Abstract
New immunological bioactive parameters are needed for the early detection of subclinical mastitis in dairy animals beside somatic cell count (SCC). A total number of 80 quarter subclinical mastitic (SCM) milk samples and 10 quarter normal milk samples were collected from dairy cows for detection of causing bacteria, some immunological bioactive parameters as well as apoptosis that occur in milk somatic cells (SCs) as a result of SCM and bacterial infection. The main isolated bacteria were Staphylococci that were isolated from all SCM milk especially when SCC exceeded800x103 cells/ml. SCC were significantly correlated with the severity of SCM as well as the tested immunological parameters eg. haptoglobin (Hp), milk amyloid A (MAA), lactoferrin (Lf), Lysozyme, lactate dehydogenase enzyme (LDH), nitric oxide (NO) and heat shock proteins (HSPs 60) (p < 0.05). The highest significant correlation of these bioactive parameters was detected when SCC exceeded 800x103cells/ml. From the in vitro cultivation of SCs, it was found that they are one of the major sources of immunological parameters that can be used for detection of SCM especially in its early stages. Apoptosis that occurred in SCs was affected by their number as well as the type of bacteria that infected the mammary gland. Furthermore contagious bacteria represented by S.aureus in the in vitro apoptotic assay had the stronger effect on SCs DNA integrity and DNA-fragmentation than the environmental once represented by E.coli.

Key words: Cow’s milk; SCM; SCC; bioactive immunological parameters; SCs apoptosis; comet assay.