|Matteri, Robert - Bob|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/1/2001
Publication Date: N/A
Citation: Interpretive Summary: Increasing voluntary feed intake would positively impact animal growth, milk production and reproductive efficiency. Orexin-A and orexin-B are two closely-related, naturally-occurring brain compounds that are involved in stimulating appetite in rodents. We produced synthetic orexin-B in order to determine whether Orexins were effective regulators of feed intake in livestock. Orexin-B was injected into the brains of sheep and found to significantly increase feed intake over a 4-hour period. These results identify a brain peptide that may be an important regulator of appetite in ruminants (sheep, cattle). Information on the efficacy and biological significance of regulators such as orexin is needed to develop practical methods of improving feed intake and related productivity. These findings will be utilized by scientists in academia, government and biotechnology industry.
Technical Abstract: Orexin is a hypothalamic neuropeptide that regulates feeding behavior in rats. Orexin-B has recently been cloned in pigs and was shown to stimulate food intake after intramuscular injection. This study was designed to determine whether intracerebroventricular (icv) and intravenous (iv) injections of orexin could regulate appetite in sheep. Suffolk wethers were moved to indoor facilities 2 wk before having icv cannulas installed. Sheep were monitored over a 2-h control period prior to iv injection with saline or porcine orexin-B (3 ug/kg BW) or icv injection with artificial cerebrospinal fluid (CSF), orexin-B (0.03, 0.3 or 3 ug/kg BW) or in a second experiment with either orexin-B (0.3 ug/kg BW), neuropeptide Y (NPY; 0.3 ug/kg BW) or orexin plus NPY. Food intake was monitored for consecutive 2-h periods. The iv injections of orexin had no effects on food intake or on metabolite or hormone concentrations. In icv sheep, there was a treatment effect of orexin on food intake at 2 (P<0.04) and 4 (P<0.02). In the comparison with NPY, orexin had a similar effect to NPY in the first 2 h after injection (.23 kg for orexin and .2 kg for NPY). The combination of NPY and orexin had a greater effect on food intake (to .34 kg) than orexin (P<0.04) or NPY (P<0.007) alone. Differences were not apparent in the subsequent 2-h interval. There were no differences in free fatty acid or glucose concentrations following orexin injection. There was an effect of icv orexin treatment on plasma cortisol concentrations (P<0.001). Cortisol was increased by orexin in the 0-2 h (P<0.008) but not in the 2-4 h (P<0.08) intervals after orexin injection. These data indicate that central administration of orexin stimulates feed intake in sheep.