The effect of Mycobacterium avium ssp. paratuberculosis (MAP) on dairy reproduction and culling is not as well-documented as some of the other costs attributed to this infection. Research published in the August Journal of Dairy Science offers some insight into this influence.

To better understand the implications of MAP infections and Johne’s disease in a dairy herd, the rates of calving and culling were calculated for cows in each stage of MAP infection relative to uninfected cows. Data from six commercial dairy herds, consisting of 2,818 cows with 2,754 calvings and 1,483 cullings, were used for analysis.

Every cow in each study herd was tested regularly for MAP, and herds were followed for between four and seven years. 

Not surprisingly, non-shedding animals were significantly less likely to be culled compared to animals in the low-shedding or ELISA-positive categories.

The researchers also observed an increased calving interval in animals shedding high levels of MAP compared to low-positive animals.