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 drastic
loss in the dairy industry. Oxidative stress, induced by reactive oxygen species (ROS), is believed to be a
primary factor in various cattle diseases including mastitis, but there are few studies regarding the role of
ROS in subclinical mastitis. This study was undertaken to i) study the changes in activities of erythrocyte
glutathione 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 with
subclinical mastitis and normal cows. Milk and heparinized blood samples were collected from 45 normal
cows 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 significant
difference (P>0.05) was shown between GSH-Px and SOD activities and also between the concentrations of
Cu and Zn in the studied groups. There was a marginal significant difference (P=0.05) between the Se
concentrations in the normal cows and cows with subclinical mastitis. The correlation between SCC and
SOD was positive and significant (P<0.05). It was concluded that optimum antioxidant intake in the feed
may enhance the resistance against subclinical mastitis.