Forty-eight steer calves (initial BW = 314 Â± 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-Î³ (IFN-Î³) 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-Î³ 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.
Key words: beef cattle, fenceline contact, physiology, performance, 2-stage weaning
The weaning of beef cattle involves separation of calves from their dams. Upon weaning, calves are either relocated to an adjoining pasture for a brief period (fenceline contact), which prevents them from nursing but allows some social contact with their dams, or separated from dams at a distance, which prevents any direct contact. Calves weaned by abruptly moving them to a distant pasture exhibit greater signs of distress, as evidenced by increased movement and vocalization and decreased food consumption compared with calves provided temporary fenceline contact (Stookey et al., 1997; Price et al., 2003). Price (2008) attributed these behavioral indices to the loss of social contact between the cow-calf pair and the denial of suckling.
Calves weaned in 2 stages by initially preventing them from nursing for a brief period (stage 1) and then separating them from their dam (stage 2) are reported to be less distressed compared with calves weaned using the abrupt method based on behavioral data (Haley et al., 2001, 2005). Research documenting physiological changes of weaning-associated stress is limited to the effects of abrupt versus no separation of cow-calf pairs (Lefcourt and Elsasser, 1995; Hickey et al., 2003). The objective of the experiment was to examine performance and physiological responses in beef steer calves weaned using a 2-stage weaning process compared with an abrupt weaning process.
MATERIALS AND METHODS
Animals and Experimental Design
All animal procedures were reviewed and approved by the
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