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The Incidence and Significance of New Coliform Mastitis Infections During the Dry Period

Dairy Pipeline: October 2000

Gerald M. (Jerry) Jones
Extension Dairy Scientist, Milk Quality and Milking Management
Virginia Tech
(540) 2314764-

"The Incidence and Significance of New Coliform Mastitis Infections During the Dry Period" was recently published in the Journal of Dairy Science by scientists from the University of Bristol in England. Duplicate aseptic milk samples were collected at drying off, prior to and after calving from each quarter of 629 cows from 6 commercial dairy herds. All six herds had low bulk tank somatic cell counts with a 3-month geometric mean of 250,000. Although E. coli made up 80% of the infections (5.3% of quarters after calving), small numbers of Enterobacter (0.32), Klebsiella (0.28), Serratia (0.12), Proteus (0.52), Citrobacter (0.20), and Morganella (0.08) also were found. A rise in the incidence of mastitis infection occurred between drying off and calving, going from 2.7% of quarters to 7.8%. New E. coli infections were detected in 8.6% of quarters. Of the mastitis that developed during the first 100 days of lactation, most developed within 30 days in quarters that became infected during the dry period . All cows had been dry treated. More infections occurred during the summer months (1997 which was "comparatively wet"). "Significant numbers of intramammary enterobacterial infections are acquired during the dry period and quarters that acquire an infection are more likely to develop mastitis in the subsequent lactation." The authors also concluded that environmental management during the dry period may greatly impact the incidence of enterobacterial mastitis (again 80% was E. coli) in the subsequent lactation. Many herds have had problems with mastitis or high somatic cell counts this summer. These may have been caused by E. coli (a coliform). Environments with muddy lots, dirty and wet bedding, poor ventilation, or access to wet areas such as ponds, streams, or shade trees may have contributed to new mastitis infections. Inclusion of vitamin E and selenium in the ration starting at three weeks before calving, and injections with selenium or an E. coli vaccine could be beneficial by helping build immunity, but not until environment challenges have been corrected.

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