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

Mastitis is a widely occurring and costly disease in the dairy industry. The 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 identified, 14 different bacterial species were found. Staphylococcus aureus and Streptococcus agalactiae were the most common isolates with 19 (27.94%) and 14 (20.59%), respectively. There were no significant differences between the width and length of the 4 teats in different CMT reactions. There was, however, significant correlation between CMT reaction and teat width (r = 0.14 to 0.20). In addition, there was significant correlation between SCC and teat injuries (r = 0.13). The difference between number of SCC in CMT positive and negative cows, as well as EC positive and negative cows, was significant. It is concluded that some anatomical characteristics of the teat can affect the udder's susceptibility to mastitis. Therefore, bull selection programs may be targeted to improve mastitis control in dairy cow farms.