The effect of subclinical Mycobacterium paratuberculosis infection on days open in Michigan, USA, dairy cows.
A prospective cohort study design was used to evaluate the impact of subclinical Mycobacterium paratuberculosis infection on days open in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. Participating herds were tested and productivity and reproduction records were monitored for 18 months. All cows > or = 24 months old were tested for M. paratuberculosis infection using the ELISA and radiometric fecal-culture (RFC) techniques. Test-negative cows were re-tested at the conclusion of the monitoring period. Multivariable regression models were used. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8% (223/533 animals tested). Adjusting for diagnostic sensitivity and specificity, this resulted in a calculated sample true prevalence of 59.9%. ELISA-positive cows (on average) had a 28-day increase in days open when compared to ELISA-negative cows (p=0.02). The diagnostic method used to define a case altered the apparent association between paratuberculosis test status and days open. Fecal culture was a less-effective diagnostic tool for use in herds with a high prevalence of infected animals. The increase in days open in the ELISA-positive cows was an indication that perhaps reduced estrus expression or an increased post-partum anestrous period occurred in the subclinically infected ELISA-positive animals. This might have been due to a negative energy balance associated with M. paratuberculosis infection.
Population Medicine Center, Michigan State University, East Lansing, MI 48823, USA.
Y J
YJ
Johnson-Ifearulundu
J B
JB
Kaneene
D J
DJ
Sprecher
J C
JC
Gardiner
J W
JW
Lloyd
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000209:etiology; D015331:Cohort Studies; D003612:Dairying; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces / Q000382:microbiology; D005260:Female; D007247:Infertility, Female / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D008824:Michigan / Q000453:epidemiology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000302:isolation & purification; D010283:Paratuberculosis / Q000150:complications / Q000453:epidemiology*; D015995:Prevalence; D011446:Prospective Studies; D012098:Reproduction