| Calcium(Ca)is one of the key nutrients in the laying cycle,and zinc(Zn)is one of the essential trace elements included in metabolic processes in laying hens.Ca and Zn play important roles in the bone health and eggshell quality through various metabolism and physiological processes.In this study,laying hens were used as models to investigate the effects of daily dynamic Ca and Zn feeding regime(different levels of Ca or Zn were fed in the morning and afternoon respectively,but the total Ca or Zn level was not changed each day)on laying performance and egg quality.Meanwhile,the effects on the diurnal variation of Ca,Phosphorus(P)and Zn in serum and tibia of laying hens were investgated,thus providing a new method for precise nutrition of laying hens.1.A study on the effects of daily dynamic Ca feeding regime on the diurnal variation of Ca,P and Zn in laying hens and its regulationA total of 180 Brown Hy-line,41 weeks old of laying hens were divided into 3treatments randomly with 6 replicates in each treatment and 10 birds in each replicate.During 10 weeks experiment period,control group(CON group)received control diet(contained 3.4% Ca)at both 0730 h and 1530 h respectively,low-high group(LH group)received low Ca diet(contained 3.2% Ca)at 0730 h and high Ca diet(contained 3.6% Ca)at 1530 h respectively,while High-Low group(HL group)received high Ca diet at 0730 h and low Ca diet at 1530 h respectively.The daily feed intake,daily egg production(EP)and other relevant data were recorded.With initial starting at 0000 h before feeding in a daily cycle after 10 weeks of trial period,one chicken was killed at 8 h intervals,and blood,left tibia,jejunum and kidney samples were collected for subsequent analysis.At the same time,four eggs were randomly collected from each replicate to to subsequent analysis.The results indicated that:(1)Compared with LH group,the feed conversion ratio(FCR)of HL group was significantly decreased(P<0.05).Compared with the CON group,the Ca intake of HL group was the highest in the morning(P<0.05).At 0000 h,daily dynamic Ca feeding regime up regulated significantly the m RNA expression level of carbonic anhydrase(CA)in kidney of LH group(P<0.05).In addition,at 1600,the m RNA expression levels of CA in kidney of HL group,SOD and GPX1 in kidney of LH group were significantly down regulated(P<0.05).(2)In CON group,compared with 0800 h,the serum and tibia Zn level of hens decreased significantly at 1600 h(P<0.05).In LH group,compared with 0000 h,serum P level of hens significantly decreased at 1600 h(P<0.05).Compared with CON group,at 0000 h,daily dynamic Ca feeding regime decreased significantly serum Ca level and Ca:P ratio in LH group,Ca level and Ca:Zn ratio in HL group,but increased significantly Ca:Zn ratio in tibia of HL group(P<0.05).At 0800 h,the Ca:P ratio in serum of LH group was significantly decreased(P<0.05).In addition,at 1600 h,daily dynamic Ca feeding regime reduced significantly the serum Ca and Zn levels of LH group,the tibia Ca:P ratio of HL group and the tibia Ca:Zn ratio of LH group(P<0.05).(3)Compared with CON group,at 0000 h,daily dynamic Ca feeding regime increased significantly the m RNA expression levels of PMCA and Ca BP in kidney of LH group(P<0.05),whereas decreased significantly that of PMCA in kidney of HL group.And it decreased significantly that of PMCA and Ca BP in kidney of LH group at 0800 h and 1600 h(P<0.05).In addition,the m RNA expression levels of CLOCK and BMAL1 in jejunum of HL group significantly decreased at 0000 h and 1600 h,as well as CLOCK in kidney at 0000 h(P<0.05).2.A study on the effects of daily dynamic Zn feeding regime on the diurnal variation of Ca,P and Zn in laying hens and its regulationA total of 162 Hy-line,21 weeks old of laying hens were divided into 3treatments randomly with 6 replicates in each treatment and 9 birds in each replicate.During 10 weeks experiment period,control group(CON group)received normal Zn control diet(supplemented with 60 mg of Zn)at both 0530 h and 1530 h respectively,low-high group(LH group)received low Zn diet(basal diet without Zn supplementation)at 0530 h and high Zn diet(supplemented with 120 mg of Zn)at1530 h respectively,while High-Low group(HL group)received high Zn diet at 0530 h and low Zn diet at 1530 h respectively.The daily feed intake,daily egg production(EP)and other relevant data were recorded.With initial starting at 0000 h before feeding in a daily cycle after 10 weeks of trial period,one chicken was killed at 8 h intervals,and blood,left tibia,duodenum and eggshell gland samples were collected for subsequent analysis.At the same time,four eggs were randomly collected from each replicate to subsequent analysis.The results indicated that:(1)Compared with CON group,FCR of LH and HL group were significantly decreased(P<0.05).The Zn intake of LH and HL group was the significant difference in the morning and the afternoon(P<0.05).At 0000 h,daily dynamic Zn feeding regime increased significantly the serum T-AOC value and Cu Zn-SOD activity of LH and HL group(P<0.05),as well as the serum CA activity of HL group and serum ALP activity of LH group at 1600 h(P<0.05).However,the serum MDA value of HL group at 0800 h and the serum ALP activity of LH group at 1600 h reduced significantly(P<0.05).In addition,it up regulated significantly the m RNA expression level of CA in duodenum of LH group at 0000 h,as well as ALP in duodenum,ALP and SOD in eggshell gland of HL group at 1600 h(P<0.05).In addition,the m RNA expression levels of CA in eggshell gland of LH group at 0000 h and 0800 h,CA in eggshell gland of HL group at 0800 h were significantly down regulated(P < 0.05).(2)In CON group,compared with 0000 h,the serum Zn level of hens decreased significantly at 1600 h(P<0.05).In LH group,compared with 0800 h,serum Ca level of hens significantly increased at 0000 h and 1600 h,as well as serum P level at 0000h(P<0.05),and compared with 0000 h,tibia P level of hens significantly decreased at0800 h and 1600 h,as well as tibia Zn level at 0000 h and 1600 h compared to 0800 h(P<0.05).Compared with CON group,daily dynamic Zn feeding regime decreased significantly yolk Ca level,Ca:P and Ca:Zn ratio in LH and HL group(P<0.05).At0000 h,serum P level increased significantly whereas Ca:P ratio decreased significantly in HL group(P<0.05).At 0800 h,in LH group,serum Ca level decreased significantly,but tibia Ca and Zn level increased significantly(P<0.05),but increased significantly Ca:Zn ratio in tibia of HL group(P<0.05).At 1600 h,the serum Zn levels of HL group increased significantly,but Ca:Zn ratio decreased significantly(P<0.05).(3)Compared with CON group,at 0000 h,daily dynamic Zn feeding regime increased significantly the m RNA expression levels of Zn1 in duodenum of LH group(P<0.05),whereas decreased significantly that of NCX1 in duodenum of LH group,Ca BP,Zn1 and Zn5 in eggshell gland of LH and HL group(P<0.05).And it decreased significantly that of Zn5 in duodenum of HL group at 0800 h and Zn5 in eggshell gland of HL group at 1600 h(P<0.05),whereas increased significantly that of Ca BP and NCX1 in eggshell gland of HL group at 1600 h(P<0.05).In addition,at 0000 h,the m RNA expression levels of Per2 in duodenum of HL group increased significantly,as well as Cry1 and Per3 in eggshell gland of HL group at 0800 h,Cry2 in eggshell gland of LH group at 1600 h,CLOCK,Cry2,Per2 and Per3 in duodenum of HL group at 1600 h(P<0.05).However,it decreased significantly BMAL1 in duodenum of HL group at 1600 h(P<0.05).In conclusion,daily dynamic Ca and Zn feeding regime influenced Ca and Zn intake in the morning and afternoon respectively.And compared with LH group,HL group improved FCR.Compared with CON group,both LH and HL groups improved FCR.Daily dynamic Ca and Zn feeding regime affected the antioxidant status of laying hens,the circadian rhythms of Ca,Zn and P metabolism,and the diurnal variation of Ca,P and Zn in the serum and tibia through the regulation of circadian rhythm genes’ expressiong levels.And daily dynamic Ca and Zn feeding regime is of great meaning to improve precise nutrition of laying hens. |
