This is a draft schedule. Presentation dates, times and locations may be subject to change.

446
Hematological Variables Are Influenced By Vaccine Antigen Type and Acute or Chronic Stress Model in Beef Calves

Tuesday, July 11, 2017: 12:00 PM
314 (Baltimore Convention Center)
Rachel E. Hudson, West Texas A&M University, Canyon, TX
Dexter J. Tomczak, West Texas A&M University, Canyon, TX
Emily L. Kaufman, West Texas A&M University, Canyon, TX
Ashlee M. Adams, West Texas A&M University, Canyon, TX
Jeffery A. Carroll, USDA-ARS, Livestock Issues Research Unit, Lubbock, TX
P. Rand Broadway, USDA-ARS, Livestock Issues Research Unit, Lubbock, TX
Michael A. Ballou, Texas Tech University, Lubbock, TX
John T. Richeson, West Texas A&M University, Canyon, TX
The objective was to determine the effect of replicating and non-replicating vaccine antigens administered to acutely or chronically stressed beef calves on hematologic and endocrine responses. A total of 48 crossbred beef steers (d 0 BW = 226 ± 6.2 kg) from a single ranch origin were used in a 2 × 2 factorial to evaluate main effects of stress, vaccine type and their interaction; resulting in 4 treatments (n=12/treatment) consisting of acute stress with killed virus vaccination (ACUKV), ACU with modified-live virus vaccination (ACUMLV), chronic stress with KV (CHRKV), and CHR with MLV (CHRMLV). The ACU treatments were weaned at their origin ranch on d -37 and transported 472 km to the study site near Canyon, TX on d -21 to allow acclimation. The CHR treatments were weaned on d -3, transported 460 km to a facility near Lubbock, TX on d -2, and relocated 164 km to the study site on d -1. Vaccine treatments were administered on d 0 and KV was revaccinated on d 14. Animal was experimental unit and dependent variables were analyzed using PROC MIXED with repeated measures (d). Hematological variables were determined from whole blood collected on d -2, 0, 1, 3, 5, 7, 14, and 21 via automated hemocytometer. Cortisol concentration was determined using ELISA from serum collected on d -2, 0, 1, 3, 5, and 7. Total leukocytes were not different on d -2 (P=0.66), but were lesser for CHR vs. ACU on d 0, 1, 3, 5, 7, 14 and 21 (P≤0.02). Vaccine type also affected total leukocytes; leukocytes were decreased for MLV on d 5, 7, and 14 (P≤0.04) compared to KV. Neutrophils (2.01 vs. 3.83 K/µL) and neutrophil:lymphocyte (0.27 vs. 0.67) were markedly increased (P<0.001) for CHR on d -2; conversely, neutrophils were decreased (P≤0.007) on d 1 and 21 for CHR. Monocytes were decreased on d 1, 5 and 7 for MLV (P≤0.04) and d -2 to 14 for CHR (P≤0.03). Eosinophils were reduced (P=0.007) for CHR (0.097) vs. ACU (0.176 K/µL) on d -2; however, a rebound response (P=0.03) was noted on d 0 such that eosinophils were 0.288 and 0.160 K/µL for CHR and ACU, respectively. Serum cortisol was greater (P≤0.04) for ACU on d -2 to 5, suggesting suppression of endocrine activity in CHR over time. Results indicate this CHR stress model and MLV vaccination may have more profoundly induced immunosuppression in beef calves.