| In the experiment,using the slope-ratio technique , the experiment was conducted with 900 one-day old broilers to estimate bioavailability of zinc-amino acid chelate (Zn-AA). 2X5 factorial design was used in the experiment.Broilers were allotted randomly to 9 dietary treatments with 5 duplicates that included a basic diet (control group) and 8 tested diets which were formed by supplemental with different levels (20,50,100 and l50mg/kg) of inorganic Zinc and Zn-AA respectively. The trail tasted 7 weeks and the chicks were allowed ad libitum access to feed and water. ADG , ADFI and F/G were recorded during 0-3 weeks and 4-7 weeks.At 3rd and 7th weeks,one broiler was chosen randomly from each replicate,and blood samples were pooled by replicate.Serum was then prepared by centrifugation.Lymphocyte number and lymphocyte proliferative response were measured.Chicks were killed and thymus,spleen and bursa of Fabricius were removed to weight to calculate the ration of organ weight to body weight.At the same time.samples of muscle.liver and skin were collected to measure Zinc concentration.The results indicated that: (1) Supplementation with inorganic Zinc and Zn-AA had the tendence to improve the growth performance of 0-7-week old broiler.Compared to the control group,ADG were increased by 5.93-13.07% and 10.66-13.84% respectively,ADFI were increased by 5.02-12.74% and 10.44-12.81%.At 0-3 week period, compared to the control group,ADFl were decreased by 3.72%,5.12%, 1.24%,0.88% and 1.71%,2.06%.1.24%,0.72% respectively for inorganic Zinc and Zn-AA treatment (P>0.05) .(2) Under the condition of this experiment,compared to the control group,with the increasing dietary Zn level.Zn content in determined tissues and organs.serum Zn increased .(3) Under the condition of this experiment,with the increasing dietary Zn level.Ea.Et and lymphocyteproliferative Response of the broilers increased signincantly(p<0.05 or p<0.01),but immunity organs' exponent wasn't affected by the Zn supplementation (P>0.05) (4) Under the condition of the experiment, using means of ADG and ADFI as evaluated index,at 0-3 week-stage.the optima supplemental levels of Zn-AA were 64.5 mg/kg, 103 mg/kg and those of inorganic Zn were 111.11mg/kg .65.83 mg/kg respectively. At 4-7 week-stage.the optima supplement of Zn-AA were 107.94 mg/kg,100.43 mg/kg and the optima supplement inorganic Zn 175mg/kg ,192.63 mg/kg respectively. At 0-7 week-stage.the optima supplement of Zn-AA were 93.43 mg/kg,92.64 mg/kg and the optima supplement inorganic Zn 123.5mg/kg ,129.75 mg/kg respectively.?In the experiment.using the slope-ratio technique ,ADG and Zn content of serum and liver were sensitive indicator.lf Zn from ZnSO4 7H2O set at 100%,the relative bioavailability were estimated to be 101.72%, 144.67% and 125.97% during 0-3 week-period and 151.82%. 192.42% and 106.82% during 0-3 week-period.The experiment showed that the performance of the broilers was improved with zinc supplementation,the bioavailability of zinc aniino acid chelate estimated by ADG, zinc contents in serum and liver was higher than that of inorganic zinc .Zinc supplementation can improve immunity function.
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