Özet:

Abstract The purpose of this study is to investigate relationship between milk somatic cell count (SCC), total bacteria count (TBC), milk glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and serum paraoxonase (PON) levels, to identify the role of these parameters in subclinical mastitis at cows in the first 100 days of lactation. Animal material of this study consists of 100 Holstein dairy cows which were raised in a farm in Ankara province. Selected animals were hosted under same conditions and had suitable feeding regimen for appropriate period and were in the first 100 days of lactation. Cows which have less than 200x103 somatic cell counts in two different analysis which performed 7-10 days apart considered as healthy (n=50), and which had 200x103 somatic cell counts in two different counts performed 7-10 days apart considered as subclinical mastitis (n=50). Serum paraoxonase (PON) activity was lower in cows with subclinical mastitis than healthy ones (p<0.001), and GSH-Px activity was higher in cows with subclinical mastitis (p<0.001). It was concluded that the changes in milk SOD and GSH-Px levels are affected by the antioxidant system of the udder in subclinical mastitis, that formed oxidative stress and because of that serum PON and milk somatic cell and total bacteria have negative correlation. In conclusion, it was pointed out that serum PON activity can be used as a marker in the diagnosis of subclinical mastitis and evaluation of the antioxidant status of the udder. Also, it was stood out to importance of udder antioxidant mechanisms to understand pathogenesis of subclinical mastitis especially occurs in first 100 days of lactation.

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