Bumped kinase inhibitor (BKI) treatments reduce fecal oocyst shedding in calves having an established Cryptosporidium parvum infection. A, Daily oocyst shedding was significantly reduced in BKI-1294– and BKI-1517–treated calves on days 3–10 after infection (P < .05), compared with values for control calves. Daily oocyst shedding was significantly reduced in BKI-1553–treated calves on days 3 and 8–10 after infection (P < .05). B, The total number of oocysts shed over the duration of the trial was significantly reduced in BKI-1294–treated calves and BKI-1517–treated calves but not BKI-1553–treated calves, compared with control calves (P < .05), with BKI-1294 having a greater effect than BKI-1517 (P < .005). Data are for 18 control calves and 6 calves per BKI. Oocyst counts (daily and total) were examined for significant differences by the 1-tailed Student t test. Abbreviation: SD, standard deviation.