Location: Livestock Issues ResearchTitle: Serum blood metabolite response and evaluation of select organ weight, histology and cardiac morphology of beef heifers exposed to a dual corticotropin-releasing hormone and vasopressin challenge following supplementation of Author
|Buntyn, Joe - University Of Nebraska|
|David, Steffen - University Of Nebraska|
|Sieren, Sarah - University Of Nebraska|
|Jones, Steve - University Of Nebraska|
|Erickson, Gaylean - University Of Nebraska|
|Carroll, Jeffery - Jeff Carroll|
|Schmidt, Ty - University Of Nebraska|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2017
Publication Date: 12/8/2017
Citation: Buntyn, J.O., David, S., Sanchez, N.C., Sieren, S.E., Jones, S.J., Erickson, G.E., Carroll, J.A., Broadway, P.R., Schmidt, T.B. 2017. Serum blood metabolite response and evaluation of select organ weight, histology and cardiac morphology of beef heifers exposed to a dual corticotropin-releasing hormone and vasopressin challenge following supplementation of. Journal of Animal Science. 95:5327-5338.
Interpretive Summary: Zilpaterol hydrochloride (ZH) is a ß2 – adrenergic receptor agonist (ß2-AA) that is approved for the use in feedlot cattle in Mexico, South Africa, and the United States. In September 2013, the supplementation of ZH was implicated as a possible cause of reported lameness at harvest. Another report demonstrated an epidemiologic risk of mortality associated with ZH supplementation during the late feeding period, but did not investigate the cause of the mortality. Furthermore, limited controlled studies have investigated the impact of ZH supplementation on organ morphology. Therefore, the objective of this trial was to evaluate the impact of ZH supplementation on blood chemistry concentrations and internal organ weight and morphology of feedlot heifers at harvest. Overall, the results from this study indicated that there was a tendency for liver and kidney weights as a percent of body weight to be in ZH supplemented cattle. However, other organ (i.e., heart, lung, adrenals) to BW ratios remained similar between the two groups. These data suggest that there are some variations observed between treatments in terms of response to ZH supplementation and the stress challenge; however, in the environmental conditions of this study, limited variation in blood metabolic responses and organ weights suggests that the supplementation of ZH did not detrimentally alter the physiology of cattle. This study represents a collaborative effort among scientists from the University of Nebraska and the USDA Agricultural Research Service's Livestock Issues Research Unit in Lubbock, Texas. This information will be of importance to beef cattle feedlot producers, veterinarians, and researchers evaluating the effects of beta-agonists on beef cattle health and well-being.
Technical Abstract: The objective of this study was to: 1) determine if supplementation of Zilpaterol Hydrochloride (ZH) altered select organ weights, histology and cardiac anatomical features at harvest and 2) determine if administration of a corticotropin-releasing hormone (CRH) and vasopressin (VP) challenge following 20 d ZH supplementation altered the blood chemistry profile in cattle. Crossbred heifers (n = 20; 556 ± 7 kg BW) were randomized into two treatment groups: 1) Control (CON): no ZH, and 2) Zilpaterol [ZIL; ZH at 8.33 mg / kg (DM basis) for 20 d]. On d 20 of supplementation, heifers were fitted with indwelling jugular catheters. On d 24, starting at 0800h and continuing until 1600h, blood samples were collected at 60-min intervals. At 1000h, heifers received an i.v. bolus of CRH (0.3 µg / kg BW) and VP (1.0 µg / kg BW) to activate the stress axis. Serum was separated and stored at -80oC until analyzed for a large animal chemistry panel. Following the CRH/VP challenge, heifers were harvested on d 25, 26, and 27 (5, 6, and 7 d post-ZH supplementation); BW, HCW, select organ weights, histology, and total heart necropsy were performed. A treatment effect (P = 0.02) was observed for Ca, K, creatinine, alkaline phosphatase and sorbitol dehydrogenase. Zilpaterol heifers had decreased concentrations of Ca and K and increased concentrations of creatinine (P = 0.02) during the CRH/VP challenge, when compared to CON heifers. Control heifers had greater (P = 0.05) alkaline phosphatase and sorbitol dehydrogenase concentrations when compared with ZIL heifers. A treatment x time interaction (P = 0.02) was observed for P; concentrations were similar between treatments from -2h to 6h post-challenge; 7 h post-challenge CON heifers had decreased P compared to ZIL. Liver (P = 0.06) and kidney (P = 0.08) weights as a percent of BW tended to be reduced in ZIL heifers. Gross liver weights tended (P = 0.08) to be less in ZIL heifers. Other organ (heart, lung, adrenals) to BW ratios remained similar (P = 0.41). These data suggest that there are some variations observed between treatments in terms of response to ZH supplementation and the CRH/VP challenge; however, in the environmental conditions of this study, limited variation in blood metabolic responses and organ weights suggests that the supplementation of ZH did not detrimentally alter the physiology of cattle.