Interrelationship Between Phosphorus, Sodium, and Chloride in the Diet of Laying Hens1

Interrelationship Between Phosphorus, Sodium, and Chloride in the Diet of Laying Hens1 O. M. JUNQUEIRA, 2 R. D. MILES, and R. H. HARMS3 Poultry Science Department, University of Florida, Gainesville, Florida 32611 (Received for publication December 16, 1982)

1984 Poultry Science 63:1229-1236 INTRODUCTION Data in the literature as to the phosphorus requirement of laying hens have been conflicting. Lee et al. (1968) reported that the requirement for total phosphorus was between .58 and .81% and recommended .7% total phosphorus in the diet. Paul and Snetsinger (1969) reported reduced egg production with .35% total phosphorus; however, .35 through .80% phosphorus in the diet did not affect specific gravity of eggs. Harms et al. (1965) reported that too much phosphorus in the diet of caged laying hens would depress egg production. Recently, Harms (1982) recommended a daily intake of 650 mg of total phosphorus from 20 to 36 weeks of age and an intake of 450 mg per day after 53 weeks of age.

1 Florida Agricultural Experiment Station Journal Series No. 4197. 2 Present address: UNESP-Jaboticabal-SP-Brazil. 3 To whom correspondence should be addressed.

Choi et al. (1979) concluded that the hen is capable of maintaining a normal blood phosphorus level over a wide range of dietary phosphorus but decreases her serum phosphorus level immediately when fed suboptimal levels of phosphorus. Sodium bicarbonate has been used in an effort to improve eggshell quality. Latif and Quisenberry (1968) observed that the effects of sodium bicarbonate on specific gravity were quite variable. Shell thickness and specific gravity appeared to be improved, but the differences were not significant. Miles and Harms (1982) found that the addition of sodium bicarbonate or increasing the calcium content of the diet resulted in a decrease in plasma phosphorus and an increase in egg specific gravity. Cohen et al. (1972) observed a significant interaction between dietary sodium and chloride as measured by various acid-base parameters in the laying hen. The first experiment in this paper was conducted to determine the effects of feeding

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ABSTRACT Two experiments were conducted with commercial egg production type hens to determine the effects of dietary phosphorus, sodium, and chloride levels as related to levels of plasma calcium and phosphorus, blood acid-base balance, and production characteristics. Sodium and chloride were supplied to the diet as sodium bicarbonate and hydrochloric acid, respectively. In Experiment 1, five treatment groups were fed diets ad libitum containing .2, .6, 1.0, 1.4, and 1.8% total phosphorus. The remaining treatment group was fed a diet containing .4% total phosphorus from 1400 to 2030 hr and 1.4% total phosphorus from 600 to 1100 hr. In Experiment 2, a 3 X 4 factorial arrangement of treatments was used that consisted of three levels of total phosphorus (.2, .6, and 1.4%) and four levels of added sodium (0, .06, .22, and .45%) provided by sodium bicarbonate. Three other treatment groups were fed diets containing .36% supplemental chloride supplied by hydrochloric acid and either .2, .6, or 1.4% total phosphorus. Egg production was decreased in hens fed diets containing 1.8% total phosphorus. Egg specific gravity was decreased by both low and high phosphorus levels. Hens fed .4% total phosphorus in the afternoon produced eggs with higher specific gravity as compared with hens fed 1.4% total phosphorus during the entire experiment. At 1.4% dietary phosphorus, a significant increase in specific gravity was observed when .2 or .8% sodium bicarbonate was added to the diet. Increasing dietary phosphorus resulted in elevated plasma phosphorus and calcium concentration. Plasma phosphorus of hens fed .2 through 1.8% total phosphorus declined slowly from oviposition until 6 hr after oviposition and then reached a peak at 21 hr after oviposition. Blood pH did not change by increasing the dietary phosphorus level or by adding sodium bicarbonate and chloride to the diet. Base-excess (non-HCO,), bicarbonate, and total C 0 2 were found to be inversely related to the dietary phosphorus levels. (Key words: laying hens, phosphorus, sodium, chloride)

JUNQUEIRA ET AL.

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MATERIALS AND METHODS

Experiment 1. Three-hundred, 62-week-old Hy-Line W-36 laying hens were randomly assigned to six treatments, consisting of five replicates of 10 birds each housed in individual wire cages. Five treatment groups were fed diets ad libitum containing .2, .6, 1.0, 1.4, and 1.8% total phosphorus. The remaining treatment group was fed a diet containing .4% total phosphorus from 1400 to 2030 hr and 1.4% total phosphorus from 600 to 1100 hr. All diets contained 15.6% crude protein, 2871 kcal ME/kg, and 3.4% calcium (Table 1) and were formulated according to the specifications of Harms (1979a). Egg production and feed consumption were recorded daily and at 2-week intervals, respectively. Specific gravity and weight of all eggs laid on every 7th day were determined during the 6-week experimental period. Blood samples were obtained from 10 to 12 hens per treatment. Hens were bled at oviposi-

TABLE 1. Composition of the experimental diets (Experiment 1) % Total phosphorus Ingredients Degerminated corn Yellow corn Soybean meal (48.5% protein) Limestone Dicalcium phosphate (18% Ca, 21% P) Microingredients1 Iodized salt DL-Methionine Sand Animal fat

.2

1.0

.6

1.4

1.8

.4

70.00 63.75 20.50 8.55

19.80 8.80

63.75 20.50 7.95 1.51

63.75 20.50 6.76 3.67

63.75 20.50 5.57 5.83

63.75 20.50 4.37 8.00

.50 .40 .10

.50 .40 .10

.50 .40 .10

1.94 2.38

.50 .40 .10 .00

.30

2.91 2.38

.50 .40 .10 .97

2.38

2.38

3.39 2.38

15.60 2871 3.40

15.60 2871 3.40

15.60 2871 3.40

15.60 2871 3.40

15.60 2871 3.40

15.60 2871 3.40

.43 .50 .40 .10

Calculated analysis Crude protein, % Metabolizable energy, kcal/kg Calcium, %

1 Supplied per kilogram of feed: 6000 IU vitamin A; 2200 ICU vitamin D 3 ; 2.2 mg menadione dimethylpyrimidinol bisulfite; 4.4 mg riboflavin, 13.2 mg pantothenic acid; 39.6 mg niacin; 499 mg choline chloride; 22 Mg vitamin B 1 2 ; 125 mg ethoxyquin; 50 mg manganese; 50 mg iron; 6 mg copper; .198 mg cobalt; 1.1 mg iodine; 35 mgzinc.

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tion and 6 and 21 hr following oviposition. The blood samples collected from hens at 6 and 21 hr following oviposition were analyzed only if hens laid the following day. After being collected in a heparinized 10-ml syringe with a 20-gauge needle attached, blood samples were centrifuged, and 1 ml of plasma was deproteinized with 4 ml of a 10% trichloroacetic acid solution. Total inorganic phosphorus was determined using a Perkin-Elmer UV-vis spectrophotometer, Model 139, by the method of Harris and Popat (1954). Plasma calcium was determined using a Perkin-Elmer Atomic Absorption Spectrophotometer, Model 306, by the method of Slavin (1964). Experiment 2. Six hundred 41-week-old Hy-Line W-36 laying hens were randomly assigned to 15 treatment groups, each consisting of four replicates of 10 birds each. Twelve treatments were studied in a 3 X 4 factorial arrangement, which consisted of three levels of total phosphorus (.2, .6, and 1.4%) and four levels of added sodium (0, .06, .22, and .45%) provided by sodium bicarbonate. The three remaining treatment groups were fed diets containing .36% supplemental chloride supplied by hydrochloric acid and either .2, .6, or 1.4% total phosphorus. The hens were maintained in individual wire cages and fed the experimental diets ad libitum for 10 weeks. Water was furnished to the hens by a continual flow-

various levels of dietary phosphorus on the performance and blood phosphorus level of laying hens. The second experiment was designed to investigate the interrelationship between sodium, chloride, and phosphorus in the laying hen with regard to performance and blood parameters.

PHOSPHORUS, SODIUM, CHLORIDE IN HEN DIETS through system for 15 min every 90 min. Natural light was supplemented with artificial light to furnish 16 hr of continuous light each day. The corn-soybean meal basal diets (Table 2) were calculated to contain 16.5% crude protein, 2824 kcal ME/kg, 3.73% calcium, and .03% NaCl. Egg production was recorded daily and feed consumption was recorded at 2-week intervals. Every 7th day of the experimental period all eggs were collected and individually weighed and their specific gravity determined. In the 6th week of the experiment, blood samples were collected as described in Experiment 1. Samples were collected only from hens fed the high and low supplemental sodium levels and chloride at the .2 and 1.4% phosphorus level. Immediately following collection, blood samples were analyzed for base excess, pH, bicarbonate, and total CO2 content using an automated Blood Gas Analyser (IL Model 813 Instrument Laboratory Inc., Lexington, MA) calibrated for chicken blood. Bicarbonate content of the blood was calculated from the Henderson-Hasselbalch equation, with a pk = 6.10 and the a, the solubility constant for CO2 in plasma = .0306 m/W/mmHg. Plasma inorganic

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phosphorus and calcium were determined by the methods and procedures as described in Experiment 1. Data from both experiments were analyzed using the analysis of variance and significant differences between treatments determined by Duncan's multiple range test according to Snedecor (1956). RESULTS AND DISCUSSION

TABLE 2. Composition of the basal diet (Experiment 2) % Total phosphorus Ingredients Degerminated corn Yellow corn Soybean meal (48.5% protein) Limestone Dicalcium phosphate (18% Ca, 21% P) Microingredients1 Iodized salt DL-Methionine Animal fat Variables2

.20

.60

1.40

60.51 23.40 9.63

60.51 23.03 8.77 1.54

58.12 23.40 6.39 5.86

.55 .45 .13

.55 .45 .13

.55 .45 .13

2.40 2.93

2.14 2.88

2.98 2.12

16.50 2824 3.73

16.50 2824 3.73

16.50 2824 3.73

Calculated analysis Crude protein, % Metabolizable energy, kcal/kg Calcium, %

'Supplied per kilogram of feed: 6000 IU vitamin A; 2200 ICU vitamin D 3 ; 2.2 mg menadione dimethylpyrimidinol bisulfite; 4.4 mg riboflavin; 13.2 mg pantothenic acid; 39.6 mg niacin; 499 mg choline; 22 fig vitamin B 1 2 ; 125 mg ethoxyquin; 50 mg manganese; 50 mg iron; 6 mg copper; .198 mg cobalt; 1.1 mg iodine; 35 mg zinc. 2

Supplied variable amounts of sodium bicarbonate, hydrochloric acid, and white builder's sand.

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Experiment 1. Egg production was reduced (P<.05) w h e n h e n s were ted diets containing .2% total phosphorus (Table 3) but was not reduced by feeding diets containing levels of .6, 1.0, and 1.4% total phosphorus. However, 1.8% total dietary phosphorus reduced (P<.05) egg production when compared with that observed at .6% phosphorus. Feeding lower levels of phosphorus in the afternoon did not affect egg production. These results were similar to those found by Singsen et al. (1962), who reported that hens maintained on wire required more than .40%, but not more than .60% total phosphorus, for satisfactory egg production. Harms et al. (1965) also reported that 1.15% total phosphorus depressed egg production. Feed intake was reduced (P«.05) by feeding .2% phosphorus. These data do not agree with

JUNQUEIRA ET AL.

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TABLE 3. Egg production, feed conversion, feed intake, egg weights, and egg specific gravity when hens were fed diets with various levels of phosphorus, Experiment 1 Total dietary phosphorus

c

53.l 72.0 a 69.3ab 69.2ab 67.lb 69.5ab

Feed intake

Feed conversion

Egg weight

Specific gravity

(g) 74.1 b 97.2 a 97.2 a 97.4 a 101.0 a 95.0 a

(kg/doz)

(g) 58.3 b 62.6 a 61.7 a 62.2 a 61.4 a 62.6 a

1.0751 d 1.0806 ab 1.0787 b c 1.077icd 1.0752 d 1.0817 a

1.68 a 1.62 a 1.69 a 1.69a 1.81 a 1.69 a

' ' ' 'Means within columns with different letters are significantly different (P«.05). 1

Fed .4% total phosphorus from 1400 to 2030 hr and 1.4% total phosphorus from 600 to 1100 hr.

those of Owings et al. (1977) and Guenter (1980), who reported that feed intake was not affected by dietary phosphorus level. However, no significant difference in feed intake was observed in hens fed diets containing from .6 to 1.8% phosphorus. Feed required to produce a dozen eggs did not differ between treatments. Feed intake was shown to be related to level of egg production in this study, even at the level of .2% phosphorus. Similar results were also found by Walter and Aitken (1962), Crowley, et al. (1963), and Reichmann and Connor (1977). Hens fed .2% phosphorus laid significantly lighter eggs. However, no difference was observed when hens were fed higher phosphorus levels in the diet. Egg specific gravity increased (P<.05) when phosphorus increased from .2 to .6% and then decreased in a linear fashion (r = .96) up to 1.8% phosphorus. Data reported by several investigators have shown that when high

phosphorus levels are fed, eggshell quality is decreased (Hunt and Chancey, 1970; Damron et al, 1974; Bletner and McGhee, 1975; Harms and Miles, 1977; Reichmann and Connor, 1977; El Boushy, 1979; Ousterhout, 1980). The excessive intake of phosphorus has been shown to influence the precipitation of calcium carBohate_under physiological ^onditjons (Smith et al, 1954). Also, Bachra et al. (1963) showed that calcium carbonate precipitation was prevented by the presence of phosphate ions by the formation of calcium phosphate. The level of .4% phosphorus fed during the afternoon resulted in a significant improvement in egg shell quality. This is in agreement with reports of Roland and Harms (1976). These data indicated that dietary phosphorus level has an influence on eggshell quality when the hen is forming the egg shell. Plasma phosphorus at 6 hr after oviposition and at oviposition did not differ significantly, except for hens fed .2% phosphorus (Table 4).

TABLE 4. Plasma inorganic phosphorus (mg/100 ml) of laying hens fed different levels of dietary phosphorus, Experiment 1 Dietary phosphorus (%) Time

.2

.6

1.0

1.4

1.8

.4+ 1.41

Oviposition 6 hr after oviposition 21 hr after oviposition

2.05 b .89 c 3.26 a

4.72 b 3.69 b 6.10 a

5.36b 5.31 b 7.08 a

5.80 b 5.45 b 7.00 a

6.45 b 6.15 b 8.26 a

4.20 b 3.54° 5.86 a

' ' Means within columns with different letters are significantly different (P<.05). 1

Fed .4% total phosphorus from 1400 to 2030 hr and 1.4% total phosphorus from 600 to 1100 hr.

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.2 .6 1.0 1.4 1.8 .4-1.4'

Egg production

PHOSPHORUS, SODIUM, CHLORIDE IN HEN DIETS

phosphorus (Table 5). This finding is in agreement with the results of Experiment 1 and with Singsenef al. (1962). Sodium levels used in this study did not affect egg production except when a level of .45% was fed with .2% total phosphorus (Table 5). Howes (1966) found that sodium bicarbonate significantly increased egg production; however, contrary to this report, Cox and Balloun (1968) observed a lower rate of egg production caused by feeding sodium bicarbonate. Daily feed intake increased as total dietary phosphorus was increased (Table 5). Harms et al. (1965) reported no difference in feed consumption when hens were fed diets containing between .68 and 1.68% total phosphorus. However, Singsen et al. (1962) reported a depression in feed intake when laying hens were

TABLE 5. Performance of hens fed different levels of sodium and chloride at three phosphorus levels, Experiment 2 Dietary phosphorus

Added Na or CI

production

Feed intake

Feed efficiency

weight

(%)

(g)

(kg/do z)

(g)

Egg

Source

\'o) .20 .20 .20 .20 .20

.00 .06 .22 .45 .36

NaHC0 3 NaHC0 3 NaHC0 3 NaHC0 3

.60 .60 .60 .60 .60

.00 .06 .22 .45 .36

NaHC0 3 NaHC0 3 NaHC0 3 NaHCO,

1.40 1.40 1.40 1.40 1.40

.00 .06 .22 .45 .36

NaHC0 3 NaHCO, NaHC0 3 NaHCO,

HC1

HC1

HC1

61.3 b 58.0 b c 57.8 b c 49.3 c 58.0 b c

76.6 C 76.9 C 76.5 C 70.1C 71. l c

1.90 a b c 2.15 a 2.01 a 2.31 a 2.13 a

82.4 a 80.7 a 80.5 a 81.5 a 79.8 a

97.8ab 94.6 b 96.9ab 96.2 b 95.9 b

80.2 a 79.0 a 79.0 a 79.0 a 80.3 a

56.9 b 81.0 a 79.6 a

Egg

Specific gravity

58.8 b c 57.7C 59.0 b c

1.0819 f 1.0845 b c d e 1.0846 b c d e 1.0833 ef 1.0829 ef

1.47C 1.46 c 1.47C 1.44c 1.48 c

61.3 a 62.0 a 61.5 a 61.8 a 61.6 a

1.0863 a b 1.0867 a 1.0864 a b 1.0854 a b c 1.0856 a b c

106.0 a 101.8 a b 102.2 a b 101.5 a b 103.lab

1.63 b c 1.63 b c 1.59 bc 1.57 bc 1.58 bc

62.3 a 61.6 a 61.la 61.8 a 60.8 a

1.0834 d e f 1.0853 a b c d 1.085 3 a b c d 1.0837 cd ef 1.0832ef

75.0 C 96.4 b 102.9 a

2.10 a 1.46 b 1.61 b

58.7° 61.7 a 61.7 a

1.0836C 1.0862 a 1.0844 b

1.67a 1.75 a 1.69 a 1.78 a

60.8 a 61.0 a 60.5 a 60.4 a

1.0839 b 1.0855 a 1.0855 a 1.0841 b

58.9 b c 59.3D

Among phosphorus levels1 .20 .60

1.40 Among sodium levels1 .00 .06 .22 .45

74.6 a 72.6 a 72.4 a 70.0 a

93.5 a 91.1bc 91.9ab 89.2 C

3, b c d c f Means within columns within group with different letters are significantly different (P<.05). 1

Does not contain the treatment with supplemental chloride as HC1.

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However, an increase (P<.05) in plasma inorganic phosphorus was observed 21 hr after oviposition in all treatments. These differences indicated that plasma phosphorus increased during eggshell formation. Previous studies have shown that the plasma inorganic phosphorus level of the hen increases after about 12 hr following oviposition (Feinberg et al., 1937; Peterson and Parrish, 1939; Miller et al., 1977; Mongin and Sauveur, 1979). The hyperphosphatemia correlates with the increased rate of shell calcification and medullary bone demineralization during the later stage of shell formation. The increase in plasma phosphorus can also be related to the inability of the kidneys to excrete phosphorus at a rate equal to its liberation from bone (Taylor and Stringer, 1965). Experiment 2. Egg production was depressed (P«.05) when hens were fed .2% dietary

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JUNQUEIRA ET AL.

1982). The level of .45% may have been too high. Plasma phosphorus was directly related to dietary phosphorus (Table 6). Hens fed .2% phosphorus had lower (P<.05) plasma phosphorus than those fed .6%. Significant differences were also found between birds fed .6 and 1.4% phosphorus. The relationship between a decrease in plasma phosphorus and the improvement in egg specific gravity has been reported by Miles and Harms (1982). The addition of .06 and .22% sodium from sodium bicarbonate resulted in an increase in specific gravity. The addition of .36% chloride to the diet had no effect on specific gravity or plasma phosphorus. Plasma calcium increased (P<.05) with each increase in dietary phosphorus. However, the rate of increase in plasma calcium declined at the higher levels of dietary phosphorus. These results contrast with those of Reichmann and Connor (1977) and Hunt and Chancey (1970). However, Paul and Snetsinger (1969) observed that feeding a phosphorus level below the hen's requirement resulted in a significant decrease in plasma calcium. Blood pH was not affected by dietary phosphorus even though plasma phosphorus concentration increased (P<.05) when dietary phosphorus increased from .2 to 1.4%. This finding suggests that laying hens are able to regulate their acid-base balance to compensate for the acidogenic effect that phosphorus has in the blood. The addition of .45% sodium did not affect blood pH of the hens fed .2 and 1.4% phosphorus. This is in agreement with Nesheim et al. (1964), who reported that excess sodium is not detrimental if chloride is also present in adequate amounts in the diet. Although no significant difference was found in plasma phosphorus when .36% chloride was added to the diet with 1.4% phosphorus, blood pH was lower. This can be explained if it is kept in mind that chloride in the blood has an acidogenic effect (Cohen et al., 1972; Cohen and Hurwitz, 1974). Base-excess (non-HCO^), bicarbonate, and total C 0 2 were inversely related to dietary phosphorus, decreasing as total phosphorus increased. The same trend was observed when chloride was added to the diets containing .2 and 1.4% phosphorus. The .45% sodium level did not affect pH of hens fed .2% phosphorus; however, an increase (P<.05) in base excess, bicarbonate, and total C 0 2 was found when .45%

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fed .2% phosphorus. However, the highest feed intake from hens fed 1.4% phosphorus was not related to the highest level of egg production. This finding suggests that the level of total phosphorus may have an influence on some feed intake controlling mechanism. Dietary phosphorus was found to have an influence (P<.05) on feed efficiency. Hens fed the diet containing .2% total phosphorus consumed significantly more feed per dozen eggs. These data agree with those of Ademosun and Kalango (1973) and Singsen et al. (1962), who found that feed efficiency was impaired when the total dietary phosphorus was reduced from .6 to .4%. Feed utilization was best when the diet contained .6% phosphorus as compared to diets containing .2 and 1.4% phosphorus. Feeding .2% phosphorus resulted in a decrease in egg weight. This was probably a result of the decreased feed consumption. These results do not agree with those of Walter and Aitken (1962), Singsen et al. (1962), Hurwitz and Bornstein (1963), Crowley et al. (1963), Hunt and Chancey (1970), and Reichmann and Connor (1977), who reported that low dietary levels of phosphorus did not affect egg weight. However, no difference in egg weight was found between the .6 and 1.4% phosphorus treatments. Level of dietary sodium did not affect egg weight. Phosphorus levels either above or below .6% depressed specific gravity. Singsen et al, (1962) and Hunt and Chancey (1970) reported that available phosphorus from .15 to .63% had no effect on specific gravity. However, several investigators obtained a decrease in eggshell quality when high phosphorus levels were fed (Damron et al., 1974; Harms and Miles, 1977). The possible explanation is that excess phosphorus acts as a crystal poison in the shell gland, thereby inhibiting the growth of calcite at the site of the forming shell (Hunt and Chancey, 1970). Bachra et al. (1963) reported that phosphorus ions inhibit calcium carbonate precipitation under physiological conditions. Supplemental sodium levels of .06 and .22% were beneficial (P«.05) in increasing eggshell specific gravity at phosphorus levels of .2 and 1.4%. The addition of .45% sodium decreased egg specific gravity when compared to levels of .06 and .22%. There is evidence that sodium can function in removing the excess phosphorus from the blood, resulting in better eggshell quality (Harms, 1979b; Miles and Harms,

PHOSPHORUS, SODIUM, CHLORIDE IN HEN DIETS

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TABLE 6. Plasma, calcium, phosphorus, and blood parameters when hens were fed different levels of sodium and chloride at three phosphorus levels, Experiment 2 Dietary phosphorus

Blood

Plasma Na or CI

Source

(%)

Ca -

P (mg/100 ml) e

Base excess

pH

(meq/liter)

d

HC0 3

a

Total C 0 2 (mmHg)

27.01 a

28.43 a

7.385 a b 7.348 b c

4.457 a 3.530 b

27.02 a 25.13 b

28.07 a 26.16b

4.71 c 4.80 c 4.55 c 4.55 c 4.73 c

7.392 a

3.770 b

26.30 a b

27.56 a

31.97 a 31.25 a b 30.32ab<: 30.28 a b c 29.oibcd

5.81 a 5.74 a 5.59 a b 5.31 a b 5.72 a

7.382 a b

2.416 c

23.78 c

24.94 c

7.390 a 7.309 c

4.810 a 1.440 d

26.70 a 22.87 c

28.14 a 24.12 c

22.54 c 28.91 b 30.96 a

1.83c 4.6 5 b 5.61 a

28.17 a 27.83 a 27.18 a 27.44 a

4.14 a 4.15 a 4.03 b 3.96 b

.00 .06 .22 .45 .36

NaHC0 3 NaHC0 3 NaHC0 3 NaHC0 3 HCl

22.96 22.90 e 22.75 e 21.66 e 22.52 e

1.89 1.90d 1.75 d 1.81 d 1.85 d

7.400

.60 .60 .60 .60 .60

.00 .06 .22 .45 .36

NaHC0 3 NaHC0 3 NaHCO, NaHC0 3 HCl

29.59abc 29.36 a b c 28.47 c d 28.21cd 26.55 d

1.40 1.40 1.40 1.40 1.40

.00 .06 .22 .45 .36

NaHC0 3 NaHC0 3 NaHC0 3 NaHC0 3 HCl

Among phosprlorus levels' .20 .60 1.40 Among so dium levels' .00 .06 .22 .45 nnr u 6

' ' ' ' Means within columns with different letters are significantly different (P<.05). 1

Does not contain the treatment with supplemental chloride as HCl.

sodium was added to the diet containing 1.4% phosphorus. It has been postulated that changes in blood acid-base balance, brought about by altering the sodium-chloride ratio in the diet, may also be a consequence of alteration of renal reabsorption of chloride and bicarbonate (Mongin, 1970; Cohen et al, 1972). REFERENCES Ademosun, A. A., and I. O. Kalango, 1973. Effect of calcium and phosphorus levels on the performance of layers in Nigeria. 1. Egg production, eggshell quality, feed intake and body weight. Poultry Sci. 52:1383-1392. Bachra, N. B., O. R. Trautz, and S. L. Simon, 1963. Precipitation of calcium carbonates and phosphates. 1. Spontaneous precipitation of calcium carbonates and phosphates under physiological conditions. Arch. Biochem. Biophys. 103:124. Bletner, J. K., and G. C. McGhee, 1975. The effect of phosphorus on egg specific gravity and other

production parameters. Poultry Sci. 54:1736. (Abstr.) Choi, J. H., R. D. Miles, and R. H. Harms, 1979. The response of serum inorganic phosphorus level in laying hens fed low levels of dietary phosphorus. Poultry Sci. 58:416-418. Cohen, I., and S. Hurwitz, 1974. The response of blood ionic constituents and acid-base balance to dietary sodium, potassium and chloride in laying hens. Poultry Sci. 53:378-383. Cohen, I., S. Hurwitz, and A. Bar, 1972. Acid-base balance sodium-to-chloride ratio in diets of laying hens. J.Nutr. 102:1-8. Cox, A. C , and S. L. Balloun, 1968. Lack of effect of sodium bicarbonate on shell characteristics. Poultry Sci. 47:1370-1371. Crowley, T. A., A. A. Kurnick, and B. L. Reid, 1963. Dietary phosphorus for laying hens. Poultry Sci. 42:758-765. Damron, B. L., A. R. Eldred, and R. H. Harms, 1974. The relationship of dietary phosphorus to eggshell quality. Poultry Sci. 53:1916. (Abstr.) El Boushy, A. R., 1979. Available phosphorus in poultry. 1. Effect of phosphorus levels on the

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4.559 a

.20 .20 .20 .20 .20

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