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 rats was 3.5±0.05 d. The mesor, amplitude and acrophase value were 10.0±0.3g/d, 4.4±0.2g/d and 3.5±0.3 radian, respectively. The cycle of body-weight change of the Zn-deficient rats was well synchronized with that of feed intake. The parameters of the feed intake cycle had a high correlation to the corresponding parameters of body-weight change (mesor: r=0.846; amplitude: r=0.771; period: r=0.925; acrophase: 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 change were also found. The mesor, amplitude and period of feed intake cycle were in good correlation with Zn intake (r-0.856, p