Study of the relationship between oxidative stress and subclinical mastitis in dairy cattle

Subclinical mastitis is considered as one of the most prevalent diseases in dairy cows, causing drasticloss in the dairy industry. Oxidative stress, induced by reactive oxygen species (ROS), is believed to be aprimary factor in various cattle diseases including mastitis, but there are few studies regarding the role ofROS in subclinical mastitis. This study was undertaken to i) study the changes in activities of erythrocyteglutathione peroxidase (e-GSH-Px) and its functional component, selenium (Se); ii) compare the activities of erythrocyte superoxide dismutase (e-SOD) and its functional components, Cu and Zn in cows withsubclinical mastitis and normal cows. Milk and heparinized blood samples were collected from 45 normalcows and 45 cows with subclinical mastitis from dairy cows in Tehran province, Iran. Somatic cell counts(SCC), activities of GSH-Px and SOD and concentrations of Cu, Zn and Se were measured. No significantdifference (P>0.05) was shown between GSH-Px and SOD activities and also between the concentrations ofCu and Zn in the studied groups. There was a marginal significant difference (P=0.05) between the Seconcentrations in the normal cows and cows with subclinical mastitis. The correlation between SCC andSOD was positive and significant (P