|Bernhard, Bryan -|
|Rathmann, Ryan -|
|Finck, Derek -|
|Jennings, M -|
|Young, Tanner -|
|Johnson, Bradley -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2012
Publication Date: October 9, 2012
Citation: Bernhard, B.C., Sanchez, N.C., Rathmann, R.J., Carroll, J.A., Finck, D.N., Jennings, M.A., Young, T.R., Johnson, B.J. 2012. Chromium supplementation alters both glucose and lipid metabolism in feedlot cattle during the receiving period. Journal of Animal Science. 90:4857-4865. Interpretive Summary: This research represents a collaborative effort by scientists from Texas Tech University and the Livestock Issues Research Unit to determine the influence of supplementing newly-received cattle with chromium on the response to a glucose tolerance test and an insulin sensitivity test. Newly received cattle in a feedlot are exposed to stress due to weaning, marketing, and handling associated with transportation events. Stress has been demonstrated to increase the loss of chromium. Yet, studies in which additional chromium has been supplemented in the diet have demonstrated favorable effects on performance including average daily gain. Additionally, studies suggest that chromium supplementation may have beneficial effects on glucose metabolism. Chromium has been demonstrated to amplify insulin signalling through binding to the insulin receptor as part of a component called chromadulin. Therefore, we utilized newly received beef steers to determine the effect of supplementing chromium as chromium propionate on glucose and lipid metabolism. Data from this study suggest that supplementing chromium to the basal diet can alter insulin production and glucose and lipid metabolism of newly received steers. Specifically, insulin concentrations remained elevated in chromium supplemented steers following glucose infusion, while glucose and non-esterified fatty acid concentratiosn remained lower before and after glucose infusion compared to control steers. In response to insulin infusion, chromium-supplemented steers had greater glucose concentrations, and maintained lower non-esterified fatty acid concentrations throuhout the challenge compared to control steers. These data suggest that chromium-supplemented steers have have more glycogen available for energy, which prevented the steers from having to mobilize stored lipids. This data will be of interest to scientists in the fields of stress physiology, nutrition, and metabolism as well as cattle producers, and can be used to enhance performance of newly-received feedlot cattle.
Technical Abstract: Crossbred steers (n = 20; 235 +/- 4 kg) were fed 53 days during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brandChromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (Con) or 0.2 miligram/kilogram of Cr to the total diet on a dry matter basis. Cattle were fitted with jugular catheters on day 52. A glucose tolerance test (GTT) and an insulin sensitivity test (IST) were conducted on day 53 by infusing the steers with 1 mililiter of a 50% glucose solution/kilogram of body weight (Dextrose 50%, Durvet, Inc.) at 0900 h and 0.1 IU of bovine insulin/kilogram of body weight at 1400 h, respectively. Blood samples were collected at -60, -45, -30, -15, 0, 7.5, 15, 30, 45, 60, 90, 120, and 150 minutes relative to each infusion. Serum was isolated to determine glucose, insulin, and non-esterified fatty acid (NEFA) concentrations. Data were analyzed using the Mixed procedure of SAS with each steer serving as the experimental unit and fixed effects of treatment, time, and their interaction. Throughout the GTT no differences were detected in glucose concentrations, glucose clearance rates (k), or pre-infusion insulin concentrations (P > 0.50), but insulin concentrations post-infusion tended to be greater for the Cr-supplemented steers (P = 0.06). This caused an increase in the insulin to glucose ratio (I:G) from 0 to 150 minutes post-infusion for the Cr-supplemented steers (P = 0.03). In addition, NEFA concentrations during the GTT were lower (P = 0.01) for Cr-supplemented steers both pre- and post-infusion. During the IST there was no treatment effect on glucose concentrations pre-infusion (P = 0.38), but post-infusion glucose concentrations were greater (P < 0.01) in the Cr-supplemented steers. The k of Cr-supplemented steers tended to be faster than Con steers from 30 to 45 miutes post-infusion (P = 0.06). During the same test, there was no treatment effect detected for insulin concentrations (P > 0.33), but at 7.5 minutes there was a trend for the insulin concentrations of the Con steers to reach a higher peak (P = 0.12). The I:G were not affected by treatment (P > 0.40). Concentrations of NEFA were reduced (P < 0.01) both pre- and post-infusion during the IST for Cr-supplemented steers. Results of this study indicate that supplementation of Cr to the basal diet can alter insulin production and glucose and lipid metabolism of newly received steers. Suggesting that Cr-supplemented steers may have more glycogen available for energy and do not need to mobilize as much stored adipose tissue.