Objective—To determine effects on production and
risk of removal related to Mycobacterium avium subsp
paratuberculosis (MAP) infection at the individual animal
level in dairy cattle.
Animals—7,879 dairy cows from 38 herds in 16 states.
Procedure—A subset of dairy cattle operations that
participated in the National Animal Health Monitoring
System Dairy 2002 study was evaluated via a serum
ELISA for antibodies against MAP and categorized
according to ELISA score. Dairy Herd Improvement
Association records were obtained to collect current
and historical lactation data and removal (ie, culling)
information. Production variables were evaluated on
the basis of serum ELISA category.
Results—Cows with strong positive results had
mature equivalent (ME) 305-day milk production, ME
305-day maximum milk production, and total lifetime
milk production that were significantly lower than cows
in other categories. No differences were observed for
ME 305-day fat and protein percentages, age, lactation,
and lactation mean linear somatic cell count score
between cows with strong positive results and those
with negative results. After accounting for lactation
number and relative herd-level milk production, cows
with strong positive results were significantly more
likely to have been removed by 1 year after testing.
Conclusions and Clinical Relevance—Without management
changes designed to reduce the farm-level
prevalence of MAP infection, paratuberculosis will continue
to reduce farm income by decreasing milk production
and potentially increasing premature removal from
the herd. (J Am Vet Med Assoc 2005;227:1975–1981)