FIG. 2.

Infertility and cohort challenge are associated with an increased antibody trend for IgM. Median and quartile antibody trends for IgM for all uterine C. abortus inoculum doses are shown. (A) The antibody trend values for IgM of infertile heifers (nonpregnant; n = 12) are consistently higher than those seen with fertile heifers (pregnant; n = 18). (B) IgM trend values for cohort-challenged heifers (n = 10) are higher than those of herd mates that were not cohort challenged (n = 20). Cohort challenge indicates the exposure of inseminated heifers to C. abortus infection by shedding from heifers that had received uterine C. abortus inocula 2 weeks earlier. Animals that were inseminated during the first round of estrus were scored as not cohort challenged by herd mates that received uterine C. abortus inocula during the same time span. Animals inseminated 2 weeks later (during the second round of induced estrus) were scored as having been cohort challenged by their herd mates that were inoculated in the first round. Increased antibody trends for IgM were significantly associated with infertility (P = 0.001) and cohort challenge (P = 0.04) with C. abortus (Student's t test; mean of the results obtained with all intrauterine challenge groups).