Effect of different levels of dietary zinc supplementation on body weight and learning ability in rats

To investigate the effect of increasing dietary zinc supplementation on body weight and learning ability in rats.Zinc supplemental diet contained 200, 400, 600, 800 or 1 600 mg/kg zinc,respectively.Y-labyrinth test was applied to exam the learning and memory function of rats.Significantly greater weight gain was observed in rats fed with 400 mg/kg zinc diet than in rats fed with 200 mg/kg zinc diet(P<0.05). During the early experiment, lower weight increments were notably observed in rats with 600, 800 or 1 600 mg/kg zinc supplementation than that in control group, respectively. But the influence on weight relief became weaker in pace with time on the whole. Learning and memory function for rats were strikingly improved at level of 200 mg/kg zinc diet compared with the control level(P<0.05), and were damaged in varying degrees at higher(except 1 600 mg/kg) zinc supplementation levels in feeds, among which,800 mg/kg zinc dosage had produced obviously lesion for learning ability in rats compared with normal, 200 or 1 600 mg/kg zinc levels(P<0.05, respectively).[Conclusion]These results suggest that different levels of zinc supplementation have some incompletely parallel effects on the growth, memory and capacity to learn in rats.