Effects of corticotrophin releasing hormone and vasopressin challenge duration on hematologic, metabolic, and rumen fermentation parameters of growing beef steers

Authors: GEESLIN, MEAGAN - West Texas A & M University; RICHESON, JOHN - West Texas A & M University; HERNANDEZ-GIFFORD, JENNIFER - New Mexico State University; SOTO-NAVARRO, SERGIO - New Mexico State University; Sanchez, Nicole; SAMUELSON, KENDALL - West Texas A & M University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Multiple stressors that cattle experience during the transition from the ranch of origin to the feedlot can lead to chronic stress. Because there is an association between stress, nutrition, and animal health, it is important to understand how length of stress exposure affects responses linked to growth and health. Therefore, a study was conducted with USDA-ARS scientists and university collaborators to test the effects of acute (short term) or chronic (repeated) stress on immune and metabolic factors in beef steers. Results from this study indicate that chronic stress altered white blood cells, stress hormones, and metabolic factors. Also, the liquid passage rate of steers was least in steers exposed to chronic stress. These data suggest a negative effect of repeated or chronic stress on immunity and metabolism in steers. These data will be of interest to scientists in the field of stress physiology as well as cattle producers.

Technical Abstract: The objective of this study was to evaluate stress challenge duration on hematologic, metabolic, and rumen fermentation parameters of beef steers. Thirty steers (416 ± 19 kg) were used in a randomized complete block design with 2 blocks and 3 treatments. Steers were housed individually for 14 d of adaptation and a 14- d collection period, for a total of 28 d. Treatments were intravenous injection of: 1) Saline at 0, 24, 48, and 72 h (n = 10; Control); 2) Corticotropin releasing hormone (CRH) and vasopressin (VP) injection at 0 h and saline at 24, 48, and 72 h (n = 10; Acute]; or 3) CRH and VP injection at 0, 24, 48, and 72 h (n = 10; Chronic). Serum samples were collected at 0, 1, 2, 24, 25, 26, 48, 49, 50, 72, 73, 74, 144, and 336 h for analysis of cortisol, insulin, and serum chemistry. Additionally, whole blood and serum were collected at 0, 24, 48, 72, 144, and 336 h for analysis of complete blood count and non-esterified fatty acids (NEFA), and ruminal fluid was collected via oral lavage at 0, 72, 144, and 336 h to evaluate volatile fatty acid (VFA) composition. Cortisol was greater (treatment × hour P = 0.01) for cattle receiving acute and chronic treatments than control at 1 h and greater for chronic than both acute and control at 25, 26, 49, 50, 73, and 74 h. Similarly, there was a treatment × hour interaction (P = 0.01) for serum glucose concentrations where cattle receiving acute and chronic treatments had greater glucose at 1 h than control, and cattle receiving chronic treatment had greater glucose at 25, 49, 50, 73, and 74 h than acute and control treatments. Serum insulin concentrations were greater (treatment × hour P = 0.01) in chronic and acute treatments than control at 1 h and greater for chronic compared to acute and control treatments at 25, 49, and 73 h. There was a treatment × hour interaction (P = 0.003) for total white blood cell count such that chronic had greater concentration than control treatment at 72 h. Conversely, monocyte concentration was less for chronic than acute and control treatments at 144 h (treatment × hour interaction P = 0.01), and eosinophil concentration was greater for chronic than control treatment from 48 to 114 h (treatment × hour interaction P = 0.02). Serum NEFA tended (P = 0.09) to be greater in stressed cattle compared to control cattle. Minimal differences were observed in VFA concentrations with the exception of acetate, which was least for chronic, intermediate for control, and greatest for acute treatment at 72 h (treatment × hour interaction P = 0.05). These results demonstrate that administration of CRH and VP affects complete blood count and serum chemistry, but the duration of exposure does not diminish the physiological response to a stress challenge.