摘要：

Forty-eight steer calves (initial BW = 314 ± 21 kg), housed on pasture with their dams, were used to document changes in growth performance and various physiological measures when fitted with (YD) or without (ND) an antisuckling device for 7 d and weaned (d 0) by fenceline (FS) or total separation (TS). All steers were weighed and bled on d 7, 4, 0, 3, 7, 14, and 35. On d 7 the FS group was moved to a pasture lot distant from their dams and adjoining the TS group. Weight gain was similar (P = 0.74) between ND and YD steers between d 7 and 0. The YD-FS steers lost weight (P = 0.01) by d 3 compared with the YD-TS steers, and from d 14 to 35 the YD-TS steers were heavier (P = 0.02) than the YD-FS steers. Hematocrit (HCT) increased (P = 0.04) in YD but not ND steers by d 4 and was similar between treatments thereafter. Before weaning, treatment had no effect on neutrophil-to-lymphocyte ratio, plasma cortisol, haptoglobin, ceruloplasmin, or serum interferon-γ (IFN-γ) concentrations. Plasma haptoglobin and ceruloplasmin increased (P < 0.01) in all steers from d 7 to 4. Upon weaning, d 3 ceruloplasmin was greater (P < 0.05) in FS vs. TS steers, d 7 plasma cortisol was greater (P < 0.05) in YD-FS vs. YD-TS steers, and d 14 IFN-γ was greater (P < 0.05) in TS vs. FS steers. Lymphocyte percentage tended (P < 0.10) to be lower for YD vs. ND steers on d 0 to 7 regardless of method of separation, resulting in an overall greater (P < 0.05) mean neutrophil-to-lymphocyte ratio for the YD steers. Use of a preweaning anti-suckling device marginally altered growth performance and physiology in beef steers postweaning.

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