Effects Of Zinc-Bearing Zeolite-Clinoptilolite On Digestive Function, Metal Deposition And The Expression Of Zinc Transporter Gene Of Laying Hens

This experiment was conducted to study the effects of zinc-bearing zeolite-clinoptilolite (ZnCP) on digestive enzyme activity, nutrient digestibility, egg quality, metal contents in various tissues, activities of zinc-containing enzymes in liver and the expression of zinc transporter gene of laying hens. The study included three trials and the results are presented as follows:The first trial was conducted to study the effects of ZnCP on nutrient digestibility, digestive enzyme activity and egg quality of laying hens. A total of 450 30-wk-old Hyline Brown laying hens were randomly allotted to five dietary treatments with six replicates. The birds were fed a basal diet containing 80 mg/kg Zn from ZnSO4 or 20,40,60 or 80 mg/kg Zn from ZnCP at the level of 0.11%,0.23%,0.34% or 0.46%, respectively. The results showed that compared with the control group, the supplementation of 0.34% ZnCP significantly improved the digestibility of CP and EE (P<0.05); the supplementation of 0.23% ZnCP significantly improved the activity of sucrase in duodenum(P<0.05); the supplementation of 0.46% ZnCP significantly increased egg weight at 4 wk (P<0.05); ZnCP supplementation did not affect eggshell strength, eggshell thickness, yolk color, Haugh unit or the activity of amylase, lipase, trypsin in pancreas and duodenum (P>0.05).The second trial was conducted to study the effects of ZnCP on metal contents in various tissues and activities of zinc-containing enzymes in liver of laying hens. The materials and methods used were the same as that in trial 1. The results showed that compared with control group, the supplementation of 0.34% ZnCP significantly increased the contents of Zn and Fe in blood and liver (P<0.05); the supplementation of 0.46% ZnCP significantly increased the content of Zn in liver, the content of Fe in blood and the content of Zn or Ca in pancreas (P<0.05); the supplementation of 0.23% ZnCP significantly improved he content of Fe in blood and the activity of LDH in liver (P<0.05); the supplementation of 0.46% ZnCP significantly increased the content of Zn in shinbone and yolk, the content of Zn or Ca in pancreas and the activity of AKP in liver compared with 0.11% ZnCP(P<0.05).The third trial was conducted to study the effects of ZnCP on the expression of zinc transporter gene in pancreas and jejunum of laying hens. The materials and methods used were the same as that in trial 1. The results showed that compared with control group, the supplementation of 0.23% ZnCP significantly increased the mRNA levels of ZnT2 in jejunum(P<0.05); the supplementation of 0.34% ZnCP significantly increased the mRNA levels of ZnT1、ZnT2、ZnT5 and MT-4 in pancreas(P<0.05); the supplementation of 0.46% ZnCP significantly increased the mRNA levels of MT-4 in pancreas and ZnTl in jejunum(P<0.05); ZnCP supplementation did not affect the expression of of MTF-1 and MT-3 gene in pancreas or MTF-1 gene in jejunum(P>0.05).