| This study includes two experiments; the first one was to analyze content of copper, iron, zinc, and manganese in those feedstuffs with widely used in practical laying production. The second experiment was to investigate the effects of trace mineral supplemental levels on the production performance, plasma, egg quality and trace mineral contents of excretion in laying hens.In Exp.1, one hundred and seventeen samples of eleven feedstuffs (including corn, wheat, wheat bran, rice bran, distiller's dried grain soluble, corn gluten meal, fish meal, soybean meal, rapeseed meal, cotton seed meal, limestone, and dicalicium phosphate) covers seven geographical regions in China was collected to examine the Cu, Fe, Zn, and Mn concentrations by atomic absorption spectrophotometry following wet digestion, then estimate the variation of trace mineral concentrations. Results showed that for the Fe, Zn, and Mn concentrations, limestone and phosphate were much higher than those contained protein feed sources (soybean meal, rape seed meal and so on), and energy feed sources contained the least by comparison. However, for the copper concentration, protein feedstuffs is the richest followed by limestone or phosphate, and energy sources contained the least. There is a large variation of trace mineral concentration even in the same feedstuff, for example the CV of Zn and Mn in limestone is 161.93% and 62.17%, respectively. The CV of Cu and Fe in rapeseed meal is 48.19% and 61.37%, respectively. Zn's CV in the DDGS and fish meal is 50.37% and 62.17%, respectively. Fe's CV in fish meal is 77.25%. when comparing copper, iron, zinc and manganese requirement suggested by NRC and concentrations in feedstuffs,Fe is the most excessive and followed by Cu, Zn and Mn. Limestone and phosphate contribute as much as 50.49% and 66.47% of the requirement of Fe and Mn,respectively, the majority of Cu and Zn came from energy and protein sources.In Exp.2, one thousand and five hundred females of an egg-laying strain (20 wk old, Lohmann Brown) were used by the quadratic general rotary unitized design (four factors, half done). Copper, iron, zinc and manganese were all supplied in the form of sulfate, and the experiment will be conducted till 35 week of age. The results showed that the 12 treatment has the badly rate and amount of egg production (P<0.05), the 9 treatment has the highest rate of broken eggs (P<0.05), feed:egg obtained improved in the 12 treatment, trace mineral supplementation did not affect the feed intake for laying hens. The results indicated that there was significant positive relation beween the feed:egg and the supplemental levels of manganese(y=0.001x+2.519, P<0.01)but significant negtive relation beween the rate of broken eggs and supplemental levels of copper(Y=-0.027x+1.546, P<0.01).The 12 treatment's RBC and Hct is the lowest in all treatment(P<0.05), AKP and Cu-Zn SOD did not response with the various supplementations of the four minerals, the content of cholesterol,Fe, Mn did not response with different levels of the four minerals in the egg yolks, the content of Zn and Cu in egg yolk differed significantly. The contents of trace minerals in excreta were higher than thoes in diets, but there was no significant correlation beween them.Based on results of the present research, The contents of trace minerals in feedstuff were in various changes, and the iron varied the most and followed by zinc and manganese, however, copper showed a relatively consistent concentrations. There is a large variation of trace mineral concentration even in the same feedstuff. So trace mineral supplementation should be considered based on the basal concentrations. There was complicated interaction among trace minerals and no significant correlation between the contents of trace minerals in feedstuff and thoes in eggs and excreta. In the laying period, the level of copper, iron, zinc and manganese affected production and plasma indicator of laying hens. On the base of practical diets, the recommended supplemental levels of trace minerals were Cu 33.64, Fe 100.92, Zn 67.28, Mn 50.46 mg/kg。...
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