473 Evaluation of hematology outcomes as indicators of liver abscess formation in beef × dairy cross steers

Abstract Our objective was to evaluate hematological measurements that could be indicative of liver abscesses (LA) in weaned beef × dairy cross steers. Beef × dairy cross steers [n = 40; initial body weight (BW) = 120 ± 12 kg] were sourced from a local dairy calf ranch and transported 166 km to the USDA-ARS Livestock Issues Research Unit Liberty Farm near Lubbock, TX (d -16). Calves were initially housed outside in soil-surfaced pens for 16 d with ad libitum access to water and high-forage receiving diet before being moved into individual pens within an environmentally controlled barn (d 0). While housed in the barn, calves were cycled between a high-forage diet (2 d) and a high-concentrate finishing diet (3 d) for 3 cycles. Additionally, calves were administered Fusobacterium necrophorum subsp. necrophorum (4.25 x 106 CFU in 100 mL) and Salmonella enterica serotype Lubbock (1.29 x 106 CFU in 100 mL) intraruminally on d 0, 5, and 10. Following the last inoculation on d 10, calves were fed the high concentrate finishing diet for the remainder of the study. Whole blood samples for measurement of complete blood counts were collected via jugular venipuncture on d 0, 10, 21 and 30. On d 31, calves were harvested to determine LA prevalence. Fifty percent of calves developed at least one LA. Complete blood count analysis revealed day effects (P ≤ 0.03) for all variables, with the exception of basophil percentage (P = 0.06; Table 1). Prevalence of a liver abscess was associated with increased (P < 0.01) neutrophil count, neutrophil:lymphocyte ratio, and neutrophil percentage, concomitant with decreased (P ≤ 0.04) lymphocyte percentage, and monocyte percentage. Additionally, a tendency (P = 0.09) was observed for decreased red blood cells in calves with a LA compared with those without. These data suggest that changes in neutrophil and lymphocyte concentrations within the blood may be indicative of LA prevalence in beef × dairy steer calves and hold potential as predictive markers for LA.