The Etiology of Mastitis and its Impact on Lipid Peroxidation Product of Dairy Cows

Worldwide, intramammary infection mastitis is still one of the most important disease in the dairy sector. The disease is usually local but may become systemic, although rarely, in immunocompromised animals. The milk collected from cows with different type of inflammation, including mastitis, is characterized by an increased number of somatic cell count (SCC) and changes in milk composition which usually affects its processing properties [1]. It was proved that the antibacterial activity of polymorphonuclear cells generates reactive oxygen species (ROS). The accumulation of the ROS correlating with a chemical and physical changes in the milk and can lead to oxidative stress. Increase of oxidative stress in dairy cows because of high milk production can result in excess Received: November 07, 2019 Published: November 14, 2019


Introduction
Worldwide, intramammary infection -mastitis is still one of the most important disease in the dairy sector. The disease is usually local but may become systemic, although rarely, in immunocompromised animals. The milk collected from cows with different type of inflammation, including mastitis, is characterized by an increased number of somatic cell count (SCC) and changes in milk composition which usually affects its processing properties [1].
It was proved that the antibacterial activity of polymorphonuclear cells generates reactive oxygen species (ROS). The accumulation of the ROS correlating with a chemical and physical changes in the milk and can lead to oxidative stress. Increase of oxidative stress in dairy cows because of high milk production can result in excess accumulation of ROS, which can induce lipid peroxidation and reduction of antioxidative activity [2].
One of the most reliable of lipid peroxidation product and widely used indexes of oxidative stress is MDA. Malondialdehyde is produced during the peroxidation of polyunsaturated fatty acids by the action of reactive oxygen species as a result of the depletion of antioxidant systems [3]. Oxidative stress in veterinary medicine and particularly in ruminant health is a relatively young field of research. Therefore, the goal of this study was to detect the etiology and occurrence of mastitis in dairy herd and their impact on lipid peroxidation product, using Milk Malondialdehyde.  For MDA detection were normal and mastitic milk samples skimmed by centrifugation at 10,000 g for 20 min at 4°C. Defatted milk was used for MDA concetration by spectrophotometric techniques. Malondialdehyde concentration was determined by the thiobarbituric acid method, which was modified from method of Andrei et al. [5].

Statistical Analysis
Data for milk MDA levels in selected groups of dairy cows were expressed as mean (M) ± Standard Deviation (SD). Difference between groups were analysed by using Analysis of Variance

Results and Discussion
High-producing cows are highly susceptible to Intramammary In addition, the IMI was positively associated with blood and milk MDA levels as the main cause of lipid peroxidation which is used as an indicator of oxidative stress. Milk with higher SCC has shown to have more infiltrated polymorphonuclear cells, and this caused an increase of oxidative reactions and apoptosis. Lipid peroxidation is a well-established mechanism of oxidative damage caused by reactive oxygen species, and measurement of the MDA provides a convenient index of oxidative stress [3]. In our study the mean level of MDA was significantly higher (P < 0.05) from mastitis milk samples compared with normal milk (Graph 1). In addition, a recent study showed that MDA was a mediator of a decreased milk yield in cows with CM and high SCC [3]. Our results indicate that not only milk from cows with CM but also with SM had higher MDA concentrations as compared to normal milk. Comparison of pathogens causing mastitis in this study showed that MDA levels were different among pathogens causing SM, MDA from quarter milk samples infected with Str. uberis were statistically higher compared to other pathogens (Graph 2).

Graph 2:
Comparison of milk MDA (nM mL -1 ) levels from selected bacteria causing IMI.

Conclusion
The results of the current study showed that bacteria such as staphylococci and streptococci were the principal factor causing intramammary infection. It should to keep in mind that polyetiological origin of mastitis in dairy cows means that the effectiveness of generally applicable mastitis control program in the reduction of environmental mastitis bacteria, in combination with the main contagious pathogens of the mammary gland tends to be limited. It is therefore necessary to implement new knowledge for diagnosing mastitis in dairy herds. The measurement of milk MDA level as a significant factor in alterations of the oxidant and antioxidant balance resulting in potent oxidative stress, could be a potential biomarker for diagnosing of mastitis and monitoring health status of udder.