Influence of Age and Phylogenetic Background on Blood Parameters Associated With Bone Metabolism in Laying Hens

Effect of laying parity and sex ratio on reproduction performance and biochemical parameters of White Roman geese kept in an environmentally controlled house

1. This study aimed to investigate the effect of the first and third parities and one male: four females (1 M:4F) and 1 M:6F sex ratios of White Roman geese on their reproductive performance and biochemical parameters in an environmentally controlled house.2. Ganders (n = 136) and geese (n = 656) from the first and third parity were randomly placed into eight pens. These eight pens were assigned to one of four treatments in a 2 × 2 factorial arrangement (two sex ratio groups × two parity groups). The first and third parity treatment groups had 1 M:4F (each pen containing 20 ganders and 80 geese) and 1 M:6F (each pen containing 14 ganders and 84 geese) sex ratio treatment groups, respectively, replicated twice.3. Blood samples were collected from the geese at different time points: upon entering the house (ST), the beginning of the lighting regime of 7 L:17D for six weeks (LC6W), lighting adjustment to 9 L:15D for 6 weeks (9C6W), the peak of egg production (PEP) and the end of egg production (EEP).4. The first parity group had a longer laying period than the third parity (274 vs.191 days). First parity had a lower egg production rate than third parity during whole stage (18.7 vs. 25.4%). Fertility in 1 M:4F group was significantly higher than in 1 M:6F rate group (54.7 vs. 45.1%) at all periods.5. Plasma levels of total protein, albumin, globulin, triglycerides, calcium and phosphorus concentrations were significantly higher for whole laying period in first parity geese compared to third parity birds.

Effects of a transient lack of dietary mineral phosphorus on renal gene expression and plasma metabolites in two high-yielding laying hen strains

BACKGROUND

There is an emerging body of evidence that current poultry feed is formulated in excess for phosphorus (P), which results in unnecessarily high P excretions. Sustainable concepts for agricultural P flows should trigger animal-intrinsic mechanisms for efficient P utilization. In the current study, Lohmann Brown (LB) and Lohmann Selected Leghorn (LSL) laying hens were fed either a high P diet (P+) with 1 g/kg mineral P supplement or a low P diet (P-) with 0 g/kg mineral P supplement for a period of 4 weeks prior to sampling. Before and after onset of laying, i.e., at 19 and 24 weeks of life, kidney and plasma samples were collected to investigate the endogenous P utilization in response to restricted dietary P, laying hen strain, and sexual maturation.

RESULTS

Plasma analyses of minerals and metabolites confirmed the response to a low P diet, which was characterized by a significant reduction in plasma P levels at week 19 in both strains. The plasma calcium (Ca) levels were tightly regulated throughout the entire experimental period. Notably, there was a numerical trend of increased plasma calcitriol levels in P- fed birds of both strains compared to the P + group, which might have mediated a substantial role regarding the adaptive responses to low P supply. At week 19, RNA sequencing of kidney identified 1,114 and 556 differentially expressed genes (DEGs) unique to the LB and LSL strains, respectively. The number of DEGs declined with increasing maturity of the hens culminating in 90 and 146 DEGs for LB and LSL strains at week 24. Analyses revealed an enrichment of pathways related to energy metabolism and cell cycle, particularly at week 19 in both strains. The diet-specific expression of target genes involved in P homeostasis highlighted transcripts related to active (SLC34A1, SLC20A2) and passive mineral transport (CLDN14, CLDN16), Ca utilization (STC1, CALB1), and acid-base balance (CA2, SLC4A1).

CONCLUSIONS

Results suggest that both laying hen strains adapted to the lack of mineral P supplements and achieved a physiological Ca: P-ratio in body compartments through endogenous regulation as evidenced via the endocrine profile.

Influence of perch provision during rearing on activity and musculoskeletal health of pullets

Prior research suggests exercise during pullet rearing can mitigate lay-phase bone fractures by strengthening muscles, enhancing balance, and increasing bone mass. This study aimed to confirm that Hy-Line brown pullets with multi-tier perches show increased activity and improved musculoskeletal health. Pullets (n = 810) were randomly allocated to housing systems, either with multi-tier perches (P; n = 15 pens) or without (NP; n = 15 pens), spanning from 0-17 weeks of age. At 5, 11, and 17 weeks, individual birds were meticulously monitored for activity using accelerometers over three consecutive days (n = 90 randomly selected birds/week). At 11 and 17 weeks, 60 birds underwent euthanasia and computed tomography (CT) scans to ascertain tibiotarsal bone mineral density and cross-sectional area measurements. Post-CT scanning, birds were dissected for muscle size, tibiotarsal breaking strength, and tibiotarsal ash percentage measurements. Additionally, serum concentrations of bone-specific alkaline phosphatase and procollagen type 1 N-terminal propeptide were assessed as markers of bone formation (n = 90 birds/week). Pullet group P exhibited heightened vertical activity (P<0.05), with no discernible differences in overall activity (P>0.05) during weeks 5, 11, and 17 compared to group NP. Tibiotarsal bones of P pullets demonstrated superior total and cortical bone mineral density at week 11, alongside increased cortical bone cross-sectional areas and heightened total and cortical bone mineral densities at week 17 (P<0.05) compared to NP pullets. At week 11, P pullets displayed larger leg muscles, including triceps, pectoralis major and minor, and leg muscles at week 17 (P<0.05) compared to NP pullets. Notably, at both weeks, P pullets' tibiae exhibited greater breaking strengths, higher ash percentages, and elevated concentrations of bone-specific alkaline phosphatase and procollagen type 1 N-terminal propeptide compared to NP pullets (P<0.05). The study findings underscore the benefits of providing multi-tier perches for pullets, serving as a valuable tool for enhancing bird activity and musculoskeletal health preceding the lay phase.

Supplemental effect of Pediococcus acidilactici CNCM I-4622 probiotic on the laying characteristics and calcium and phosphorus metabolism in laying hens

The close link between intestinal microbiota and bone health ('gut-bone' axis) has recently been revealed: the modulation of the amount and nature of bacteria present in the intestinal tract has an impact on bone health and calcium (Ca) metabolism. Probiotics are known to favorably impact the intestinal microbiota. The objective of this study was to investigate the effect of Pediococcus acidilactici CNCM I-4622 (PA) on laying performance, egg/eggshell quality, Ca metabolism and bone mineralization and resistance in relatively old layers (50 wks old at the beginning of the experiment) during 14 weeks. 480 Hy Line brown layers were divided into 2 groups (CON and PA: 3 layers/rep, 80 rep/group) and fed with a diet formulated to be suboptimal in calcium (Ca) and phosphorus (P) (- 10% of the requirements). The total egg weight was improved by 1.1% overall with PA, related to an improvement of the weight of marketable eggs (+ 0.9%). PA induced a decreased % of downgraded eggs, mainly broken eggs (- 0.4 pts) and FCR improvement (- 0.8% for all eggs, - 0.9% for marketable eggs). PA also led to higher Haugh units (HU: + 7.4%). PA tended to decrease crypt depth after the 14 weeks of supplementation period in the jejunum (- 25.2%) and ileum (- 17.6%). As a consequence, the VH/CD ratio appeared increased by PA at the end of the trial in the jejunum (+ 63.0%) and ileum (+ 48.0%). Ca and P retention were increased by 4 pts following PA supplementation, translating into increased bone hardness (+ 19%), bone cohesiveness (+ 43%) and bone Ca & P (+ 1 pt) for PA-supplemented layers. Blood Ca and P were respectively improved by 5% and 12% with PA. In addition, blood calcitriol and osteocalcin concentrations were respectively improved by + 83% and + 3% in PA group at the end of the trial, compared to CON group. There was no difference between the 2 groups for ALP (alkaline phosphatase) and PTH (parathyroid hormone). PA significantly decreased the expression of the following genes: occludin in the small intestine, calbindin 1 in the ovarian tissue and actin B in the bone. PA therefore improved zootechnical performance of these relatively old layers, and egg quality. The parallel increase in Ca and P in the blood and in the bone following PA supplementation suggests an improvement of the mineral supply for eggshell formation without impacting bone integrity, and even increasing bone resistance.

Effects of Perilla Seed Meal on Productive Performance, Egg Quality, Antioxidant Capacity and Hepatic Lipid Metabolism of Wenchang Breeder Hens

The aim of this study was to investigate the effects of adding perilla seed meal (PSM) to the diet on reproductive performance, egg quality, yolk fatty acids, antioxidant capacity and liver lipid metabolism in breeding hens. A total of 192 31-week-old yellow-feathered hens were randomly divided into 4 treatments with 6 replicates of 8 birds for 8 weeks. The chickens were fed a typical corn-soybean meal diet containing 0% (control), 0.3%, 0.6%, and 1% PSM. The results showed that PSM can change the productivity of laying hens. Adding 0.6% PSM to the feed reduced the mortality rate of chickens. Adding 1% PSM improved the fertilization rate and hatching rate of chickens. Regarding egg quality, the albumen height and Haugh unit were improved in the 0.6% PSM group. The content of MUFAs and PUFAs in the egg yolk was increased in all the PSM groups, while SFAs were only increased in the 0.6% PSM group. Among the indicators related to lipid metabolism, serum GLU decreased in all the PSM groups. The 0.6% PSM group had a reduction in serum and liver TG, as well as reductions in serum LDL-C and ALT. The same results were observed for the abdominal fat percentage in the 0.6% PSM group. Liver lipid metabolism-associated gene expression of FAS and LXRα was decreased in all the PSM groups, and the mRNA expression of ACC and SREBP-1c was significantly reduced in the 0.6% PSM group. HE staining showed that the vacuoles in the liver tissue gradually decreased with increasing PSM doses, especially the 1% PSM dose. Lipid droplets with a similar trend were observed using Oil Red O staining. In the results of the antioxidant capacity test, the serum T-AOC was increased in the 0.6% and 1% PSM groups, and the SOD in both the serum and liver was significantly increased in all the PSM groups. The expression of antioxidant-related genes such as Nrf2, NQO-1, HO-1, CAT and GSH-Px was significantly upregulated in the 1% PSM group. In conclusion, the PSM diet improved the lipid metabolism and antioxidant capacity of breeding hens. PSM reduces mortality and improves fertilization and hatchability in the late laying period of chickens, resulting in greater benefits. We recommend adding 0.6% PSM to layer feed, which improves the physical condition of the hens and brings higher economic benefits.

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.

Minimal effects of ultraviolet light supplementation on egg production, egg and bone quality, and health during early lay of laying hens

Chicken vision is sensitive to ultraviolet (UV) light containing the UVA spectrum, while UVB plays a key role in the endogenous production of vitamin D₃. However, commercially available light sources are typically deficient in the UV spectrum and thus may not adequately fulfill the lighting requirements of indoor-housed laying hens. We hypothesized that supplementary UVB light may improve egg production and egg quality, and bone health during early lay relative to UVA supplementation or standard control lighting. To investigate the effects of UV light supplementation, an experiment was conducted on 252 ISA Brown hens during 16 to 27 weeks of age. Birds were housed in eighteen pens (14 hens/pen) under three different light treatment groups each with six replications: (i) UVO: standard control lighting with LED white light, (ii) UVA: control lighting plus supplemental daylight with an avian bulb, and (iii) UVA/B: control lighting plus a supplemental full spectrum reptile bulb containing both UVA and UVB wavelengths. Hen-day egg production and egg quality, blood parameters including plasma Ca and P, and serum 25(OH)D₃, and hen body weight and external health scoring were measured at different age points; while bone quality was assessed at the end of the experiment at 27 weeks. Data were analyzed in JMP® 16.0 using general linear mixed models with α level set at 0.05. Results showed that UVA and UVA/B supplemented birds reached sexual maturity (50% production) 3 and 1 day earlier, respectively, than control birds. There was a trend for UV lights to increase hen-day egg production (P = 0.06). Among egg quality traits, only eggshell reflectivity and yolk index were affected by UV lights (P = 0.02 and 0.01, respectively); however, most of the egg quality traits changed over age (all P < 0.01). Post-hoc tests showed higher serum 25(OH)D₃ in the UVA/B group relative to control hens (P < 0.05); but there was no treatment effect on plasma Ca and P or on bone quality parameters (all P > 0.05). A significant interaction was observed between light treatment and age for the number of comb wounds (P = 0.0004), with the UV supplemented hens showing more comb wounds after 24 weeks. These results demonstrated that supplemental UVA/B light had minimal effects on egg production and egg quality, whereas, UVA/B exposure may increase vitamin D₃ synthesis during the early laying period. The optimum duration of exposure and level of intensity needs to be determined to ensure these benefits.

Estradiol-17ß Is Influenced by Age, Housing System, and Laying Performance in Genetically Divergent Laying Hens (Gallus gallus f.d.)

The estrogen estradiol-17ß is known as one of the major gonadal steroid hormones with different functions in reproduction. In this study we analyzed estradiol-17ß concentration in laying hens of four pure bred chicken laying lines at four different time intervals of the laying period (17th-19th week of age, 33rd-35th week of age, 49th-51st week of age, and 72nd week of age). The high performing white egg (WLA) and brown egg (BLA) layer lines as well as the low performing white (R11) and brown (L68) layer lines were kept in both single cages and a floor housing system. We investigated whether there were differences in estradiol -17ß concentrations between lines at different ages that could be related to selection for high egg production or phylogenetic origin of the animals, and whether there was an influence of housing conditions on estradiol-17ß. Estradiol-17ß concentrations differed between high and low performing layer lines at all time intervals studied. High performing hens showed higher estradiol-17ß concentrations compared to low performing hens. In all lines, highest estradiol-17ß concentration was measured at their 49th to their 51st week of age, whereas the peak of laying intensity was observed at their 33rd to their 35th week of age. Additionally, hens with fewer opportunities for activity housed in cages showed higher estradiol-17ß concentrations than hens kept in a floor housing system with more movement possibilities. We could show that laying performance is strongly linked with estradiol -17ß concentration. This concentration changes during laying period and is also influenced by the housing system.

The Diverse Roles of 17β-Estradiol in Non-Gonadal Tissues and Its Consequential Impact on Reproduction in Laying and Broiler Breeder Hens

Estradiol-17β (E2) has long been studied as the primary estrogen involved in sexual maturation of hens. Due to the oviparous nature of avian species, ovarian production of E2 has been indicated as the key steroid responsible for activating the formation of the eggshell and internal egg components in hens. This involves the integration and coordination between ovarian follicular development, liver metabolism and bone physiology to produce the follicle, yolk and albumen, and shell, respectively. However, the ability of E2 to be synthesized by non-gonadal tissues such as the skin, heart, muscle, liver, brain, adipose tissue, pancreas, and adrenal glands demonstrates the capability of this hormone to influence a variety of physiological processes. Thus, in this review, we intend to re-establish the role of E2 within these tissues and identify direct and indirect integration between the control of reproduction, metabolism, and bone physiology. Specifically, the sources of E2 and its activity in these tissues via the estrogen receptors (ERα, ERβ, GPR30) is described. This is followed by an update on the role of E2 during sexual differentiation of the embryo and maturation of the hen. We then also consider the implications of the recent discovery of additional E2 elevations during an extended laying cycle. Next, the specific roles of E2 in yolk formation and skeletal development are outlined. Finally, the consequences of altered E2 production in mature hens and the associated disorders are discussed. While these areas of study have been previously independently considered, this comprehensive review intends to highlight the critical roles played by E2 to alter and coordinate physiological processes in preparation for the laying cycle.