NUTRITIONAL EFFECTS ON NEUROTRANSMITTER METABOLISM IN THE BROILER CHICKEN

Two experiments were conducted with broiler chickens to determine vari ous nutritional effects on neurotransmitter metabolism. In Experiment 1, 21-day old chickens were fasted for 24 hr, fed on an ad libitum bas is, fed a diet containing 450 g crude protein/kg (high-protein) or fed a diet containing 80 g crude protein/kg (high carbohydrate) to examin e nutritional regimens that may alter neural factors regulating growth . Chickens were injected (250 mg/kg BWt) with a tyrosine hydroxylase i nhibitor, alpha-methyl-DL-rho-tyrosine (AMPT), to inhibit catecholamin e synthesis and to estimate turnover constants as functions of these t reatments. In Experiment 2, 7-day old chickens were fed diets containi ng 120, 180, 240 and 300 g crude protein and 1 mg T-3/kg diet for 21 d ays to determine the effects of both dietary protein and thyroid statu s on catecholamine concentrations. Norepinephrine (NE) and dopamine (D A) in the brains and NE and DA in the hearts and pancreases were separ ated by HPLC and determined by electrochemical detection. Fractional t urnover of DA in the brains of both fed and fasted chickens was equal but was over twice as great as that of NE. Fractional NE turnover in h earts of both fed and fasted chickens was 12.3%/hr although fractional NE turnover in pancreas was greater (P < 0.05) in fasted than in fed chickens (9.0%/hr vs 5.1%/hr). These same rate constants were also see n in brains of chickens fed high-carbohydrate or high-protein diets. I n contrast, a protein diet increase pancreatic and cardiac NE turnover compare to a high-carbohydrate diet.