Preliminary bacterial study on subclinical mastitis and teat condition in dairy herds around Shiraz

Abstract

Mastitis is a widely occurring and costly disease in the dairy industry. Th e aim of this study was to isolate bacterial causes of subclinical mastitis and investigate the relationship between subclinical mastitis and teat condition in dairy herds located around Shiraz, Fars province, Iran. From 7 commercial dairy herds around Shiraz 354 lactating cows were selected randomly. Subclinical mastitis was evaluated by the California Mastitis Test (CMT), electrical conductivity (EC), and somatic cell count (SCC). Teat condition was evaluated by measuring teat width and length. In the 68 samples of bacterial cultures identifi ed, 14 diff erent bacterial species were found. Staphylococcus aureus and Streptococcus agalactiae were the most common isolates with 19 (27.94%) and 14 (20.59%), respectively. Th ere were no signifi cant diff erences between the width and length of the 4 teats in diff erent CMT reactions. Th ere was, however, signifi cant correlation between CMT reaction and teat width (r = 0.14 to 0.20). In addition, there was signifi cant correlation between SCC and teat injuries (r = 0.13). Th e diff erence between number of SCC in CMT positive and negative cows, as well as EC positive and negative cows, was signifi cant. It is concluded that some anatomical characteristics of the teat can aff ect the udder's susceptibility to mastitis. Th erefore, bull selection programs may be targeted to improve mastitis control in dairy cow farms.