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ghrelin infusion, plasma growth hormone, dry matter


Six steers (915 ± 37.8 kg) were used in a crossover design to determine the effects of intravenous infusion of bovine ghrelin (BGR) on plasma growth hormone (GH) concentrations, length of time spent feeding, and dry matter disappearance per unit of metabolic weight. Steers were fed individually once daily (0800 h) and allowed to consume ad libitum until 2000 h when feed was removed. Daily feed allotment was sufficient to result in ≥ 10% feed refusal. Serial blood samples were collected from steers fitted with an indwelling jugular catheter at 15-min intervals from 0600 h through 1800 h. Harvested plasma was assayed for ghrelin and GH concentrations. Saline (SAL) or BGR was infused via jugular catheter at 1200 h and 1400 h. Treatment infusion times were selected on the basis of the observation that steers did not consistently feed at these times. Exogenous BGR was infused to achieve a plasma concentration of 1000 pg/mL. This dosage was chosen on the basis of previous research that indicated a peak ghrelin concentration of 1000 pg/mL for fasting steers. Steers were allowed 5 d to adjust between treatment periods and then treatments were switched between steer groups and the sampling period repeated. Compared to SAL steers, average plasma ghrelin concentration was elevated (P ≤ 0.0001) at the first post-infusion sampling for BGR steers at both infusion. Bovine ghrelin infusion resulted in elevated (P ≤ 0.005) plasma GH concentrations compared to SAL steers after the first infusion. The second infusion of BGR resulted in numerically higher GH concentrations, but this difference was not statistically different from SAL steers or baseline concentrations. Both plasma ghrelin and GH concentrations returned to baseline 30 min post-BGR infusion. Length of time spent feeding (P = 0.03) and dry matter disappearance per unit of metabolic body weight (P = 0.05) for the combined infusion times were increased for steers infused with BGR. Bovine ghrelin is a compound that has the potential to elevate plasma GH concentrations and to increase length of time spent feeding and dry matter disappearance per unit of metabolic body weight.

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South Dakota State University


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