Re-evaluation of calcium and phosphorus requirements in aged laying hens

Marine red yeast supplementation improves laying performance by regulating small intestinal homeostasis in aging chickens

Recent studies have shown that age-related aging evolution is accompanied by imbalances in intestinal homeostasis. Marine red yeast (MRY) is a functional probiotic that has been shown to have antioxidant, immune and other properties. Therefore, we chose 900 healthy Hy-Line Brown hens at 433 d old as the research subjects and evaluated the correlation between intestinal health, laying performance, and egg quality in aged hens through the supplementation of MRY. These laying hens were assigned into 5 groups and received diet supplementation with 0%, 0.5%, 1.0%, 1.5%, and 2% MRY for 12 weeks. The results showed that MRY supplementation increased egg production rate, average egg weight, and egg quality, and decreased feed conversion ratio and daily feed intake (P < 0.05). The MRY supplement improved antioxidant indicators such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), stimulated villus height, and increased the villus height to crypt depth ratio (V/C ratio) in the intestine (P < 0.05). It also regulated the expression of intestinal inflammatory factors (transforming growth factor-β [TGF-β], interleukin [IL]-1β, IL-8, tumor necrosis factor-α [TNF-α]) while increasing serum immunoglobulin G (IgG) levels (P < 0.05). Furthermore, MRY supplementation upregulated the mRNA expression of tight junction proteins (occludin and zonula occludens-1 [ZO-1]), anti-apoptotic gene (Bcl-2), and autophagy-related proteins (beclin-1 and light chain 3I [LC3I]) in the intestine (P < 0.05). The MRY supplement also led to an increase in the concentration of short-chain fatty acids in the cecum, and the relative abundance of the phylum Bacteroidetes, and genera Bacteroides and Rikenellaceae_RC9_gut_group. The LEfSe analysis revealed an enrichment of Sutterella and Akkermansia muciniphila. In conclusion, the results of this experiment indicated that the additional supplementation of MRY can improve the production performance of laying hens and may contribute to the restoration and balance of intestinal homeostasis, which supports the application potential of MRY as a green and efficient feed additive for improving the laying performance in chickens.

Laying hen responses to multi-strain Bacillus-based probiotic supplementation from 25 to 37 weeks of age

OBJECTIVE

This study aimed to investigate the efficacy of Bacillus-based probiotics supplemented at two different levels to modulate the productive performance, egg quality, tibia traits, and specific cecal bacteria counts of Hy-Line Brown layers from 25 to 37 weeks of age.

METHODS

A total of 216 twenty-five-week-old hens were randomly distributed into 3 experimental diets with 12 replicates of 6 birds per cage. Diets included basal diet supplemented with 0 (CON), 3×108 (PRO1), or 3×109 (PRO2) colony-forming unit (CFU) of the test probiotic containing Bacillus subtilis PB6, Bacillus subtilis FXA, and Bacillus licheniformis G3 per kilogram of feed.

RESULTS

Improved egg weights and mass at 29 weeks; and feed intake at 31 weeks (p<0.10) were noticed with the probiotic-supplemented PRO1 and PRO2 diets. Considering egg quality, the shell thickness, Haugh units, and yolk color were improved; but yolk cholesterol was lowered (p<0.05) with PRO1 and PRO2 diets at 29 weeks. At both 33 and 37 weeks, the egg-breaking strength, shell color and thickness, albumen height, Haugh units, and yolk color were improved; but yolk cholesterol was similarly lowered (p<0.05) with the PRO1 and PRO2 diets. Improved tibia Ca, ash, weights, and density; and raised cecal counts of Bifidobacteria and Lactobacilli (p<0.05) were noticed with PRO1 and PRO2 diets. Improved tibia P but reduced Clostridia counts (p<0.10) were also observed with the PRO1 and PRO2 diets.

CONCLUSION

Probiotic supplementation of Bacillus subtilis PB6, Bacillus subtilis FXA, and Bacillus licheniformis G3 at 3×108 CFU/kg of feed is adequate to significantly improve egg quality, lower yolk cholesterol, enhance several tibia traits, and raise the populations of beneficial cecal bacteria. Modest improvements in several productive parameters and tibia P but reduced Clostridia were also observed; and could warrant further investigation of probiotic effects beyond the current test period.

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.

Dietary non-phytate phosphorus requirements for optimal productive and reproductive performance, and egg and tibial quality in egg-type duck breeders

Optimal dietary non-phytate phosphorus (NPP) is essential in poultry to maximise productive and reproductive performance, along with indices of egg and bone quality. This study aimed to establish the NPP requirements of egg-type duck breeders aged from 54 to 80 weeks on the following traits: egg production, egg incubation, egg quality, tibial characteristics, reproductive organ, plasma indices, and the expression of genes related to phosphorus absorption. Longyan duck breeders aged 54 weeks (n = 300) were randomly allotted to five treatments, each containing six replicates of 10 individually caged birds. Birds were fed corn-soybean meal-based diets containing 0.18, 0.25, 0.32, 0.38, and 0.45% NPP/kg for 27 weeks. The tested dietary NPP levels did not affect egg production or egg quality indices. The hatchling weight of ducklings increased (quadratic, P < 0.01) as dietary NPP level increased, and the highest value occurred with 0.25% NPP. The number of large yellow follicles (LYF), and the relative weights of LYF and ovary showed linear and quadratic responses to dietary NPP levels; the lowest number and relative weight of LYF occurred with 0.38% NPP, and the lowest ovarian weight was obtained with 0.25% NPP. There were no differences in tibial length, breaking strength, and mineral density in response to dietary NPP levels. In contrast, tibial content of Ca increased (linear, P < 0.01) with dietary NPP levels increasing from 0.18 to 0.45%, and the tibial content of P increased at 0.32% NPP and the higher dietary NPP levels. Plasma concentration of P showed a quadratic (P < 0.05) response to the dietary NPP levels, where the highest value was seen at 0.38% NPP. In conclusion, dietary NPP levels from 0.18 to 0.45% had no effects on egg production, and egg and tibial quality of duck breeders. The duck breeders fed a diet with 0.25% NPP showed the highest hatchling weight of their offspring, while those fed 0.38% NPP had the lowest number and relative weight of LYF. These results indicated that the diet with 0.25% NPP can be used in egg-type duck breeders to improve the hatchling weight of their offspring, without adverse effects on their productivity. The regression model indicated that the maximal hatchling weight of ducklings was obtained from duck breeders fed the diet with 0.30% NPP.

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.

Effects of feeding strategies on eggshell quality of laying hens during late laying period

Insufficient calcium supply during the dark period is an important reason for deteriorated eggshell quality in laying hens. In the present study, the feeding time of hens was altered in order to investigate whether the changes in feeding time and feed consumption could influence the laying performance and eggshell quality of hens. A total of 192, 60-wk-old Hy-line Brown hens with similar body weight and laying rate were obtained. The hens were randomly divided into 4 groups and subjected to the following feeding strategies: feeding 3 times a day (control group, CON), or feeding once a day in the morning at 08:00 (MF), in the noon at 12:00 (NF), or in the afternoon at 16:00 (AF), respectively. The feeding strategies had no significant effect (P > 0.05) on laying rate, egg weight, and egg mass. Although the feed intake did not differ among treatments, the time phase of feed consumption was changed. From 15:00 to 21:00 h, hens consumed 49.7%, 42.4%, 49.1%, and 70.8% of daily feed intake in the CON, MF, NF, and AF groups, respectively. Feeding strategy had no detectable influence (P > 0.05) on egg shape index, eggshell strength, and eggshell percentage. Compared to CON, AF hens tended to have a higher eggshell thickness (P = 0.053). In MF and NF treatments, plasma calcium (Ca), phosphorus (P) levels, and alkaline phosphatase (ALP) activity did not differ (P > 0.05) compared with CON. In contrast, AF-hens had lower Ca and P levels, but a higher ALP activity than CON (P < 0.01). The AF hens had higher uterine fluid Ca than MF and NF hens (P < 0.05). Compared to CON, the expression level of CaBP-D28K was increased in the shell gland mucosa of MF-hens. Also, MF-, NF-, and AF-hens had higher Osteopontin (OPN) expression level (P < 0.05), whereas NF had a higher expression of OC-116 (P < 0.01). In conclusion, the results indicated that feeding in the afternoon changed the pattern of feed consumption and exerted a positive influence on eggshell thickness.

Sodium humate alters the intestinal microbiome, short-chain fatty acids, eggshell ultrastructure, and egg performance of old laying hens

This study investigated the effect of sodium humate supplementation on changes in the intestinal microbiome, intestinal short-chain fatty acids production, and trace element absorption in older laying hens, with consequent effects on egg performance and shell quality. We used the same hens as their own control; a total of 720 laying hens aged 422 days were randomly divided into three replicates, with the CON group fed a commercial diet at 422–441 days of age and the HANa group fed a commercial diet supplemented with 0.05% sodium humate at 442–461 days of age. Compared with the CON group, in the HANa group, Bacteroidetes and Actinobacteria were significantly increased, whereas, Firmicutes was significantly decreased. Further, Veillonella, Enterococcus, Lactobacillus, and Turricibacter significantly decreased, and Peptoniphilus, Helcococcus, GW-34, Psychrobacter, Anaerococcus, Corynebacterium, Facklamia, Trichococcus, Gallicola, Clostridium, and Oscillospira were significantly increased. The results showed that sodium humate significantly altered the alpha and beta diversity and changed the structure of the intestinal microbiome. Acetic acid, isovaleric acid, and isobutyric acid, among short-chain fatty acids were significantly increased in the HANa group, whereas trace elements such as Mn, Zn, and Fe were significantly reduced. The eggshell strength and ultrastructure were significantly altered. In this study, sodium humate was found to alter the intestinal microbiome structure of aged hens, change the production of short-chain fatty acids, and promote the absorption of trace elements to keep aged hens from experiencing a decrease in egg production performance.

Interactive effect of dietary levels of calcium and 25-hydroxy vitamin D3 on the performance, serum biochemical concentration and digestibility of laying hens from 61 to 70 weeks of age

Objective

The present research was conducted to evaluate the interactive effect of dietary concentration of calcium (Ca) and 25-hydroxy vitamin D3 (25OHD3) on the performance, blood composition and digestibility of laying hens.

Methods

A total of 540 Hy-line brown laying hens aged 61 to 70 weeks were randomly allotted in a 3×3 factorial arrangement, consisting of three levels of 25OHD3 (0, 25, and 50 μg/kg) and three levels of Ca (3.5%, 4.0%, and 4.5%). All diets had basal concentration of 3,000 IU/kg of vitamin D3 including the 2,800 kcal/kg of metabolic energy and 16% of crude protein.

Results

The results showed that interactive effect (p<0.05) between Ca and 25OHD3 was such that dietary 25OHD3 linearly increased interleukin-6 at all levels of Ca inclusion. Interaction (p<0.05) occurred with the highest parathyroid hormone in laying hens that received dietary concentration of Ca (3.5%) with 25OHD3 (50 μg/kg), and Ca (4.0%) with 25OHD3 (50 μg/kg). Egg production and egg weight significantly (p<0.05) increased in the 4.5% Ca group compared to the 3.5% to 4.0% Ca groups. Egg shell thickness and tibia bone length also increased (p<0.05) in groups fed a high-Ca diet (4.0% to 4.5%). Phosphorus digestibility significantly (p<0.05) increased along with dietary Ca level. Among the tested 25OHD3 groups, higher (p<0.05) egg production and tibia thickness were present in hens fed 50 μg/kg of 25OHD3. Furthermore, Ca digestibility serum Ca and 25OHD3 were significantly increased in group offered 50 μg/kg of 25OHD3.

Conclusion

The results gathered in this study indicate that dietary concentrations of 4.0% to 4.5% Ca and 50 μg/kg 25OHD3 improve the performance of hens from 61 to 70 weeks of age.

Effect of Dietary Mineral Content and Phytase Dose on Nutrient Utilization, Performance, Egg Traits and Bone Mineralization in Laying Hens from 22 to 31 Weeks of Age

Simple Summary

The aim of this work was to elucidate how the dietary inclusion of phytase, at a normal dose and overdosed, could affect the utilization of nutrients and performance in young laying hens. When a diet deficient in Ca and P was applied, the dietary inclusion of phytase at low doses (500 FTU/kg) led to an improvement in the digestive efficiency of P in the first weeks after introduction. However, when these deficient diets were maintained in the long term, laying hens improved their digestive utilization of both Ca and P, a higher dose of phytase (1000 FTU/kg) being required to achieve greater P availability. This overdosage also provided additional extraphosphoric advantages, slightly improving access to other nutrients and the feed conversion rate of the hens.

Abstract

A total of 192 laying hens were used to evaluate the effect of dietary mineral content and phytase dose on nutrient utilization, egg production and quality and bone mineralization of young laying hens. Four dietary treatments were studied: PC, positive control with no added phytase, 4.07% Ca and 0.61% P; NC, negative control with no added phytase, 2.97% Ca and 0.37% P; and P500 and P1000, where NC diet was supplemented with phytase at 500 and 1000 FTU/kg, respectively. Hens’ performance and egg traits were controlled from 22 to 31 weeks of age. Coefficients of total tract apparent digestibility (CTTAD) of nutrients were determined at 25 and 31 weeks of age. Apparent ileal digestibility (AID) and blood content of Ca and P, as well as bone traits, were determined at 31 weeks of age. Ca and P retention was higher in birds on PC diet at 25 weeks, but not at 31 weeks of age compared to those on NC diet (p < 0.05). P1000 birds had the highest CTTAD values for dry and organic matter at both ages (p < 0.001). CTTAD of Ca was significantly higher in P1000 diet than in NC diet at 31 weeks of age (p < 0.001). Birds fed with P500 diet at 25 weeks of age and P1000 at 31 weeks of age showed higher CTTAD and retention of P, but lower excretion of P than those fed NC diet (p < 0.05). Phytase inclusion linearly increased AID of dry matter and P (p < 0.001). P500 hens fed had the greatest body weight at the end of the trial (p < 0.05) and P1000 birds had the best feed conversion ratio (p < 0.05). Fowl fed a PC diet produced eggs with higher shell thickness and yolk color than those fed on NC diet (p < 0.05). Phytase inclusion linearly increased the yolk color (p < 0.05). Tibia of laying hens fed with PC had significantly higher ash content than those on NC diet (p < 0.05), and birds fed with P1000 presented intermediate values. It can be concluded that it would be advisable to increase the dose of phytase in the feed of laying hens to obtain long-term benefits.

Effect of inorganic phosphate supplementation on egg production in Hy-Line Brown layers fed 2000 FTU/kg phytase

Phytase has long been used to decrease the inorganic phosphorus (Pi) input in poultry diet. The current study was conducted to investigate the effects of Pi supplementation on laying performance, egg quality and phosphate-calcium metabolism in Hy-Line Brown laying hens fed phytase. Layers (n = 504, 29 weeks old) were randomly assigned to seven treatments with six replicates of 12 birds. The corn-soybean meal-based diet contained 0.12% non-phytate phosphorus (nPP), 3.8% calcium, 2415 IU/kg vitamin D3 and 2000 FTU/kg phytase. Inorganic phosphorus (in the form of mono-dicalcium phosphate) was added into the basal diet to construct seven experimental diets; the final dietary nPP levels were 0.12%, 0.17%, 0.22%, 0.27%, 0.32%, 0.37% and 0.42%. The feeding trial lasted 12 weeks (hens from 29 to 40 weeks of age). Laying performance (housed laying rate, egg weight, egg mass, daily feed intake and feed conversion ratio) was weekly calculated. Egg quality (egg shape index, shell strength, shell thickness, albumen height, yolk colour and Haugh units), serum parameters (calcium, phosphorus, parathyroid hormone, calcitonin and 1,25-dihydroxyvitamin D), tibia quality (breaking strength, and calcium, phosphorus and ash contents), intestinal gene expression (type IIb sodium-dependent phosphate cotransporter, NaPi-IIb) and phosphorus excretion were determined at the end of the trial. No differences were observed on laying performance, egg quality, serum parameters and tibia quality. Hens fed 0.17% nPP had increased (P < 0.01) duodenum NaPi-IIb expression compared to all other treatments. Phosphorus excretion linearly increased with an increase in dietary nPP (phosphorus excretion = 1.7916 × nPP + 0.2157; R2 = 0.9609, P = 0.001). In conclusion, corn-soybean meal-based diets containing 0.12% nPP, 3.8% calcium, 2415 IU/kg vitamin D3 and 2000 FTU/kg phytase would meet the requirements for egg production in Hy-Line Brown laying hens (29 to 40 weeks of age).

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.

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.

Effects of dietary probiotic inclusion on performance, eggshell quality, cecal microflora composition, and tibia traits of laying hens in the late phase of production

Ninety-six White laying hens (64 weeks old) were used to investigate the effect of dietary inclusion of Bacillus subtilis on performance and eggshell quality. Hens were randomly distributed into three treatment groups and fed basal diet (control), basal diet plus 0.5 g/kg B. subtilis (Probiotic-0.5), or basal diet plus 1 g/kg B. subtilis (Probiotic-1) for 10 weeks. Probiotic-1 group exhibited the maximum (P<0.05) increase in egg production, egg weight, egg mass, eggshell weight, and eggshell thickness, compared with Probiotic-0.5 and the control groups. During the last week of the study, eggshell densities were 94.9, 88.7, and 65.6 mg/cm(2) in Probiotic-1, Probiotic-0.5, and the control group, respectively. The average unmarketable eggs were 1.3 %, 2.2 %, and 6.4 % in Probiotic-1, Probiotic-0.5, and the control group, respectively. Tibia weight, density, and ash content increased significantly. The average time required by B. subtilis to establish a significant effect was 3 weeks for Probiotic-1and 6 weeks for Probiotic-5. B. subtilis improved gut microflora balance, which has the potential to improve gut health and absorption efficiency. It should be possible to improve egg performance and eggshell quality of aged laying hens by dietary inclusion of B. subtilis, which will be of importance for farmers.

Minimum Phosphorus Requirement of One-Cycle and Two-Cycle (Molted) Hens

In experiment 1 (one cycle), hens were fed diets containing 0.10, 0.115, 0.125, 0.135, 0.15, or 0.45% available P (AP) from 40 to 56 wk of age, with the last diet being a positive control. Egg production, egg mass, and BW were reduced (P < 0.05) by all lower AP levels except 0.15% AP when compared with the 0.45% AP treatment. In the second experiment (two cycles with a molt), hens were initially fed diets containing 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, or 0.45% AP from 21 to 63 wk of age. Diets containing 0.10, 0.12, and 0.14% AP were terminated at 35, 39, and 50 wk, respectively, due to low egg production and increased mortality. Hens fed 0.16% AP also had significantly lower production performance than hens fed 0.45% AP during the first cycle. Hens on the 0.16 to 0.45% AP treatments were induced molted at 64 wk of age by 10 d of feed removal. The hens were then returned to the same AP layer diet they had been fed from 21 to 63 wk. For the 68 to 108 wk postmolt second-cycle period, hens fed the 0.16 to 0.20% AP diets (166 to 209 mg/d) had significantly lower egg production, egg mass, and feed efficiency than hens fed 0.45% AP. The results of our study indicated that first-cycle hens required approximately 0.18% AP or 198 mg AP/hen per day, and molted hens in their second cycle had a requirement that was greater than 0.20% AP or 209 mg AP/hen per day.

End-of-Cycle Bone Quality in White- and Brown-Egg Laying Hens

Broken and weak bones of laying hens are major welfare concerns in the table egg industry. Bone quality at the end of lay of brown- (Shaver 579) and white-(Shaver 2000) egg strains were compared. Prior to the start of the experiment, the hens had been housed in laying hen cages (2/cage). At 423 d of age (60 wk + 3 d), 24 hens of each strain were selected and individually caged, and egg production records were kept until 462 d of age (the end of 65 wk) for a total of 39 d. Egg quality analysis was undertaken during wk 65 of age. Hens were killed at 66 wk of age (463 d), and carcass and reproductive morphology traits were measured. Femur and humerus mineral density were measured using quantitative computed tomography, and breaking strength was measured by an Instron Materials Tester. The white-egg strain produced 3.7% more marketable eggs during the experiment due to a 0.3 d shorter mean pause length in egg production. Eggs from the brown strain were 3.4% heavier, had 4.0% more eggshell, and had a higher specific gravity than the white strain eggs (1.077 and 1.072, respectively). Final BW was 330 g greater in the brown-egg strain. Total bone density of the femur was not different between the 2 strains but was greater in the humerus of the brown-egg layers. Total femur and humerus bone areas were greater in the brown strain than the white-egg strain. Bone breaking strengths of the brown-egg strain were greater by 22% (femur) and 18% (humerus) than in the white-egg strain hens. These results indicate that this brown-egg strain may be more resistant to weak and broken bones at the end of production than the white-egg strain.

Intestinal and eggshell calbindin, and bone ash of laying hens as influenced by age and molting

A series of trials was conducted in order to study the effects of age and molt on intestinal and eggshell gland (ESG) calbindin, and on bone ash. For this purpose an ELISA for chicken calbindin was developed. Age did not significantly affect duodenal or ESG calbindin. Bone ash increased (but not significantly in this study) from 8 to 16 months of age. During molt induction, egg laying was arrested, duodenal and ESG calbindin almost completely disappeared and ovary mass, plasma estradiol and total calcium (Ca) decreased markedly, whereas bone ash and body mass (BW) decreased moderately. During the non-laying period that followed the feed withdrawal period, duodenal and ESG calbindin remained low, whereas plasma estradiol and other estrogen-dependent variables, such as plasma total Ca and bone ash, increased slightly. At the onset of egg production following molting, duodenal and ESG calbindin levels were similar to pre molt level. Bone ash was higher than at the pre molt period. Body mass, small yellow follicles, ovary and oviduct mass and plasma estradiol were lower than their values prior to molt induction. Bone ash contents in the molted hens at the ages of 583 and 820 days were similar to or even slightly higher than those in the non-molted hens, whereas duodenal and ESG calbindin were not significantly different. These results suggest that the improvement of shell quality in the molted birds does not involve mechanisms associated with calbindin synthesis.