Increased milk concentration of nitric oxide and lysozyme is associated withlisterial mastitis of different animal species

The aim of this study was to evaluate nitric oxide (NOx) (sum of nitrite and nitrate as indicators of endogenous nitric oxide production) and the indigenous enzymatic lysozyme concentrations in milk of lactating she-camel, buffaloes, cows, goats and ewes as markers on both mastitis severity and the causing pathogen Listeria. The relationship between Listeria species and NOx concentrations, as well as correlation between NOx concentrations and lysozyme was also assessed. Composite milk samples of all lactating animals in the selected farms were primarily tested for mastitis severity levels including clinical and subclinical mastitis using the California Mastitis Test. All composite milk samples were collected for NOx and the immunoactive protein lysozyme measurement and bacteriological analyses. Results showed that NOx and lysozyme in clinical mastitis was highest in comparison to sub-clinical mastitis and healthy udders. Listeria had a significant increasing impact on the level of NOx in she-camel, buffalo, cow, goat and ewe milk. On the other hand, Listeriahad a significant increasing impact on the level of lysozyme in she-camel, cow and goat milk while in the buffalo and ewe milk the Listeria infection did not induce a significant influence on the level of lysozyme in the milk.A significant positive correlation was found between NOx and lysozyme levels in the she-camel (r = 0.76; P < 0.01), cow (r = 0.86; P < 0.01) and goat (r = 0.28; P < 0.01). In conclusion, differences in both severity of mastitis and mastitis pathogens were associated with differences of NOx and lysozyme products in infected udders.