Adjusting phosphate feeding regimen according to daily rhythm increases eggshell quality via enhancing medullary bone remodeling in laying hens

Background Body phosphorus metabolism exhibits a circadian rhythm over the 24-h daily cycle.The egg laying behavior makes laying hens a very special model for investigating phosphorus circadian rhythms.There is lack of information about the impact of adjusting phosphate feeding regimen according to daily rhythm on the phosphorus homeostasis and bone remodeling of laying hens.Methods and results Two experiments were conducted.In Exp.1,Hy-Line Brown laying hens(n=45)were sampled according the oviposition cycle(at 0,6,12,and 18 h post-oviposition,and at the next oviposition,respectively;n=9 at each time point).Diurnal rhythms of body calcium/phosphorus ingestions and excretions,serum calcium/phosphorus levels,oviduct uterus calcium transporter expressions,and medullary bone(MB)remodeling were illustrated.In Exp.2,two diets with different phosphorus levels(0.32%and 0.14%non-phytate phosphorus(NPP),respectively)were alternately presented to the laying hens.Briefly,four phosphorus feeding regimens in total(each included 6 replicates of 5 hens):(1)fed 0.32%NPP at both 09:00 and 17:00;(2)fed 0.32%NPP at 09:00 and 0.14%NPP at 17:00;(3)fed 0.14%NPP at 09:00 and 0.32%NPP at 17:00;(4)fed 0.14%NPP at both 09:00 and 17:00.As a result,the regimen fed 0.14%NPP at 09:00 and 0.32%NPP at 17:00,which was designed to strengthen intrinsic phosphate circadian rhythms according to the findings in Exp.1,enhanced(P<0.05)MB remodeling(indicated by histological images,serum markers and bone mineralization gene expressions),elevated(P<0.05)oviduct uterus calcium transportation(indicated by transient receptor potential vanilloid 6 protein expression),and subsequently increased(P<0.05)eggshell thickness,eggshell strength,egg specific gravity and eggshell index in laying hens.Conclusions These results underscore the importance of manipulating the sequence of daily phosphorus ingestion,instead of simply controlling dietary phosphate concentrations,in modifying the bone remodeling process.Body phosphorus rhythms will need to be maintained during the daily eggshell calcification cycle.

POD analysis of the instability mode of a low-speed streak in a laminar boundary layer

The instability of one single low-speed streak in a zero-pressure-gradient laminar boundary layer is investigated experimentally via both hydrogen bubble visualization and planar particle image velocimetry(PIV) measurement. A single low-speed streak is generated and destabilized by the wake of an interference wire positioned normal to the wall and in the upstream. The downstream development of the streak includes secondary instability and self-reproduction process, which leads to the generation of two additional streaks appearing on either side of the primary one. A proper orthogonal decomposition(POD) analysis of PIV measured velocity field is used to identify the components of the streak instability in the POD mode space: for a sinuous/varicose type of POD mode, its basis functions present anti-symmetric/symmetric distributions about the streak centerline in the streamwise component, and the symmetry condition reverses in the spanwise component. It is further shown that sinuous mode dominates the turbulent kinematic energy(TKE) through the whole streak evolution process, the TKE content first increases along the streamwise direction to a saturation value and then decays slowly. In contrast, varicose mode exhibits a sustained growth of the TKE content,suggesting an increasing competition of varicose instability against sinuous instability.

Dynamics of low-speed streak evolution and interaction in laminar boundary layer

The present paper presents an experimental effort on the regeneration process of two low-speed laminar streaks in a zero-pressure-gradient laminar boundary layer. Two vertical thin wires separated by a spanwise distance of 30 mm are used to introduce disturbances of two rolls of transitional Karmain vortex street to the downstream boundary layer. Both hydrogen bubble visualization and particle image velocimetry （PIV） measurement show that two lowspeed streaks are induced through leading-edge receptivity process. As these streaks develop in the downstream, two additional low-speed streaks begin to appear outboard of the flank of the original two, together with complex dynamics of streak splitting and merging. A flow pattern of four streaks aligned along the spanwise direction occurs finally in the far downstream. It is found that besides the mechanisms of streak breakdown, the streak interaction is also an important factor characterizing the instability of low speed streaks and their regeneration process.

Effect of drag reducing riblet surface on coherent structure in turbulent boundary layer

The characteristics of turbulent boundary layer over streamwise aligned drag reducing riblet surface under zero-pressure gradient are investigated using particle image velocimetry. The formation and distribution of large-scale coherent structures and their effect on momentum partition are analyzed using two-point correlation and probability density function. Compared with smooth surface, the streamwise riblets reduce the friction velocity and Reynolds stress in the turbulent boundary layer, indicating the drag reduction effect. Strong correlation has been found between the occurrence of hairpin vortices and the momentum distribution. The number and streamwise length scale of hairpin vortices decrease over streamwise riblet surface. The correlation between number of uniform momentum zones and Reynolds number remains the same as smooth surface.

A simple daily dynamic feeding regimen for reducing phosphorus consumption and excretion in laying hens

Phosphorus metabolism in laying hens is a highly dynamic process over the course of the 24 h egg-laying cycle.Adjusting the phosphorus feeding regimen according to the daily egg-laying cycle may help to improve phosphorus utilization efficiency.Hy-Line Brown layers(n=120;70 wk old)were offered 4different phosphorus daily regimens:(1)RR,fed regular phosphorus at both 09:00 and 17:00;(2)RL,fed regular phosphorus at 09:00 and low phosphorus at 17:00;(3)LR,fed low phosphorus at 09:00 and regular phosphorus at 17:00;(4)LL,fed low phosphorus at both 09:00 and 17:00.The regular and low phosphorus diets contained 0.32% and 0.14% non-phytate phosphorus,respectively.The feeding trial lasted for 12 wk.As a result,layers on the RL regimen had decreased laying rate(P<0.05;5 to 8,9 to 12,and 1 to 12 wk)when compared to all other regimens.Layers on the LL regimen had decreased eggshell thickness and specific gravity(P<0.05;wk 8)when compared to all other regimens,and had decreased egg shell strength(P<0.05;wk 8)when compared to RL and LR regimens.When compared to the RR regimen(a common practice in the industry),layers on the LR regimen had:(1)identical laying performance and egg quality(P>0.05);(2)decreased phosphorus excretion(P<0.05)during the period of09:00 to 17:00;(3)increased jejunal calbindin D28k protein expression(P<0.05)2 h after feeding in the morning;(4)decreased serum fibroblast growth factor 23 and calcitriol levels(P<0.05),decreased jejunal type Ⅲ sodium-phosphate cotransporter 2 gene and protein expression(P<0.05),and decreased renal type Ⅲ sodium-phosphate cotransporter 1 protein expression(P<0.05),2 h after feeding in the afternoon.In summary,when dietary phosphorus was supplemented in accordance with daily serum phosphorus rhythms(i.e.,the LR regimen),laying performance and egg quality were well supported whilst significantly decreasing phosphorus consumption and excretion.Thus,serum phosphorus rhythms will need to be carefully maintained when developing dietary phosphorus-reduction strategies in laying hens.

Dietary vitamin D_(3) deprivation suppresses fibroblast growth factor 23 signals by reducing serum phosphorus levels in laying hens

The present study was carried out to evaluate the effect of dietary supplemental vitamin D_(3) on fibroblast growth factor 23(FGF23)signals as well as phosphorus homeostasis and metabolism in laying hens.Fourteen 40-week-old Hy-Line Brown layers were randomly assigned into 2 treatments:1)vitamin D_(3) restriction group(n=7)fed 0 IU/kg vitamin D_(3) diet,and 2)regular vitamin D_(3) group(n=7)fed 1,600 IU/kg vitamin D_(3) diet.The study lasted for 21 d.Serum parameters,phosphorus and calcium excretion status,and tissue expressions of type II sodium-phosphate co-transporters(NPt2),FGF23 signals and vitamin D_(3) metabolic regulators were determined.Hens fed the vitamin D_(3) restricted diet had decreased serum phosphorus levels(by 31.3%,P=0.028)when compared to those fed regular vitamin D_(3) diet.In response to the decreased serum phosphorus,the vitamin D_(3) restricted laying hens exhibited:1)suppressed kidney expressions of 25-hydroxyvitamin D 1-a-hydroxylase(CYP27B1,by 52.8%,P=0.036)and 1,25-dihydroxyvitamin D 24-hydroxylase(CYP24A1,by 99.4%,P=0.032);2)suppressed serum levels of FGF23(by 14.6%,P=0.048)and increased serum alkaline phosphatase level(by 414.1%,P=0.012);3)decreased calvaria mRNA expressions of fibroblast growth factor receptors(FGFR1,by 85.2%,P=0.003,FGFR2,by 89.4%,P=0.014,FGFR3,by 88.8%,P=0.017,FGFR4,by 89.6%,P=0.030);4)decreased kidney mRNA expressions of FGFR1(by 65.5%,P=0.021),FGFR4(by 66.0%,P=0.050)and KLOTHO(by 68.8%,P=0.038);5)decreased kidney protein expression of type 2a sodium-phosphorus co-transporters(by 54.3%,P=0.039);and 6)increased percent excreta calcium(by 26.9%,P=0.002).In conclusion,the deprivation of dietary vitamin D_(3) decreased FGF23 signals in laying hens by reducing serum FGF23 level and suppressing calvaria and kidney mRNA expressions of FGF23 receptors.