Intramammary infections change the composition of milk and increase electrical conductivity of milk and decrease milk electrical resistance. Electrical conductivity has been used to detect mastitis during last four decades. The aim of this research was to examine the reliability of the milk electrical conductivity measuring in detection of subclinical mastitis. The experiment was conducted on a dairy farm of Holstein-Friesian breed. A total of 113 quarter milk samples were examined, 55 samples from cows in first stage of lactation and 58 from cows in third stage of lactation. Electrical conductivity (EC) of milk samples was detected by Hand-held EC meter (Draminski mastitis detector). Quarter milk samples for bacteriological analysis were taken aseptically during the morning milking in sterile test tubes. Bacteria growth was not detected in 60 quarter milk samples (53.1%), while in the other 53 samples bacteria was found (46.9%). The most common isolated bacteria in first and third stage of lactation was Corynebacterium spp. (38.9%) and coagulase - negative staphylococci (3.54%). High quality and healthy milk with Draminski mastitis detector was observed in 59.29% of the samples (67/113). Cows with mastitis may not always show an increased EC of milk from the infected quarter. Electrical conductivity of milk can give useful informations about udder health status, but hand-held EC meters, such as Draminski mastitis detector, cannot be used alone in diagnosis of subclinical mastitis. [Projekat Ministarstva nauke Republike Srbije, br. TR 31034]

One of the most important problems in milk production, causing great economic loses is certainly mastitis. In order to minimize economic losses from mastitis dairy farms introduce different mastitis management programs. These programs include mastitis therapy and prevention. In mastitis control prevention is most important and when mastitis occurs cost of therapy and milk discharge is very important. In our study we examined cost of mastitis treatment and milk loss in different mastitis management programs. We concluded that most costly are mastitis caused by specific pathogens. Cost of milk loss is 2.4 times bigger than cost of drug consumption. Applying of tit-dipping has great importance in reduction of mastitis caused by specific pathogens and less importance for conditional saprophytes. In total, cost of mastitis treatment on whole farm was almost the same for all mastitis management programs, while the effect of the program on farm C was the most expensive in the cows with the finding of specific pathogens.

Background: Lactoferrin and immunoglobulin G in milk have an important role in udder resistance to infection in the involution period. Both proteins express antimicrobial activity- lactoferrin by the binding and sequestration of iron ion; and immunoglobulin G by complement activation, bacterial opsonization and agglutination. Many factors affect lactoferrin and immunoglobulin G concentrations in bovine milk, such as the stage of lactation, milk production, and intramammary infections. The aim of this study was to determine concentrations of lactoferrin and immunoglobulin G in milk from healthy cows and subclinical mastitic cows during the late lactation period, and to evaluate the relationship between them.Materials, Methods & Results: A total of 150 quarter milk samples from 41 cows (Holstein-Friesian breed) in late lactation period were reviewed in this study. Milk samples were collected during morning milking, using aseptic techniques in sterile test tubes. From each sample, 0.1 mL of milk was plated on Columbia blood agar base with 5% defibrinated ovine blood, MacConkey agar and Sabouraud dextrose agar and incubated for 24 h - 48 h (bacteria) and 5 days (yeasts, mould) at 37oC. Milk samples for detection lactoferrin and immunoglobulin G concentration were skimmed at 1,400 g for 45 min and stored at -20°C until analysis. Lactoferrin concentration in bovine milk was determined using the Bovine Lactoferrin ELISA Quantitation Set. Milk samples were diluted at a ratio of 1:10,000. Plates were read at 450 nm absorbence values. Immunoglobulin G concentration was determined by the immunodiffusion method using radial immunodiffusion (RID) plates. Milk samples were diluted in a ratio of 1:30. Reading of results was done after incubation for 48 h by measuring the diameter of the precipitation ring. The highest mean lactoferrin concentration was observed in udder quarters infected with contagious pathogens (Streptococcus agalactiae and Staphylococcus aureus), while the highest mean immunoglobulin G concentration was detected in milk samples where minor mastitis pathogens (coagulase-negative staphylococci and Corynebacterium spp.) were isolated. Milk samples where Staphylococcus aureus was isolated had the lowest immunoglobulin G concentration, and the lowest lactoferrin concentration was observed in samples infected with enviromental pathogens (Streptococcus dysgalactiae).Discussion: This study showed that lactoferrin and immunoglobulin G concentrations are higher in milk samples from subclinical mastitic cows than in milk from normal lactating cows. Lactoferrin concentrations in milk samples from udder quarters infected with major mastitis pathogens were significantly higher than in milk infected with minor mastitis pathogens. The lowest concentration of immunoglobulin G was detected in milk samples where Staphylococcus aureus was isolated, while the highest immunoglobulin G concentration was observed in milk samples from quarters infected with minor mastitis pathogens. Lactoferrin and immunoglobulin G concentrations were significantly and positively correlated in all milk samples. This means that cows with high lactoferrin concentrations have high immunoglobulin G concentrations. In quarter milk samples infected with Staphylococcus aureus, lactoferrin and immunoglobulin G concentrations were negatively correlated. The cause of these findings could be the suppression of local immune response of mammary gland.

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The objective of the work was to examine the intensity of the local immune response of the mammary gland and the changes in the differential blood count of chronically infected cows. An experiment was performed on a group of cows with Q fever serologically proven using the ELISA test (IDEXX). Based on the ELISA test results, an experimental group of ten infected cows was formed. Blood was sampled from the experimental cows, and cumulative milk samples were taken. The number of erythrocytes was determined spectrophotometrically, and the number of leucocytes using the method according to Bürker - Türk. The blood analysis established an increased number of erythrocytes, while the number of leucocytes was within the limits of physiological values. The milk samples were used for the determination of the number of somatic cells using flow cytometric measurements. The processing of the milk samples established an average number of somatic cells of 853.000 /mL milk