الكاتب: Multiple References

Physical characteristics of the bovine teat canal were examined for their influence on susceptibility to intramammary infection. All quarters of 18 cows were inoculated with 2 x 105 cfu Streptococcus agalactiae (Trial 1) and 20 cows with 105 cfu Str. uberis (Trial 2) Z-k mm into the teat canal every 3 d for 12 d. Incidence of quarter infection was similar for both pathogens, 30/72 (42%) in Trial 1 and 32/80 (40%) in Trial 2. Logistic regression analysis showed that probability of infection by Str. agalactiae increased significantly with an increase in quarter peak flow rate (P < 0-05) whereas probability of infection increased for Str. uberis with a decrease in teat canal length (P < 0-05). A significantly higher (P < 0001) incidence of infection by Str. uberis was observed in quarters that contained a low wet weight (< 1-8 mg) of removable keratin compared with those that contained > 1-8 mg keratin, but there was no correlation between weight of keratin and length of the teat canal. Infections by Str. uberis took significantly less (P < 0-05) time to show a rise in somatic cell count above 7- 5 x 105 cells/ml than Str. agalactiae. The results provide evidence that these pathogens use different mechanisms to pass through the teat canal.