Comparative stress responses to short transport and related events in Hereford and Brahman steers

Abstract

Three summer experiments compared responses to transportation-related events in 2- to 4-yr-old Brahman (Bos indicus) and Hereford (B. taurus) steers. In Exp. 1, steers were hauled round-trip (4 h) or fasted in holding pens. Transport transiently increased (P < 0.01) plasma cortisol and glucose concentrations, decreased (P < 0.05) plasma triglyceride concentrations, and increased total leukocyte counts. Blood constituents were not altered for steers fasting in holding pens. Treatment-day BW shrink was greater (P < 0.01) in transported steers than penned steers. Blood constituent responses were unaffected (P < 0.05) by subspecies. Hereford experienced greater (P < 0.05) transport-day BW shrink than Brahman across treatments. Steers in Exp. 2 were hauled to a new farm for a 1-wk relocation period or hauled round-trip an equal time (0.67 h) and returned to the home station. Both treatments similarly experienced transport-day BW shrink and increased (P < 0.01) plasma cortisol and glucose. Subspecies did not affect (P < 0.05) blood constituent responses to transport. Hereford experienced greater (P < 0.05) transport-day shrink than Brahman. Relocation did not elicit (P < 0.05) changes in blood profiles beyond the day of transport. In Exp. 3, steers were loaded and unloaded without transport, transported round-trip (1 h), or fasted in a holding pen for 3 h. Cortisol increased (P < 0.01) after transport and after loading/unloading. Leukocytes and glucose increased (P < 0.01) after the 1 h transport. Steers transported experienced greater treatment-day BW shrink than those fasted or loaded and unloaded (P < 0.01; -3.13 vs. -1.36 and -0.35 ± 0.76%, respectively). The subspecies did not vary (P < 0.05) for blood constituent responses or shrink in Exp. 3. Animal responses were not evident 24 h after treatments in each experiment. In summary, transport caused stress, but Brahman steers were not more sensitive than Herefords. Hereford steers were susceptible to greater transport BW shrink than Brahman under the summer conditions.