Prevalence of Giardia and Cryptosporidium andersoni and their effects on performance in feedlot beef cattle

Sixty individually housed Charolais crossbred steers originating from one ranch source had a 12-d (days 0–12) adaptation period in their pens to adjust to their ration and surroundings, followed by two consecutive backgrounding periods (85.5% roughage, 12% concentrate rations) with durations of 84 d (days 13–97) and 63 d (days 98–153), respectively. Steers had a 21-d adaptation period (days 154–174), followed by a 77-d (days 175–257) finishing period (20% roughage, 75% concentrate ration). Fecal samples and animal weights were collected from each steer every 28 d initially, then every 21 d during a test duration of 257 d. Feed weigh-backs were performed weekly for each steer. Fecal samples were processed, and Giardia duodenalis cysts and Cryptosporidium andersoni oocysts were counted. ADG, DMI and FE were calculated for each of the periods (Backgrounding Period 1, Backgrounding Period 2, Finishing Period 3 and Overall). Overall prevalence of C. andersoni and G. duodenalis was 85 and 82%, respectively. The...