296 Effects of corticotropin-releasing hormone (CRH) and vasopressin (VP) challenge duration on complete blood count and serum metabolites of growing beef cattle

摘要

The objective was to evaluate stress challenge and duration on immunologic and metabolic variables of growing beef cattle. Thirty crossbred steers were used in a randomized complete block design. Treatments were i.v. injection of: 1) Control (3 mL saline for 4 consecutive days: n = 10), 2) Acute (0.3 µg/kg BW CRH and 1.0 µg/kg BW VP for 1 day, saline for 3 consecutive days; n = 10), or 3) Chronic (0.3 µg/kg BW CRH and 1.0 µg/kg BW VP for 4 consecutive days; n = 10) at hour 0, 24, 48, and 72. Rectal temperature and serum were collected at hour 0, 1, 2, 24, 25, 26, 48, 49, 50, 72, 73, 74, 144, and 336 for analysis of cortisol and serum metabolites. Whole blood was collected at hour 0, 24, 48, 72, 144, and 336 for analysis of complete blood count. Data were analyzed using the MIXED procedure of SAS. Rectal temperature tended to be greater for stress challenged cattle (stress vs. no; P = 0.06). Cortisol was greater for cattle receiving acute and chronic than control at hour 1 and greater for chronic than both acute and control at hour 25, 26, 49, 50, 73, and 74 (P ≤ 0.01). Similarly, serum glucose concentration was increased at hour 1 for acute and chronic and chronic had greater glucose at hour 25, 49, 50, 73, and 74 (P ≤ 0.04). Potassium was less for acute and chronic at hour 1 and 2 and chronic was less than acute and control at hour 24, 25, 26, 49, 50, 73, and 74 (P ≤ 0.02). Chronic had greater (P = 0.04) white blood cell count than control at 72 h. Monocyte concentration was least at hour 144 for chronic (P < 0.01). Results demonstrate that stress influences cortisol, glucose, electrolyte, and white blood cell concentrations.