| Mineral elements are important substances that constitute the body's tissues,and are the components of enzymes in most metabolic pathways of the human body.Mineral element additives have four types:inorganic salt type,organic acid type,chelating type and bio-fermentation type.Among them,inorganic salt type is widely used because of its low cost.The advantages of chelating type and bio-fermentation type mineral element additives are obvious,and they are gradually applied in the production of laying hens.This study was based on the determination of the appropriate amount of phytase,reducing or even eliminating the influence of phytase on the digestion and absorption of mineral elements.The purpose of the study was carried out to determine effects of different levels of trace elements on the performance,egg quality and mineral element emissions of laying hens in order to provide reference for the rational use of inorganic salt and bio-fermentation mineral element additives and to reduce feeding costsExperiment 1:Thirty 5 5-week-old age New Yangzhou chicken cocks were selected and randomly divided into five groups with six replicates.The first group was fed a phytase-free diet as a control group;B,C,D,and E were the experimental groups and 150 U/kg,300 U/kg,450 U/kg,and 600 U/kg phytase were added to the basal diet,respectively.The results showed that:(1)Compared with the control group,the chickens in group C and D had an extremely significant improvement on the apparent utilization of dry matter(P<0.01),and the chickens in group C,D and E had significant improvement on the utilization of crude protein(P<0.01),the experimental group chickens had different degrees of improvement on the apparent utilization of coarse ash(P<0.05,P<0.01).(2)Compared with control group,the apparent utilization rate of calcium and phosphorus in each experimental group were significantly increased(P<0.05,P<0.01).(3)There was no significant difference in the apparent utilization rate of copper among the experimental groups(P>0.05),but the apparent utilization rate of manganese and zinc increased significantly(P<0.01).To sum up,adding phytase in diet can improve the apparent utilization of crude protein,calcium,phosphorus,copper,manganese and zinc in laying hens,and the appropriate amount of phytase is 300 U/kgExperiment 2:A total of ong thousand one hundred and fifty two 43-week-old Hy-line brown layers were randomly divided into 6 groups with 6 replicates in each group and 32 in each replicate.Group 1 was added with inorganic trace elements and the contents of copper,iron,zinc and manganese were 8 mg/kg,80 mg/kg,70 mg/kg and 80 mg/kg,respectively.Group 2 and Group 3 were supplemented with different proportions of organic and inorganic trace elements.The amount of organic copper,iron,zinc and manganese in group 2 was 1 mg/kg,10 mg/kg,5 mg/kg,10 mg/kg respectively,and that of inorganic copper,iron,zinc and manganese was 6 mg/kg,50 mg/kg,50 mg/kg,50 mg/kg respectively.The amount of organic copper,iron,zinc and manganese in group 3 was 2 mg/kg,20 mg/kg,15 mg/kg,20 mg/kg respectively,and that of inorganic copper,iron,zinc and manganese was 4 mg/kg,30 mg/kg,30 mg/kg,30 mg/kg respectively.Group 4 and group 5 were added with organic trace elements and the amount of copper,iron,zinc and manganese in group 4 was 5 mg/kg,45 mg/kg,40 mg/kg and 40 mg/kg respectively,and that in group 5 was 6 mg/kg,60 mg/kg,25 mg/kg and 40 mg/kg respectively.The experimental period was 8 weeks.The test results show that:(1)Production performance:Dietary supplementation of different types and levels of trace elements had a significant impact on laying rate and egg weight(P<0.05).Group 3 had the highest laying rate and the lowest mortality rate,but there was no significant difference in the mortality rate of laying hens among the groups(P>0.05)(2)Egg quality:Dietary supplementation of different types and levels of trace elements had significant effects on albumen height,yolk color and Haugh units(P<0.05).Group 1 had the highest albumen height and Haugh units,but had the lightest yolk color.Group 3 had no significant differences in eggshell breaking strength,albumen height and Haugh unit between groups(P>0.05),but the yolk color was significantly larger than that of Group 1(P<0.05).(3)Deposition and emission of mineral elements:From the analysis of the contents of trace elements in egg white,yolk and feces,the addition of different types and levels of trace elements in diet had a significant effect on the content of calcium,iron,manganese and zinc in egg white and egg yolk(P<0.05)and on the content of manganese and copper in chicken feces(P<0.05).In general,group 1 promoted the deposition of mineral elements in egg white and group 5 promoted the deposition of mineral elements in egg yolk.Each group had different effects on the content of mineral elements in chicken fecesThe optimum amount of phytase added to diets of laying hens is 300 U/kg.The mixed addition of organic and inorganic microelements can achieve better results,and reduce the cost of diets. |
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