samples belonging to cows of low milk SCC
is probably augmented by other factors than an inflammatory condition. The present study did not prove a clear usefulness for
using plasma values of Hp for diagnosing subclinical mastitis in dairy cows. However, the significant correlation coefficient
obtained between plasma Hp and milk SCC are worth of exploring more aspects of the relationships among acute phase proteins,
clinical and subclinical mastitis condition and quality of milk.
