COSINOR ANALYSIS OF FEED-INTAKE CYCLE OF RATS FED A ZINC-DEFICIENT DIET AND THE EFFECT OF ZINC SUPPLEMENTATION

Rats fed a Zn-deficient diet develop a characteristic cyclic variation in feed intake (Mills et al., Am J Clin Nutr 22: 1240-1249 (1969)). A preliminary analysis (Tamaki et al., Br J Nutr 73: 711-722 (1995)) of the cyclic variations was followed with a personal computer. Cosinor analysis revealed that the cyclic period of the feed intake of male ra ts was 3.5+/-0.05 d. The mesor, amplitude and acrophase value were 10. 0+/-0.3 g/d, 4.4+/-0.2 g/d and 3.5+/-0.3 radian, respectively. The cyc le of body-weight change of the Zn-deficient rats was well synchronize d with that of feed intake. The parameters of the feed intake cycle ha d a high correlation to the corresponding parameters of body-weight ch ange (mesor: r=0.846; amplitude: r = 0.771; period: r = 0.925; acropha se: r = 0.452). With the supplementation of Zn (0.95-3.80mg/kg of the Zn-deficient diet), cyclic variations in feed intake and body-weight c hange were also found. The mesor, amplitude and period of feed intake cycle were in good correlation with Zn intake (r = 0.856, p < 0.001, r = - 0.804, p < 0.001 and r= 0.613, p < 0.01, respectively). The cycle of feed intake of the rats fed a Zn-free diet was simulated to be: me sor 9.7+/-0.1 g/d, amplitude 6.5+/-0.1 g/d and period 3.4+/-0.02 d. Th e concentration of Zn intake given the half-maximal value of the ampli tude was assumed to be 56+/-1 mu g/d.