Bovine tuberculosis is endemic in wild white-tailed deer (Odocoileus virginianus) in northeast Michigan, and deer are considered an important wildlife reservoir for transmission of bTB in that area. Understanding potential modes of transmission for Mycobacterium bovis, the causative agent of bTB, is important for mitigating the risk of infection for cattle herds. Feed contaminated by infected deer is believed to be 1 mode of transmission for M bovis to cattle.1 Results of a previous study2 indicate that M bovis can survive for at least 16 weeks on common feedstuffs (eg, apples, corn, carrots, sugar beets, potatoes, and hay) available to deer in northeast Michigan. Ensiled corn, alfalfa, and grasses are frequently fed to cattle in northeast Michigan, including herds identified as infected with bTB. The fields from which those feedstuffs are harvested are commonly grazed by white-tailed deer. Thus, feedstuffs could be contaminated with viable M bovis at harvest prior to ensiling. Some bacterial pathogens of cattle can survive the ensiling process including enterococci, streptococci,3 and Listeria monocytogenes.4 The investigators of 2 studies5,6 used PCR assays to monitor the persistence of MAP DNA in feedstuffs that were experimentally inoculated with the bacterium before being ensiled, and in both studies, MAP DNA was detected after the ensiling process was completed. Culturing of MAP was either not attempted6 or not successful5; therefore, the potential for MAP to remain viable and perhaps infectious in ensiled feedstuffs is uncertain. The objective of the study reported here was to determine whether M bovis could survive the ensiling process of feedstuffs commonly used to feed cattle in northeast Michigan.
Supported by the Michigan Milk Producers Association and Michigan Alliance for Animal Agriculture.
Mycobacterium avium subsp paratuberculosis
Mixed mostly grass
Bunzl Koch Supplies, St Louis, Mo.
EasyLog, Lascar Electronics Inc, Erie, Pa.
MV 31, Minipack America, Orange, Calif.
Hardy Diagnostics, Santa Monica, Calif.
BACTEC, Becton Dickinson and Co, Franklin Lakes, NJ.
EconoSpin, Epoch Life Science, Missouri City, Tex.
TaqMan Universal PCR Master Mix, Applied Biosystems, Waltham, Mass.
7500 Real-Time PCR System, Applied Biosystems, Waltham, Mass.
Dairy One, Ithaca, NY.
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