Influence of preshipment management on the adrenal response of beef calves to ACTH before and after transit.

The influence of preshipment management, transit (965 km) and postshipment management upon the ability of the adrenal gland to respond to exogenous adrenocorticotropic hormone (ACTH) was evaluated in 60 beef calves (47 bulls and 13 steers). Adrenal response to ACTH treatment was quantified before shipment (PRE), about 24 h (POST) and 3 wk after transit (3 WK). Calves were assembled for 4 or 10 d before shipment and fed either a hay or a high energy diet (HE). The area under the plotted curve for the plasma corticoid concentration response to ACTH was used as an adrenal response test (ART). The feeding of hay during the first 4 d of assembly resulted in a greater (P less than .05) PRE ART value than feeding of the HE diet, but after 10 d of assembly, the ART was similar for animals on the two diets. The ART at 24 h after transit was similar to that before shipment. The HE group had a greater (P less than .05) ART than the hay group 3 wk after arrival, however, values were dependent upon postshipment management. Placement of calves on winter wheat pasture soon after arrival resulted in greater ART (P less than .05) values after the 3 wk recovery period than for calves that grazed native range for 10 or 20 d before grazing winter wheat pasture. These data indicate that the ability of the adrenal gland to respond to ACTH is increased at preshipment if the assembly period is 4 d compared to 10 d and the adrenal response at 3 wk after arrival is greater if a HE diet is fed during assembly instead of hay.