The effect of dietary calcium concentration and particle size on performance, eggshell quality, bone mechanical properties and tibia mineral contents in moulted laying hens

CYP24A1 and TRPC3 Gene Expression in Kidneys and Their Involvement in Calcium and Phosphate Metabolism in Laying Hens

Ca and P homeostasis across the egg-laying cycle is a complex process involving absorption in the small intestine, reabsorption/excretion in the kidneys, and eggshell gland secretion. Diets with inadequate calcium and phosphorus can interfere with their absorption and digestibility, resulting in eggshell quality losses and reduced productive life, affecting egg production and welfare. A better understanding of gene expression profiles in the kidneys of laying hens during the late egg-laying period could clarify the renal role in mineral metabolism at this late stage. Therefore, the performance, egg quality and bone integrity-related traits, and expression profiles of kidney candidate genes were evaluated in 73-week-old laying hens receiving different Ca and P ratios in their diet: a high Ca/P ratio (HR, 22.43), a low ratio (LR, 6.71), and a medium ratio (MR, 11.43). The laying hens receiving the HR diet had improved egg production and eggshell quality traits compared to the other two groups. Humerus length was shorter in the HR than in the other groups. The CYP24A1 and TRPC3 genes were differentially expressed (p.adj ≤ 0.05) among the groups. Therefore, their expression profiles could be involved in calcium and phosphate transcellular transport in 73-week-old laying hens as a way to keep mineral absorption at adequate levels.

Impact of Perch Provision Timing on Activity and Musculoskeletal Health of Laying Hens

Laying hens can experience a progressive increase in bone fragility due to the ongoing mobilization of calcium from bones for eggshell formation. Over time, this escalates their susceptibility to bone fracture, which can reduce their mobility and cause pain. The provision of perches as an exercise opportunity could potentially enhance bone strength, but the timing of exposure to perches during the birds' development may modulate its impact. The objective of this study was to investigate the enduring impacts of perch provision timing on the musculoskeletal health of laying hens. A total of 812 pullets were kept in different housing conditions (seven pens/treatment, 29 birds/pen) with either continuous access to multi-tier perches from 0 to 40 weeks of age (CP), no access to perches (NP), early access to perches during the rearing phase from 0 to 17 weeks of age (EP), or solely during the laying phase from 17 to 40 weeks of age (LP). At weeks 24, 36, and 40 of age (n = 84 birds/week), three birds per pen were monitored for individual activity level, and blood samples were collected from a separate set of three birds per pen to analyze serum levels of tartrate-resistant acid phosphatase 5b (TRACP-5b) and C-terminal telopeptide of type I collagen (CTX-I) as markers of bone demineralization. At 40 weeks of age, three birds per pen (n = 84) were euthanized for computed tomography scans to obtain tibial bone mineral density (BMD) and cross-sectional area (CSA) with further analysis including muscle deposition, tibial breaking strength, and tibial ash percent. During week 24, hens from CP, EP, and LP pens had the highest overall activity compared to hens from NP pens (p < 0.05) with no differences between treatments for overall activity level during weeks 36 or 40 (p > 0.05). During weeks 24, 36, and 40, hens from CP and LP pens showed greater vertical and less horizontal activity compared to hens from EP and NP pens (p < 0.05). TRACP-5b and CTX-I concentrations did not differ between treatments at week 24 of age (p > 0.05). Hens from CP pens had the lowest TRACP-5b and CTX-I concentrations at 36 weeks of age with EP and LP hens showing intermediate responses and NP hens having the highest concentration (p < 0.05). At 40 weeks of age, CP hens had the lowest TRACP-5b and CTX-I concentrations compared to NP hens (p < 0.05). Total bone CSA did not differ between treatments (p > 0.05), but CP had greater total BMD than NP (p < 0.05) with no differences between EP and LP treatments. CP and LP hens had larger biceps brachii, pectoralis major, and leg muscle groups as well as greater tibial breaking strengths than EP and NP treatments (p < 0.05). CP hens had higher tibial ash percentages compared to EP, LP, and NP (p < 0.05). Our results indicate that providing continuous perch access improves the musculoskeletal health and activity of laying hens at 40 weeks of age compared to no access and that late access to perches has a beneficial impact on activity, muscle deposition, and bone strength.

Influence of two levels of phytic acid and particle size of oyster shell on the performance, calcium digestibility, gastrointestinal pH, and bone traits in broilers

1. Phytic acid (PA) is an antinutritional factor in poultry diets. The effect of high dietary PA in chicken diets might be exacerbated when the particle size of oyster shell (OS) is too fine. Thus, this study investigated the hypothesis that high PA with fine OS particle size would impair growth in broilers.2. Two hundred and eighty Cobb 500 broilers were assigned to four diets in a 2 × 2 factorial arrangement in a CRD. The factors were PA (low or high) and OS particle size (fine or coarse) in starter, grower and finisher diets. Data collected were performance, Ca digestibility, gastrointestinal pH and bone traits.3. On d 21, high PA increased intake (P < 0.05), gain (P = 0.099) and body weight (BW; P = 0.093) compared to low PA. On d 42, high PA increased BW (P = 0.086) and gain (P = 0.089) compared to low PA. High PA increased intake (P = 0.063), BW (P = 0.054) and gain (P = 0.056) compared to low PA on d 56. High PA improved liveability on d 56 (P < 0.05) compared to low PA. In birds fed coarse OS, crop and ileal pH were reduced (P < 0.05) by high PA on d 28. The OS × PA interaction was observed for ileal pH (P < 0.05) on d 56, where in birds fed coarse OS, low PA increased ileal pH. Fine OS increased crop (P = 0.056) and proventriculus pH (P < 0.05) on d 56. There were no treatment effects on calcium digestibility. In birds fed fine OS, high PA decreased the BS (P < 0.05).4. Overall, the study showed that a combination of high PA and coarse OS particle size improves the production performance of broilers, while low PA and coarse OS improve their bone health.

Transcriptomic analysis of the liver in aged laying hens with different eggshell strength

Eggshell is composed of a very ordered and mineralized structure and is important for egg quality. Eggshell strength is particularly important because of its direct association with economic outcomes and egg safety. Various factors related to laying hens and their environment affects eggshell strength. However, the molecular mechanisms of liver functions related to decreased eggshell strength of aged laying hens are largely unknown. Therefore, this study aimed to identify potential factors affecting eggshell strength in aged laying hens at the hepatic transcriptomic level. A total of five hundred 92-wk-old Hy-line Brown laying hens were screened to select those exhibiting the greatest variation in eggshell strength. Based on the final eggshell strength, 12 hens producing eggs with strong eggshell strength (SES) and weak eggshell strength (WES) were finally selected (n = 6) for liver tissue sampling. The RNA-sequencing was performed to identify differentially expressed genes (DEGs) between the 2 groups. We identified a total of 2,084 DEGs, of which 1,358 genes were upregulated and 726 genes were downregulated in the WES group compared with SES group. According to the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, the DEGs indicated the mammalian target of rapamycin signaling pathway, the Janus kinase-signal transducer and activator of transcription pathway, the mitogen‑activated protein kinase signaling pathway, and the insulin resistance pathways. Genes related to fatty liver disease were upregulated in WES group compared with SES group. In addition, expression of several genes associated with oxidative stress and bone resorption activity was altered in aged laying hens with different eggshell strength. Overall, these findings contribute to the identification of genes involved in different intensity of eggshell strength, enabling more understanding of the hepatic molecular mechanism underlying in decreased eggshell strength of aged laying hens.

Dietary zinc supplementation affects eggshell quality and ultrastructure in commercial laying ducks by influencing calcium metabolism

This study evaluated dietary Zn supplementation on productive performance, eggshell quality and ultrastructure, and calcium metabolism during eggshell formation in laying ducks. A total of 360 Longyan laying ducks (45-wk) were randomly divided into 5 treatment groups with 6 replicates of 12 birds each and fed for 20 wk. The 6 treatments fed the basal diet supplemented with 0 (control), 20, 40, 80, or 160 mg Zn/kg (ZnSO4·H2O). Dietary supplemental level at 80 mg/kg increased egg production (4.3%) and mass (5.7%), and decreased FCR (2.9%) compared to the basal diet, and these indices increased quadratically with increasing Zn supplemental levels (P < 0.05). The shell breaking strength (15.8%) and fracture toughness (10.6%) were higher with the supplementation of Zn at 80 mg/kg than the basal diet, and increased quadratically with Zn supplementation (P < 0.05). Dietary supplementation of Zn at 80 mg/kg improved shell ultrastructure by increasing total (9.0%) and effective thickness (14.2%) and decreasing mammillary thickness (12.0%), and their responses were quadratic with increasing Zn levels (P < 0.05). The supplementation of Zn affected the calcium contents in plasma, tibias and ulna, ulna phosphorus content, and linear and quadratic effects were observed, and higher values were observed with 160 mg/kg Zn supplementation than control (P < 0.05). The supplemental Zn level at 80 mg/kg increased shell effective thickness in growth stage (P < 0.05), and shell calcium and phosphorus content in initial and growth stages (P < 0.05). Dietary Zn supplementation did not affect the gene expression of Ca2+ transporters in the eggshell gland, but affected the expression of HCO3- exchanger in initial and growth stage (P < 0.05). Overall, dietary Zn supplementation could improve productive performance and shell quality in laying ducks at late phase of production, and calcium metabolism and deposition were modulated by Zn influencing HCO3- secretion and thus affecting shell ultrastructure and quality. A supplemental level of 80 mg/kg Zn in the diet with a basal content of 34.0 mg/kg was optimal, and higher level (160 mg/kg) decreased shell calcium deposition by depressing its metabolism.

The Response of Layer Hen Productivity and Egg Quality to an Additional Limestone Source When Offered Diets Differing in Calcium Concentrations and the Inclusion of Phytase

Simple Summary

Dietary calcium is essential for optimal egg production and quality in laying hens, but high concentrations can impede the digestibility of other dietary components. The provision of limestone grit in addition to the main diet may help maintain overall calcium intake while allowing a reduction in dietary calcium levels. The impact of phytase, an enzyme that increases calcium availability in the gut, on the voluntary consumption of limestone grit is unknown. Here, the capacity for hens with access to a separate limestone grit source to modify Ca consumption when offered varying dietary Ca levels and phytase was evaluated. Dietary phytase reduced limestone grit consumption. Egg production was unaffected by reducing dietary calcium levels or the phytase addition. Eggshell measurements worsened in line with decreasing dietary calcium levels despite the provision of limestone grit. In summary, the provision of limestone grit resulted in comparable egg production but not eggshell quality in hens offered suboptimal levels of dietary calcium.

Abstract

Laying hens require substantial quantities of calcium (Ca) to maintain egg production. However, maintaining recommended dietary Ca through inclusion of limestone may impede nutrient digestibility, including that of other minerals. It was hypothesized that providing a separate source of dietary Ca in the form of limestone grit would preserve Ca intake of hens offered diets containing suboptimal Ca concentrations. Furthermore, the impact of dietary phytase at a “superdosing” inclusion rate on the voluntary consumption of limestone grit was evaluated. One hundred and forty-four laying hens (19 weeks of age) were assigned to one of six dietary treatments in a 3 × 2 factorial arrangement comprising three dietary Ca concentrations (40, 30, and 20 g/kg) and ±dietary phytase (3500 FYT/kg diet) on an ad libitum basis for six weeks. Limestone grit (3.4 ± 1.0 mm) was provided to all hens ad libitum. Hens offered diets containing phytase consumed significantly less limestone grit p = 0.024). Egg weight, rate of lay, and egg mass were unaffected by dietary treatment (p > 0.05). Egg shell weight % (p < 0.001), shell thickness (p < 0.001), and shell breaking strength (p < 0.01) decreased in line with dietary Ca levels. In summary, dietary superdosing with phytase reduced the consumption of a separate limestone source in individually housed, early lay ISA Brown hens. Egg shell quality variables but not egg production worsened in line with lower dietary Ca levels.

Superiority of coarse eggshell as a calcium source over limestone, cockle shell, oyster shell, and fine eggshell in old laying hens

Chicken eggshell (ES) waste is a rich source of calcium carbonate (CaCO3); however, the potential of ES as dietary calcium (Ca) in old laying hens has not been explored. This study compared the effects of feeding limestone, cockle shell, oyster shell, fine ES, and coarse ES as the sole Ca source on production performance, egg quality, blood biochemical constituents, and tibia characteristics in old laying hens. A total of 450 ISA-Brown laying hens at 73 wk of age with similar egg production rate (EPR) were randomly assigned to 5 treatment groups (90 hens/group, 9 hens/replicate) for 7 wk. Dietary treatment groups comprised a corn-soybean meal based diet containing different Ca sources: (i) limestone (LS; < 2 mm and 2-4 mm mixed in the ratio of 3:7) as control, (ii) cockle shell (CS; 1-4 mm), (iii) oyster shell (OS; 3-16 mm), (iv) ES fine particles (ESF; < 1 mm), and (v) ES coarse particles (ESC; 3-5 mm). Results indicated that dietary inclusion of coarse ES particles significantly increased average egg weight (P < 0.001) and daily egg mass (P < 0.05), and decreased feed conversion ratio (P < 0.001) as compared with the other treatments. However, no significant differences in EPR, feed intake, cracked egg proportion, and mortality were observed among the dietary treatments (P > 0.05). Notably, the use of ESF led to a lower proportion of cracked eggs than ESC (P < 0.05). ESC fed hens produced the heaviest eggs whereas CS fed hens produced the lightest (P < 0.001); the particle size of ES also affected the egg weight (P < 0.05). The eggs from OS and ESC fed hens showed a greater albumen height in comparison to eggs from CS group (P < 0.05); but no significant difference was observed among the LS, OS, ESF, and ESC groups (P > 0.05). The yolk color was darker in the eggs of group ESF as compared with other dietary groups (P < 0.01). However, no significant effects on Haugh units and shell properties were observed among the treatments (P > 0.05). The blood biochemistry results were not affected by the dietary Ca (P > 0.05) except for lower levels of high-density lipoprotein percentage (HDL %) in OS and ESC fed hens (P < 0.05). The tibia characteristics including weight, length, width, and breaking strength did not differ among the dietary groups (P > 0.05). However, the ESC and OS fed hens showed higher tibia bone mineral density (BMD) than the other groups (P < 0.001). In conclusion, coarse ES as a sole Ca source had beneficial effects on the production performance, egg quality, and tibia BMD in old laying hens.

Prolonged scotophase within a 24 hour light regime improves eggshell quality by enhancing calcium deposition in laying hens

Calcium (Ca) and phosphorus (P) transporters are responsible for their absorption and transport in small intestine and kidney, contributing to eggshell formation. The light-dark cycle is a primary cue in the reproduction of laying hen. In this study, we investigated the effect of different light-dark programs on eggshell quality and the expression of genes related to Ca and P transportation in laying hens. Seventy-two 56-week-old laying hens were randomly divided into two groups and reared at 16-h light and 8-h dark (control) or 9-h light and 15-h dark regime (long dark phase, LDP). The expressions of calcium transporter calbindin-D28k (CaBP-D28k), plasma membrane Ca ATPase 1b (PMCA1b), and phosphorus transporter NaPi-IIb (NPt2b) and NaPi-IIa (NPt2a) were measured in the small intestine, kidney, and eggshell gland. The results showed that feed intake (P < 0.001) and egg weight (P = 0.05) were decreased by LDP treatment. Compared with control, the eggshell hardness was increased (P = 0.011) by LDP treatment, but the eggshell thickness and the percentage of eggshell were not changed. The Ca and P contents in eggshell were increased by LDP treatment. During the scotophase, LDP-hens showed higher serum Ca (P = 0.0056) and P levels (P = 0.079) but lower alkaline phosphatase (ALP) activity than that of control hens. In the duodenum, the relative higher expression of CaBP-D28k and PMCA1b in scotophase compared to photophase was masked by LDP treatment. The expression of CaBP-D28k and osteopontin (OPN) in the eggshell gland were increased by LDP treatment, compared to control hens. In the jejunum, the protein expression levels of CaBP-D28k and PMCA1b decreased during photophase in LDP-hens. The result indicates that the increased blood Ca and P concentration during scotophase by LPD treatment is beneficial to the deposition of Ca and P in the eggshell. The result offers an alternative strategy for managing laying hens with poor eggshell quality.

Molecular distribution and localization of extracellular calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) at three different laying stages in laying hens (Gallus gallus domesticus)

The extracellular calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) play important roles in regulating calcium mobilization, calcium absorption, and calcium homeostasis, and they could be potential therapeutic targets to osteoporosis in laying hens. The present study investigated the molecular distribution of CaSR and VDR and the localization of CaSR in the kidney, proventriculus (true stomach), duodenum, jejunum, ileum, colon, cecum, shell gland, and tibia of laying hens at 3 different laying stages (19, 40, and 55 wk). The results showed that the relative mRNA abundance of CaSR in the kidney, ileum, proventriculus, duodenum, and colon was higher (P < 0.05) than the other tissues at 40 and 55 wk. The relative mRNA abundance of CaSR in the tibia was higher (P < 0.05) at 55 wk than at 40 wk. However, there were no significant differences in the relative protein abundance of CaSR among all tested tissues at peak production or in each tissue at the 3 different laying stages (P > 0.05). The relative mRNA abundance of VDR was higher (P < 0.05) in the small intestine (duodenum, jejunum, and ileum) when compared with other tissues at the 3 different laying stages. The relative protein abundance of VDR in the duodenum was higher (P < 0.05) than that in the proventriculus, colon, and cecum. There were no significant differences in the VDR expression among the tested tissues at the 3 different laying stages (P > 0.05). The immunohistochemical results showed that the positive staining was found widely in each tissue. Moreover, different laying stages did not affect the localization of CaSR except for the tibia tissue. In conclusion, similar to VDR, CaSR was widely expressed not only in the gut but also in the tibia and shell gland in laying hens. The expression level of CaSR and VDR in all tested tissues was unchanged at the different laying stages.

Combined Effect of Genotype, Housing System, and Calcium on Performance and Eggshell Quality of Laying Hens

Simple Summary

Hen performance and eggshell quality are affected by a wide range of factors from which genotype. The housing conditions and feed calcium (Ca) level might be considered the most important. Here, we compared the performance and eggshell quality of commercial hybrids (ISA Brown, Bovans Brown) and traditional Czech hybrid (Moravia BSL). Laying hens were housed in enriched cages and on littered pens and fed two different Ca levels (3.00% vs. 3.50%). Contrary to the commercial hybrids, Moravia BSL performed better under the lower feed Ca level in enriched cages. Additionally, the data pointed out the importance of studying the interaction between factors, which might help to decide the best housing system and feed Ca level for a certain hen genotype.

Abstract

The objective of this study was to evaluate hen performance and eggshell quality response to genotype, housing system, and feed calcium (Ca) level. For this purpose, an experiment was conducted on 360 laying hens of ISA Brown, Bovans Brown (commercial hybrids), and Moravia BSL (traditional Czech hybrid). Laying hens were kept in enriched cages and on littered floor and fed similar feed mixtures with different Ca content (3.00% vs. 3.50%). In terms of hen performance, ISA Brown had the highest egg production (84.2%) compared to Moravia BSL (74.3%) and Bovans Brown (71.4%). Regarding eggshell quality, Bovans Brown showed the highest values of all eggshell quality parameters. Increasing feed Ca level augmented egg production (p ≤ 0.001) but had no effect on other performance parameters. Except eggshell thickness, all eggshell quality parameters were affected by the three-way interaction of genotype, housing, and Ca. Bovans Brown, which had the strongest eggshells (5089 g/cm²) when housed on a littered floor system and fed 3.00% Ca, while Moravia BSL housed on a littered floor had the weakest eggshells (4236 g/cm²) at 3.50% Ca. The study pointed out the importance of the interactions between studied factors on performance and eggshell quality compared to an individual factor effect.

Dietary supplementation with protected calcium effects production and egg quality of Hy-line brown laying hens

Context Currently, the commonly used dietary calcium sources are not sufficiently bioavailable to be used for eggshell formation or bone health in laying hens. Protected calcium, a blend of calcium and medium-chain fatty acids with matrix coating, may exert an effective absorption and metabolism ability for calcium consumption in the laying hen. Aims The present study was conducted to evaluate the effects of protected-calcium supplementation on egg production, egg quality, and serum calcium and phosphorus concentrations in laying hens. Methods In total, 144 Hy-line brown laying hens (25 weeks old) were randomly allotted to three treatments (8 replicates with 6 hens, 1 hen per cage) in a 10-week trial. Treatments consisted of corn–wheat–soybean meal-based basal diet with limestone (coarse limestone:fine limestone = 50:50) as a calcium source (CON) or basal diet supplemented with 0.5% (P1) or 1% (P2) protected calcium in substitution for an equal quantity of coarse limestone. Data were statistically analysed using linear and quadratic contrast with the GLM procedure of SAS. Probability values of &lt;0.05 indicate significance. Key results At Weeks 31–33 and 35, the cracked-egg rates were lower in the P1 and P2 groups than in the CON group (P &lt; 0.05; linear, P &lt; 0.05) and, at Weeks 29 and 34, the cracked-egg rates in the P2 group were also significantly (P &lt; 0.05) decreased. At Weeks 26, 30 and 32, the Haugh units in the P2 group were significantly (P &lt; 0.05) higher than those in the CON group. In addition, eggshell strength was increased significantly (P &lt; 0.05) in the P2 group at Weeks 26, 27 and 31–35. The serum calcium concentration of the P2 group was significantly (P &lt; 0.05) greater than that of the CON group in the morning. Conclusions In conclusion, a replacement of limestone with 1% protected calcium can increase eggshell quality. Implications Protected-calcium supplementation can be used in practice for decreasing the breakage of eggs.

Long-term effects of Buttiauxella sp. phytase on performance, eggshell quality, apparent ileal Ca and P digestibility, and bone properties of white egg layers

Adequate dietary Ca and available phosphorus (avP) are essential to long-term egg production and bone health in laying hens. The effects of dietary Ca and avP levels and Buttiauxella sp. phytase (BSP) were studied in Lohmann LSL Lite hens from 30 to 70 wk of age (woa). Hens (n = 456; 4 per cage) were fed either a primary breeder recommendation-based diet (positive control; PC); the PC with avP and Ca levels reduced by 0.146 and 0.134% of the diet, respectively, without (NC) or with 300 FTU/kg BSP (NC+BSP). Egg production, BW, feed intake, FCR, and eggshell quality from 30 to 70 woa, and apparent ileal digestibility of P (AIDP) and Ca (AIDCa), and bone quality at 32, 48, and 70 woa were measured. The avP and Ca levels in the NC diet were not clinically deficient, as most parameters were unaffected by diet. Hen BW from 34 to 70 woa tended to be 2.9% greater (P = 0.076) for PC and NC+BSP compared to NC. Mid-diaphysis cortical bone mineral content (CBMC) tended to be 10% and 9% higher (P = 0.065) in the NC+BSP hens than in NC hens at 48 and 70 woa, respectively. AIDP of NC+BSP was 24% greater (P = 0.034) than of NC at 32 woa and tended to be 18% greater (P = 0.082) than AIDP of PC at 48 woa, and 25% lower than of NC and PC at 70 woa (P = 0.028). AIDCa was 25% lower for NC+BSP than PC at 48 woa only (P = 0.037). The avP and Ca sufficiency in the NC diet limited the opportunity to determine a phytase effect. Although the supplemental BSP tended to increase BW and 48 and 70 woa CBMC, and increased 32 woa AIDP, the efficacy of BSP could not be determined due to the lack of an NC effect on most parameters. Commercial laying hens can maintain health and productivity at lower than recommended levels of dietary Ca and avP; phytase supplementation may allow for even further reductions.

Effects of pre-lay dietary calcium (2.5 vs. 4.0%) and pullet strain (Lohmann Brown vs. Selected Leghorn LSL-Lite) on calcium utilization and femur quality at 1st through to the 50th egg2

To study the effects of pre-lay dietary Ca and strain on Ca utilization and femur quality at 1st through to 50th egg, 30 Lohmann Brown (LB) and 30 Lohmann Selected Leghorn-Lite (LSL) pullets (14 weeks of age, woa) reared under same management regimen were used. Six pullets/strain were necropsied for baseline femur samples and the rest (24 pullets/strain) placed in individual cages (65 × 30 × 45 cm3) and fed 1% Ca developer diet for 2 wk. At 16 woa, all pullets were weighed and allocated within strains to pre-lay diets (2.5 vs. 4.0% Ca) effectively creating a 2 × 2 factorial arrangement. The pullets were offered pre-lay diets for 2 wk and switched to 4% Ca diet at 18 woa. The diets contained TiO2 to determine apparent retention (AR) of Ca. The age, BW, and feed intake (FI) at 1st, 25th, and 50th egg were recorded. Excreta samples were taken during pre-lay, at 1st and 25th egg and 4 hens per treatment were necropsied for femur samples at 1st, 25th, and 50th egg. There was no interaction (P > 0.05) between pre-lay Ca and strain on Ca intake, femur mineral density (FMD), mineral content (FMC), breaking strength (FBS), and ash (FA) content at 1st, 25th, and 50th egg. At 1st egg, pre-lay Ca interacted with strain on AR of Ca (P = 0.014) such that LB hens retained more Ca at 2.5 vs. 4.0% Ca or LSL at 2.5% Ca. Pre-lay Ca had no effect (P > 0.05) on FMD, FMC, FBS, and FA at 1st, 25th, and 50th egg lay. Compared with LB hens, LSL hens had higher FMD (0.30 vs. 0.19 g/cm2; P = 0.010) and FA (51.9 vs. 42.5%; P < 0.01) at 1st egg and FBS (259.4 vs. 173.8 N, P < 0.01) at 25th egg. In conclusion, except at 25th egg, pre-lay Ca and strain had independent effect on Ca utilization. Femur attributes to 1st egg suggested innate need for LSL birds to accumulate critical bone mass prior to first oviposition.

Estimation of calcium requirements for optimal productive and reproductive performance, eggshell and tibial quality in egg-type duck breeders

Optimizing the dietary calcium (Ca) level is essential to maximize the eggshell quality, egg production and bone formation in poultry. This study aimed to establish the Ca requirements of egg-type duck breeders from 23 to 57 weeks of age on egg production, eggshell, incubation, tibial, plasma and ovary-related indices, as well as the expression of matrix protein-related genes. Totally, 450 Longyan duck breeders aged 21 weeks of age were allotted randomly into five treatments, each with six replicates of 15 individually caged birds. The data collection started from 23 weeks of age and continued over the following 35 weeks. The five groups corresponded to five dietary treatments containing either 2.8%, 3.2%, 3.6%, 4.0% or 4.4% Ca. The tested dietary Ca levels increased (linear, P <0.01) egg production and egg mass, and linearly improved (P <0.01) the feed conversion ratio (FCR). Increasing the dietary Ca levels from 2.8% to 4.4% increased (P <0.01) the eggshell thickness and eggshell content. The tested Ca levels showed a quadratic effect on eggshell thickness and ovarian weight (P <0.01); the highest values were obtained with the Ca levels 4.0% and 3.6%, respectively. Dietary Ca levels affected the small yellow follicles (SYF) number and SYF weight/ovarian weight, and the linear response (P <0.01) was significant vis-à-vis SYF number. In addition, dietary Ca levels increased (P <0.05) the tibial dry weight, breaking strength, mineral density and ash content. Plasma and tibial phosphorus concentration exhibited a quadratic (P <0.01) response to dietary Ca levels. Plasma calcitonin concentration linearly (P <0.01) increased as dietary Ca levels increased. The relative expression of carbonic anhydrase 2 in the uterus rose (P <0.01) with the increment of dietary Ca levels, and the highest value was obtained with 3.2% Ca. In conclusion, Longyan duck breeders fed a diet with 4.0% Ca had superior eggshell and tibial quality, while those fed a diet with 3.6% Ca had the heaviest ovarian weights. The regression model indicated that the dietary Ca levels 3.86%, 3.48% and 4.00% are optimal levels to obtain maximum eggshell thickness, ovarian weight and tibial mineral density, respectively.

Effect of different split-feeding treatments on performance, egg quality, and bone quality of individually housed aged laying hens

In order to try to combat the effect of age on eggshell quality in aged laying hens, 5 split-feeding treatments were compared with conventional feeding between 75 and 92 wk of age. In the conventional treatment (T1), the same morning (M) and afternoon (A) diet was fed containing fine (FL) and coarse (CL) limestone at a 50:50 ratio. In the split treatments, the ratio of FL and CL was 50:50 or 30:70, and time of administration (M/A) differed. The following treatments were given: T2 = 50FL-M:50CL-A, T3 = 50CL-M:50FL-A, T4 = 30FL-M:20FL-A+50CL-A, T5 = 30FL-M:70CL-A, and T6 = 0M:30FL-A+70CL-A. A total of 12 individually housed Dekalb white hens was used per treatment. Feed intake, nutrient intake, and laying % was lower in T1 compared to all split treatments (P ≤ 0.001). Due to this low performance in T1, split feeding could not be compared to the conventional system in this trial. By the end of the trial, eggshell quality was improved in T1 as a result of low laying % and more frequent and longer laying pauses. In the split treatments, laying % and feed intake were similar, except in T3 in which a decrease was observed after 81 wk (P ≤ 0.05). Egg weight was higher in T5 and T6 due to higher total and morning protein intake compared to T3 (P ≤ 0.05). Feeding only 50FL-A in T3 not only resulted in lower performance but also in consistently lower shell thickness, indicating a negative effect of suboptimal limestone supplementation. In the split-feeding system, the most optimal combination of morning and afternoon diet was a morning diet with only FL and an afternoon diet with only CL (T2), which both provided ∼50% of the total daily Ca intake. Shell breaking strength and dynamic stiffness could be maintained on this diet between 75 and 92 weeks. Decreasing the amount of Ca in the morning and increasing it in the afternoon did not improve shell quality traits. Bone quality was not affected by limestone particle size or inclusion level in the split-feeding system.

Opportunities for exercise during pullet rearing, Part II: Long-term effects on bone characteristics of adult laying hens at the end-of-lay

Osteoporosis in laying hens has been a production and welfare concern for several decades. The objective of this study was to determine whether differing opportunities for exercise during pullet rearing influences long-term bone quality characteristics in end-of-lay hens. A secondary objective was to assess whether differing opportunities for exercise in adult housing systems alters bone quality characteristics in end-of-lay hens. Four flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30-bird furnished cages (FC-S), or 60-bird furnished cages (FC-L) for adult housing. Wing and leg bones were collected at the end-of-lay to quantify bone composition and strength using quantitative computed tomography and bone breaking strength (BBS). At the end-of-lay, Avi hens had greater total and cortical cross-sectional area (P < 0.05) for the radius and tibia, greater total bone mineral content of the radius (P < 0.001), and greater tibial cortical bone mineral content (P = 0.029) than the Conv hens; however, total bone mineral density of the radius (P < 0.001) and cortical bone mineral density of the radius and tibia (P < 0.001) were greater in the Conv hens. Hens in the FC-L had greater total bone mineral density for the radius and tibia (P < 0.05) and greater trabecular bone mineral density for the radius (P = 0.027), compared to hens in the FC-S and CC. Total bone mineral content of the tibia (P = 0.030) and cortical bone mineral content of the radius (P = 0.030) and tibia (P = 0.013) were greater in the FC-L compared to the CC. The humerus of Conv hens had greater BBS than the Avi hens (P < 0.001), and the tibiae of FC-L and FC-S hens had greater BBS than CC hens (P = 0.006). Increased opportunities for exercise offered by the aviary rearing system provided improved bone quality characteristics lasting through to the end-of-lay.

Effect of selected feed additives on egg performance and eggshell quality in laying hens fed a diet with standard or decreased calcium content

The aim of the experiment with 240 ISA Brown hens fed the diets with standard or decreased Ca level was to evaluate the effect of selected feed additives on laying performance and eggshell quality. The hens were allocated to 10 treatments, each containing 12 cages (replicates) of 2 birds. A 2 × 5 experimental arrangement was used. From 26 to 70 wks of age, experimental diets containing 3.20 or 3.70% Ca were used. The diets were either not supplemented, or supplemented with sodium butyrate, probiotic bacteria, herb extracts blend or chitosan. The decreased dietary Ca reduced eggshell quality indices in older hens (43-69 wks) (P<0.05) without effect on performance indices. The addition of the probiotic, herb extracts, or chitosan increased the laying rate (P<0.05). In older hens, i.e. at 69 wk, chitosan increased eggshell thickness and breaking strength, while herb extracts increased eggshell thickness (P<0.05). There was no interaction between the experimental factors in performance and eggshell quality. The used feed additives had no influence on fatty acid profile of egg lipids, however diet supplementation with chitosan decreased cholesterol concentration in egg yolk lipids (P<0.05). It can be concluded that such feed additives as probiotic, herb extracts, or chitosan may positively affect performance and eggshell quality, irrespective of Ca dietary level.

Effects of Dietary Calcium Levels on Productive Performance, Eggshell Quality and Overall Calcium Status in Aged Laying Hens

This study was conducted to investigate the effects of diets with varying levels of calcium on egg production, shell quality and overall calcium status in aged laying hens. A total of five hundred 70-wk-old Hy-Line Brown layers were divided five groups and fed one of the five experimental diets with 3.5%, 3.8%, 4.1%, 4.4%, or 4.7% Ca, for 10 weeks. There were no significant differences in feed intake, egg production and egg weight among groups. The cracked eggs were linearly reduced as dietary Ca levels increased to 4.7% (p<0.01). A significant linear improvement for eggshell strength and thickness were determined with increasing dietary Ca levels (p<0.01). The contents of serum Ca and phosphorus were not affected by dietary Ca levels. With increase in dietary Ca levels, the tibial breaking strength slightly increased. There were no significant differences in the tibial contents of ash, Ca and phosphorus among groups. In conclusion, eggshell quality, as measured by appearance, strength and thickness of eggshell, were influenced by dietary Ca content as expected (p<0.05). These results suggested that aged laying hens require relatively higher level of Ca than required levels from current Korean feeding standards for poultry.

Effects on performance and eggshell quality of particle size of calcium sources in laying hens' diets with different Ca concentrations

Abstract. The objective of this study was to evaluate the effect of particle size of a dietary Ca source on egg production and eggshell quality when added to hens' diets that have different levels of calcium. The experiment was carried out on 216 ISA Brown hens (25 to 70 weeks of age), allocated to 9 groups of 12 replicates (cages), with two birds in each cage. A 3 × 3 factorial arrangement was used, with three dietary levels of calcium (3.20, 3.70 and 4.20 %) and three levels of dietary substitutions (0, 25 and 50 %) of fine particles of limestone (FPL, diameter 0.2–0.6 mm) with large particles of limestone (LPL, diameter 1.0–1.4 mm) as a Ca source. The level of Ca in the diet had no effect on egg production, mean egg weight, feed intake, feed conversion ratio or eggshell quality parameters (P > 0.05). Substitution of FPL with LPL did not affect laying performance indices or eggshell quality at 30, 43 and 53 weeks of age (P > 0.05); however, it increased (P < 0.05) eggshell percentage, thickness, density and breaking strength in older hens (69 weeks of age). In conclusion, the results of this study demonstrated that a level of 3.20 % Ca in a layer's diet is sufficient through the entire laying cycle to maintain good egg production and eggshell quality and that partial (25 or 50 %) substitution of fine- with large-particle limestone can, irrespective of the level of Ca in the diet, improve eggshell quality in aged laying hens.