Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle

• Published in: Journal of animal science Vol. 84; no. 12; pp. 3285 - 3300
• Main Authors: Wertz-Lutz, A.E, Knight, T.J, Pritchard, R.H, Daniel, J.A, Clapper, J.A, Smart, A.J, Trenkle, A, Beitz, D.C
• Format: Journal Article
• Language: English
• Published: Savoy, IL American Society of Animal Science 01.12.2006; Am Soc Animal Sci
• Subjects: Animal Nutritional Physiological Phenomena; Animal productions; Animals; beef cattle; Biological and medical sciences; blood chemistry; blood glucose; Blood Glucose - drug effects; blood plasma; Cattle; cattle feeding; Circadian Rhythm; Cross-Over Studies; dry matter intake; duration; energy balance; Fatty Acids, Nonesterified - blood; feed deprivation; feed intake; feeding behavior; Feeding Behavior - physiology; Food Deprivation; free fatty acids; Fundamental and applied biological sciences. Psychology; Ghrelin; Growth Hormone - blood; ingestion; insulin; Insulin - blood; Male; nutritional status; Peptide Hormones - blood; Peptide Hormones - pharmacology; somatotropin; steers; Terrestrial animal productions; Vertebrates; Hormone; Farming animal; Feeding behavior; Animal feeding; Growth; feed intake; cattle; Concentration; ghrelin; Influence; Livestock; growth hormone; Nutritional status
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2006-053

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 ± 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 ± 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 ± 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 ± 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 μg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.