Effects Of Diet Supplemented With Different Zinc Levels On Production Performance, Biochemical Parameters And Expression Of Metallothionein In Laying Hen

The study was carried out to determine the effects of diet supplemented with different zinc levels on production performance, egg quality, biochemical parameters, reproductive hormone and expression of hepatic and renal metallothionein in laying hen, while discuss the suitable zinc supplement in diet and evaluated index of zinc nutritional status in laying hen.Effects of diet supplemented with different zinc levels on production performance and biochemical parameters in laying henSixty-six 18-week old ISA puberty hens were randomly selected and divided into control, treatment 1 and treatment 2 groups with the basal diet supplemented with different zinc levels at the dosage of 0, 60, 180mg/kg, respectively. The production performance and quality of egg were observed; zinc contents in serum and various tissues were determined by ICP;E2 and P concentrations in serum were analyzed by RIA; activity of serum AKP was investigated by DGKC suggested impetus method. The results showed that egg production,feed conversion ratio and feed consumption were not affected by supplemental zinc at the period of 21~28 weeks old; In compared with control group, percentage of eggs with defective shells was decreased at treatment groups, but no significant difference(P＞0.05); Shell thickness of egg was obviously decreased(P＜0.05), while there were no significant difference in egg shape index, strengthen of shells, Haugh unit and the weight of albumen, yolk and shell(P＞0.05). At the period of 29~36 weeks old, there were no obvious difference in egg production, feed conversion ratio and feed consumption and egg quality; But egg weight and percentage of egg with defective shell were observed to descend significantly in treatment groups. Slaughter experiment at 28-week old showed that zinc content in liver, tibia and egg were significantly promoted at treatment groups(P＜0.05),while there were the trend to be increased in feather and serum. AKP activity and E2 concentration in serum were higher at treatment 1 group than that at control group(P＜0.05), and no difference with treatment 2 group(P＞0.05); while P concentration in serum was no obviously difference at all groups(P＞0.05).Effects of diet supplemented with different zinc levels on expression of hepatic and renal metallothioneion in laying henThe other partial experiment was conducted to determine hepatic and renal MT mRNAs expression in laying hen when supplemented with three different zinc levels. Five laying hens was randomly selected to slaughter and collect the samples of liver and kidney .The hepatic and renal MT mRNA content were measured by RT-PCR. The results showed that the expression of hepatic MT mRNA at treatment 1 group was higher then that at the other groups(P＜0.05),and there were no significant difference between control and treatment 2 groups(P＞0.05).MT mRNA was more abundant at treatment 1 group than that at treatment 2 group in kidney(P＜0.05), while there was no significant difference between treatment 1 and control group(P＞0.05), and the difference between control and treatment 2 was not significant(P＞0.05). The results suggest that the different zinc levels in diet affect expression of hepatic and renal MT mRNA in laying hen. In conclusion, the basal diet supplemented with zinc at the dose of 60 mg/kg was the best in this experiment. And zinc content in serum and tissues, activity of serum AKP and hepatic MT mRNA can evaluate the zinc nutritional status in laying hen.