This study was conducted to investigate effects of dynamic feeding low and high methionine (MET) diets on performance, egg quality traits, and serum metabolites in laying hens. A total of 180 laying hens (Brown Hy-line, 41 wk old) were allocated into 3 equal groups with 6 replicates each. The average egg production (EP) of each group was around 87% during one-week statistics before the formal experiment (P = 0.989). The control group (CON) received the control diet (contained 0.30% MET) at both 07:30 h and 15:30 hours. The low-high group (LH) received a low MET diet (containing 0.27% MET) at 07:30 h and high MET diet (containing 0.33% MET) at 15:30 hours. The high-low group (HL) received a high MET diet at 07:30 h and low MET diet at 15:30 hours. After 10 wk, blood samples were collected at 4-hour intervals in a daily cycle initially starting at 07:30 h before feeding. Results showed that the MET intake of a d was not influenced by the treatments (P > 0.05), respectively. The EP of the LH and HL group increased by 2.28 and 2.45% when compared with the CON group (P > 0.05). The hens in the LH group had a lower albumen ratio and thicker eggshell thickness than both CON and HL groups. Egg yolk ratio of the LH group was higher than the HL group (P < 0.05). The serum total cholesterol (TC), total triglyceride (TG), total protein (TP), and calcium (Ca) of the LH group was significantly lower at 07:30 h than the CON and HL groups, and the serum TG of the HL group was lower at 07:30 h than the CON group (P < 0.05). Meanwhile, the LH group also had the lowest value of serum TP at 23:30 h and 03:30 h (P < 0.05). These results demonstrated that dynamic feeding low and high MET diets might alter the circadian variation of serum TC, TG, TP, and Ca, which is consistent with the change of component ratio of egg albumen and yolk and eggshell thickness.

To ascertain an appropriate level of isoleucine for LSL-LITE layers (23- to 30-week-old), diets containing total isoleucine concentrations (levels) of 0.66 (Control), 0.69, 0.72, 0.75, 0.78, 0.81, and 0.84% were fed as 7 treatments (2730 kcal/kg metabolizable energy) x 7 replicates x 10 birds per replicate. Significance for performance, egg quality, serum biochemistry, and ileal digestibility of protein was determined at P ≤ 0.05. Level, week, and level*week (L*W) were significant for production, egg mass, and feed intake. Level and week were significant for FCR. Week was significant for weight gain. Level was significant for egg weight, specific gravity, and shell thickness; week was also significant for these external egg parameters as well as shape index and proportional shell thickness. L*W was significant for all except shape index. For internal egg measurements, level was significant for proportional yolk, proportional albumen, yolk index, and yolk:albumen. Week was significant for internal egg parameters while L*W significantly affected Haugh unit, proportional albumen weight, yolk index, albumen index, and yolk color. Level was significant for globulin and glucose in serum. Isoleucine at 0.72%, 0.81%, and 0.84% produced the lowest FCR, an important standard in the poultry industry. Considering the low FCR of 1.45 and cost for inclusion as a dietary ingredient, 0.72% isoleucine was chosen for further studies with varying quantities of other branched chain amino acids in diets for young laying hens.

Dietary sodium (Na) levels were related to the content of the eggshell matrix. We therefore speculated that dietary Na supplementation as sodium bicarbonate (NaHCO) or sodium sulfate (NaSO) may improve eggshell quality. Additionally, dietary NaHCO or NaSO supplementation may further affect eggshell quality in different ways due to differences in anions. This study investigated and compared the effects of dietary Na supplementation in either NaHCO or NaSO form on laying performance, eggshell quality, ultrastructure and components in laying hens. A total of 576 29-week-old Hy-Line Brown laying hens were randomly allocated to 8 dietary treatments that were fed a Na-deficient basal diet (0.07% Na, 0.15% Cl) supplemented with NaSO or NaHCO at 0.08, 0.18, 0.23 or 0.33% Na for 12 weeks. No differences were observed in laying production performance with dietary Na supplementation. Dietary Na supplementation resulted in quadratic increases of eggshell breaking strength in both NaSO and NaHCO added groups (P < 0.05), and NaSO-fed groups had a quadratic increase in the eggshell ratio at week 12 (P < 0.05). Compared with supplementing 0.08% Na, dietary supplementation of 0.23% Na increased the effective thickness (P < 0.05) in both NaSO and NaHCO added groups, but decreased the thickness and knob width of the mammillary layer (P < 0.05). A linear increase on the calcium content of the shell was only observed with Na supplementation from NaHCO (P < 0.05). No differences were observed in Na contents of the shell with dietary Na supplemented by both sources. Dietary Na addition had a quadratic increase on uronic acid contents of shell membrane in NaHCO-fed groups (P < 0.05). Moreover, the sulfated glycosaminoglycan (GAG) contents of shell membranes increased linearly with dietary Na supplementation (P < 0.05). Dietary supplementation of 0.23% Na from NaSO increased the sulfated GAG contents of calcified eggshell (P < 0.05). Additionally, compared with NaHCO-fed groups, NaSO-fed groups had higher eggshell breaking strength, thickness, eggshell weight ratio, effective thickness and the sulfated GAG contents of calcified eggshell at week 12. Overall, dietary supplementation of NaHCO or NaSO could increase eggshell breaking strength, which may be related to increased sulfated GAG contents in eggshell membranes and improved ultrastructure. Higher eggshell breaking strength, thickness and eggshell ratio could be obtained when the diet was supplemented with 0.23% Na from NaSO.

1. A significant linear increase in egg-shell defects from 60-week-old laying hens, and corresponding significant linear decreases in various egg-shell-quality measurements, were observed in response to increasing concentrations of sodium chloride in the drinking water, to the maximum concentration of 600 mg/l used in the present study. 2. The incidence of damaged egg shells was increased 3-fold by including NaCl in the drinking water at a concentration of 600 mg/l. 3. Shell defects declined when birds were placed on normal water for 5 weeks but were still 1.4- to 2.1-fold greater than control values. 4. After an induced rest from lay on normal water, shell defects were still 1.3- to 3.2-fold greater in birds which had previously received the NaCl in the drinking water. 5. The increased incidence of shell damage was not related to decreased food intake or increased egg weight or production.

Sodium sulfate (NaSO) is a readily available chlorine-free source of sodium, which could be used to reduce sodium chloride to maintain the ratio between chlorine and sodium in poultry diets. Dietary supplementation with excessive levels of NaSO might be detrimental to bird's health and performance. A subchronic study was carried out to investigate the potential adverse effects of an accidental oversupply of NaSO in the diets of laying hens. Four hundred and fifty 21-week-old Hy-Line White layers were randomly assigned to 5 treatments with 6 replicates. The birds were fed diets supplemented with 0 (control), 0.3%, 0.6%, 1.5%, and 3.0% NaSO for 8 weeks. Laying performance, egg quality parameters, clinical blood parameters, histopathology, intestinal barrier functions, and intestinal microflora composition were measured. No clinical signs of intoxication or mortality were observed during the experimental period. The results of this study showed that the optimal levels of NaSO (0.3% to 0.6%) significantly improved the laying rates, average daily egg mass, and eggshell quality of hens compared to the control ( < 0.05). However, 3.0% NaSO produced negative effects on laying performance, eggshell quality, blood biochemistry, and particularly on liver and kidney pathology, and intestinal morphology and barrier functions compared with the controls. Although minor changes were observed in clinical blood parameters of hens receiving 1.5% NaSO, these were not considered to be of toxicological significance due to the absence of any organ pathological changes in hens. In conclusion, our results indicated that a NaSO concentration of 1.5% was non-deleterious to laying hens after a daily administration for 56 d, namely that dietary supplementation of up to 5 times the maximum recommended dose is safely tolerated by laying hens.

1. Supplementing the drinking water of 50-week-old laying hens with sodium chloride (NaCl) concentrations between 0.5 and 2 g/l for 7 weeks significantly increased the incidence of egg shell defects and significantly decreased egg shell quality. Dietary NaCl concentrations between 0 and 2 g/kg had little effect on this response. 2. At similar total NaCl intakes egg shell defects were much greater when the NaCl was obtained from the drinking water rather than from the diet. 3. Hens producing eggs with defective shells as a result of receiving saline drinking water failed to recover the ability to lay eggs with good shells after 8 weeks on normal water. 4. The increased incidence of shell damage was not related to decreased food intake or increased egg weight or production.

Three experiments were conducted to determine the effect of sodium aluminosilicate (SAS), oyster shell (OS), and their combinations on production performance, eggshell quality, and acid-base balance. Experiments 1 and 2 were conducted during summer and Experiment 3 in winter. In Experiment 1, the effect of two levels of SAS (0 and .75%) and two levels of OS (0 and 50% substitution for pulverized limestone) was studied. In Experiment 2, the effect of SAS (.75%) with or without Na adjustment was investigated. When Na was adjusted, various sources of chloride were used to maintain an adequate level of this mineral. Calcium and available P were maintained at a constant 3.5 and .4%, respectively in Experiments 1 and 2. In Experiment 3, the levels of SAS and OS were similar to those of Experiment 1, but dietary Ca was either 2.8 or 3.5%. Egg production performance was not influenced by dietary treatments in Experiments 1 and 2 (P greater than .05). Egg production, but not egg mass, was reduced due to SAS in Experiment 3 (P less than .05). Dropping moisture increased when SAS was used in the diets with or without Na correction. Shell quality increased (P less than .05) due to SAS in the summer (Experiments 1 and 2) but not in the winter (Experiment 3). The shell quality response due to SAS was independent of Na correction or the source of dietary chloride. The OS increased shell quality in both summer and winter (P less than .05). Combinations of SAS and OS did not have an additive effect on shell quality (P greater than .05). Blood acid-base balance, plasma Ca and P, bone ash, bone Ca, and Ca retention were not influenced by dietary treatments. The results suggest that elevated environmental temperatures may be required in order for SAS to show its optimum effect on shell quality.

Hubbard ISA IsaBrown pullets were purchased from a commercial supplier at 16 wk of age and kept at a constant 18 C or a constant 30 C in temperature-controlled rooms. The purpose of our experiment was to determine the effect of ambient temperature on the eggshell quality responses of laying hens receiving saline drinking water with or without simultaneous supplementation of the diet with ascorbic acid or Zn methionine. Four treatments were investigated: 1) a basal layer diet (C) and local drinking water, 2) diet C and local drinking water containing 2 g NaCl/L, 3) diet C containing 200 mg ascorbic acid/kg and local drinking water containing 2 g NaCl/L, and 4) diet C with 360 mg Zinpro 100 (Zn methionine)/kg and local drinking water containing 2 g NaCl/L. The local drinking water contained <1 mmol Cl/ L. The pullets received a continuous daily photoperiod of 16 h from fluorescent lighting, and production measures were made between 20 and 60 wk of age. Production and eggshell quality were significantly reduced at 30 C compared with 18 C but were not significantly affected by the dietary and water treatments. The results indicated that the IsaBrown hens were relatively insensitive to intakes of NaCl from the drinking water at concentrations of 2 g/L. This lack of sensitivity in eggshell quality contrasts with the majority of published reports, including earlier work with local Australian layer strains. It is suggested that this contrasting sensitivity may relate to the concentration of dietary NaCl used during the selection of layer genotypes.

Two experiments with White Leghorn hens (36 and 49 wk old, respectively) were conducted to examine the effects of varying NaCl concentrations provided through drinking water upon eggshell quality. Experiments were of 6 and 5 wk duration, respectively. Seven replicate pens of five individually caged hens received each water treatment. Treatments were the same in both studies and consisted of low-Na (9 ppm) tap water supplemented with 0, 200, 400, 600, or 800 ppm NaCl. Solutions were prepared weekly. All eggs produced were examined visually for shell defects, and egg weight and specific gravity were determined. In the second experiment, eggs from 2 consecutive d were also broken out each week for Haugh Unit determinations. In both studies, hen-day egg production, daily feed and water intake, egg weight, and body weight change over the experimental period were not influenced by any level of waterborne NaCl. Haugh Units were also not affected in Experiment 2. In contrast to other literature reports, visually determined shell defects and egg specific gravity were not adversely affected by NaCl supplementation of layer drinking water.

Two experiments were conducted to determine the influence of dietary sodium and chloride on eggshell quality of leghorn hens. In the first, hens were fed for 4 wk diets containing three levels of calcium (2.0, 2.8, and 3.5%) and two levels of chloride (.25 and .86%) in a factorial arrangement of treatments involving four replicates of five hens/treatment. Neither chloride nor calcium significantly affected hen-day egg production or egg weight (P greater than .05); however, chloride decreased feed consumption and calcium increased body weight gain (P less than .05). Interactions of calcium and chloride were significant for eggshell strength (P less than .06) and eggshell thickness (P less than .05). Chloride decreased these measures of eggshell quality only for hens receiving 2.0% calcium, and calcium improved both measures only for hens receiving .86% chloride. Chloride decreased blood bicarbonate concentration and base excess (P less than .05), but did not affect blood pH and pCO2 (P greater than .05). The effect of dietary sodium and chloride on eggshells of hens receiving 2.0% dietary calcium was determined in a second experiment. Seven diets ranging from .18% sodium and .94% chloride to .76% sodium and .24% chloride were provided for 4 wk to five replicates of five hens/treatment. Dietary sodium and chloride levels did not affect hen-day egg production or egg weight (P greater than .05). Increasing the proportions of sodium relative to chloride decreased food intake but increased eggshell strength and thickness (P less than .01) and increased blood pH (P less than .05), bicarbonate concentration (P less than .01), and base excess (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to evaluate the effect of dietary chloride (Cl) levels on performance, eggshell mechanical quality, and ultrastructure in layers based on the substitution of sodium chloride (NaCl) by sodium sulfate (NaSO). Three hundred sixty Jing Brown laying hens aged 43 wk were randomly divided into 5 groups and fed with corn-soybean meal diets containing 0.06, 0.10, 0.15, 0.20, and 0.25% total Cl inclusion. Every group had 8 replicates of 9 birds each. The feeding trial lasted for 12 wk. The results showed dietary 0.06% Cl due to complete substitution of NaCl by NaSO, depressed performance (P < 0.05) from 45 to 54 wk of age, increased serum creatinine level (P < 0.05), and caused visible renal tubular atrophy. Dietary Cl levels quadratically affected breaking strength, thickness, and weight of eggshell (P < 0.05). Better eggshell quality could be obtained when NaCl was partly replaced by NaSO in laying hen diets maintaining Cl level at 0.10 or 0.15%. Moreover, the eggshell ash content was affected by Cl levels in a quadratic (P < 0.001) manner, with higher values observed in the 0.10 and 0.15% Cl groups (P < 0.05). Besides, the eggshell ultrastructural data showed that the total thickness and effective thickness significantly increased (P < 0.05) and mammillary thickness decreased (P < 0.05) in the group of dietary 0.15% Cl compared with the groups of 0.06 and 0.25% Cl. In conclusion, the complete substitution of dietary NaCl by NaSO may induce Cl deficiency and depress laying performance and eggshell quality. NaSO could partly replace NaCl in diets for laying hens (43-54 wk of age) without adverse effects on performance at the dietary Cl level from 0.10 to 0.25%. Better eggshell quality could be obtained when NaCl was partly replaced by NaSO in laying hen diets maintaining Cl level at ∼0.15%.

This study investigated the effects of dietary chloride (Cl) reduction on laying performance and eggshell quality by substitution of sodium bicarbonate (NaHCO) or sodium sulfate (NaSO) for part of dietary sodium chloride (NaCl), and further explored its mechanism for improving eggshell quality. A total of 360 29-wk-old Hy-line Brown laying hens were randomly allocated to 5 dietary treatments, including a basal diet contained 0.33% NaCl (control group, 0.27% dietary Cl), and 4 experimental diets that contained 0.21% and 0.15% dietary Cl by substituting NaSO or NaHCO for part of NaCl in the basal diet. No significant differences were observed in blood Na, Cl, K and Ca levels and pH value as well as serum creatinine and uric acid contents among 5 treatments (P > 0.05). Dietary Cl reduction increased egg production and ADFI during wk 33 to 36, 37 to 40 and 29 to 40 of age and decreased feed conversion ratio during wk 37 to 40 of age (P < 0.05). The hens fed with diets containing 0.15% Cl increased eggshell breaking strength, thickness and weight ratio in wk 40 of age (P < 0.05). Birds fed with dietary 0.21% and 0.15% Cl exhibited higher effective layer thickness and lower mammillary layer thickness of eggshell than those fed with dietary 0.27% Cl (P < 0.05). Apparent Ca metabolizability of hens was increased with dietary Cl reduction (P < 0.05). Total Ca of eggshell of dietary 0.15% Cl group was higher than that of dietary 0.27% Cl group (P < 0.05). No significant differences in laying performance, eggshell quality and Ca metabolism of layers were observed between NaSO and NaHCO replacement groups (P > 0.05). Overall, dietary Cl reductions could improve laying performance and eggshell quality by substitution of NaHCO or NaSO for part of NaCl, and there were no differences in the improvements between these two substitutes. The improved eggshell quality may be attributed to improved eggshell ultrastructure and increased supply of eggshell CaCO.