A comparison of milk protein status of healthy and mastitic cows under denaturing conditions

Mastitis is one of the most important diseases of dairy cattle in the world. The identification and characterization of the constituent proteins in milk can be useful for studying the biochemistry and pathogenesis of mastitis. In this study, the electrophoretic patterns of milk from 10 healthy and 30 mastitic cows were studied. All of the latter milk samples were California Mastitis Test (CMT) positive, and these were cultured to isolate the infective agents. The electrophoretic patterns of these samples and those of healthy cows (negative CMT and cultures) were studied with the SDS-PAGE technique. The approximate molecular weight of protein bands were categorized by their different flow rates (Rf), and these ranged between 18.5 - 220 KDa in mastitis samples of milk. The electrophoretogram showed that higher molecular weight bands appeared in the milk of mastitic cows60-220KDa and many were in the range of 176-208 kDa.The major band for the healthy samples was 220 KDa. In this respect, the mastitis samples had a minimum of two bands and a maximum of five bands, while milks from healthy cows did not show any bands in this range. On the basis of the different result between the electrophoretic patterns of milk from healthy and mastitic cows, it can be concluded that SDS-PAGE is a suitable method for the diagnosis of cows withsub sub clincal mastitis.