305 Effects of zinc or copper deficiency and pair - feeding on hepatic leptin mRNA expression

s of papers 71 307 Broilers compared to Leghorns show an imbalance of the autonomic nervous system. W.J. Kuenzel*1 and R. Grossmann2, 1University of Maryland, College Park, MD/USA, 2Institute of Animal Science and Behavior, Celle,Germany. The following experiment tested the hypothesis that the parasympathetic nervous system (PNS) of broilers dominates over the sympathetic nervous system (SNS) as a consequence of intense genetic selection for increased growth rate (Kuenzel,W. 1994. J. Nutr. 124:1355S). Twenty broiler and 20 Leghorn chicks were anesthetized and surgically implanted with two catheters. One was inserted into the brachial vein for injection of drugs in an awake bird. The second was chronically implanted into the sciatic artery for measuring blood pressure (BP). Drugs injected included methacholine chloride (MC), a cholinergic agonist; norepinephrine (NE),an adrenergic neurotransmitter; propranolol (PR), a β adrenoceptor antagonist; and atropine (AT), a cholinergic receptor antagonist. No differences were found in resting BP between broilers and Leghorns. When the SNS was blocked by PR, no differences were detected in the amount of BP change elicited by MC. In contrast, when the PNS was blocked by AT, the Leghorn cockerels exhibited nearly a 51% greater increase in BP following NE administration compared to broiler cockerels. Results suggest that the response of the SNS is attenuated and the tone of the PNS is significantly enhanced in broilers compared to Leghorns. It is recommended that an attempt be made by poultry geneticists to bring back into balance the autonomic nervous system of broilers.