Effects Of Low Protein Diet On Late Production Performance And Nutritional Regulation Of Laying Hens

This research aims to lay eggs in the late of meiyukou JingBai layers as the research object,to explore the impact of protein levels reduction on the productivity of laying hens,apparent digestibility of nutrients,immunity,antioxidant ability,health effects of liver and intestinal,etc.,under the same energy level as well as three kinds of consistent restrictive amino acids.Moreover,we will continue to explore the effects of this method on the above-mentioned index,by adding compound enzyme preparation and a-Monolaurin with 1%lower protein level,,in order to provide references to develop low protein diet.In this experiment,648 healthy yukou jingbai no.1 laying hens with same weight and laying rate were randomly divided into 6 groups,that is 108 feathers in each group.There were 4 replicates,9 lattices for each repetition and 3 feathers for each lattice.Control group,on the one hand,is with the basis of feeding 16.7%crude protein level,on the other hand,the feeding crude protein level is respectively reduced by 0.5%,1%and 1.5%in the test Ⅰ,Ⅱ and Ⅲ group.The restrictive amino acid lysine,methionine and threonine are add for these three test groups so as to reach the amino acid levels of control group.We additionally added 600mg/kg composite enzyme preparation for test Ⅳ on the basis of test Ⅱ and 400mg/kg α-Monolaurin for test Ⅴon the basis of test Ⅳ.The pre-test period was 7 days,and the formal period was 56 days.Slaughter test was conducted the next day after the end of the test,and samples were collected and tested.The main test results arc as follows:1.Influence on productivity and egg quality of laying hens:Laying rate:there was no significant difference between each group.Feed to egg ratio:dietary protein level decreased,and there was a tendency to increase feed to egg ratio.Adding compound enzyme preparation significantly reduced feed to egg ratio,and the difference was significant(P<0.05).Average egg weight:no significant difference between the groups;Qualified egg rate:addition of compound enzyme alone and addition of the former and α-Monolaurin significantly increased the qualified egg rate(P<0.05).Defective egg rate:addition of compound enzyme preparation alone and addition of the compound enzyme preparation together with α-Monolaurin significantly reduced the defective egg rate,and the effect was better when adding both of them at the same time(P<0.05).Eggshell intensity:compared with test group I,adding compound enzyme preparation together with α-Monolaurin significantly improved the eggshell intensity(P<0.05).Protein height and Haugh unit:the addition of complex enzymes significantly increased the protein height compared with the control group,with a significant difference(P<0.05).Yolk color:the addition of compound enzyme preparation and α-Monolaurin at the same time could improve the yolk color depth compared with the control group(P<0.05).2.Effect on apparent digestibility of various nutrients in laying hens:Digestibility of crude protein:adding compound enzyme preparation alone and adding compound enzyme preparation together with α-Monolaurin significantly improved the digestibility of crude protein.Crude fat digestibility:Addition of compound enzyme preparation alone and addition of compound enzyme preparation together with α-Monolaurin significantly improved the crude fat digestibility.3.Effects on serum biochemical,immunity,antioxidant ability and digestive enzyme activities of duodenal contents in laying hens:Serum biochemical indexes:TP,ALB,GLB,ALB/GLB,ALP,ALT,AST and uric acid were not significantly different among the groups(P>0.05).Immunity index:IL-2:compared with test group Ⅰ and Ⅳ,adding compound enzyme preparation together with α-Monolaurin significantly increased the content of serum IL-2(P<0.05);There was no significant effect on spleen index,IgA,IgG,IgM,IL-4 and TNF-α(P>0.05).Antioxidant indicators:the total antioxidant capacity,adding compound enzyme preparation together with α-Monolaurin increased by 20.6%,25%and 20.6%respectively in control group,test group Ⅰ and test group Ⅱ,with significant difference(P<0.05);MDA:the reduced protein level significantly increased the MDA level in the serum of laying hens,and the addition of compound enzyme preparation alone and the addition of compound enzyme preparation together with α-Monolaurin significantly reduced the MDA level in the serum of laying hens(P>0.05).There was no significant difference for GSH-Px and T-SOD level among groups(P>0.05).Digestive enzyme index:lipase:lipase in duodenal contents was significantly increased by adding the enzyme preparation alone and by adding the former together with α-Monolaurin(P<0.05).Trypsin:adding the enzyme preparation alone and adding the former together with α-Monolaurin significantly increased the activity of trypsin in duodenal contents(P<0.05).Amylase:adding the enzyme preparation alone and adding the former together withα-Monolaurin significantly increased the activity of amylase in duodenal contents(P<0.05).4.Effects on liver and intestinal health of laying hens:Viscera index:the liver index:compared with test group Ⅱ,adding compound enzyme preparation alone and adding the former together with α-Monolaurin reduced the liver index significantly(P<0.05);Intestinal structure index:duodenal recess depth:adding the compound enzyme preparation alone and adding the compound enzyme preparation together with α-Monolaurin significantly reduced the depth of duodenal recess,and the addition of both of them at the same time reduced the depth of duodenal recess even more(P<0.05).Height of jejunum villi:decreased protein level significantly reduced the height of j ejunum villi in laying hens,with significant difference(P<0.05).Jejunum leukoenetic ratio:the reduction of protein significantly increased jejunum leukoenetic ratio,and the addition of compound enzyme preparation alone as well as addition of compound enzyme preparation together with α-Monolaurin significantly increased jejunum leukoenetic ratio(P<0.05).Intestinal flora index:there was no significant difference in the diversity of flora in each group.The decrease of dietary protein had a significant effect on the intestinal structure of laying hens,which reduced the relative abundance of bacteria and improved the intestinal health of laying hens.adding compound enzyme preparation changed the intestinal flora structure of laying chicken cecum and adding compound enzyme preparation with α-Monolaurin at the same time improved the intestinal flora structure of laying chicken cecum.To sum up,the decreased dietary protein level of laying hens had no significant effect on productivity and egg quality.The decrease of protein level reduced antioxidant capacity,improved intestinal structure.It had no significant effect on the diversity of intestinal flora but improved the structure of intestinal flora.The productivity and egg quality of laying hens were improved by adding compound enzyme preparation alone.The apparent digestibility of crude protein and crude fat was also increased.Antioxidant ability was improved.It improved the activity of digestive enzymes,promoted the structure of intestinal flora,and changed the structure of intestinal flora.The addition of compound enzyme preparation and α-Monolaurin at the same time increased the qualified egg rate,enhanced the strength of the egg shell,and deepened the color of the yolk.The immune performance and antioxidant capacity of layer were improved as well.It promoted the activity of digestive enzymes,decreased the liver index and improved the intestinal health.