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The Effects of Dietary Phosphorus on Productive Performance and Egg Quality of Ten Strains of White Leghorns1
The Effects of Dietary Phosphorus on Productive Performance and Egg Quality of Ten Strains of White Leghorns1 R. M. G. HAMILTON and I. R. SIBBALD Animal Research Institute, Agriculture Canada, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6 (Received for publication November 18, 1976)
Poultry Science 56:1221-1228, 1977 INTRODUCTION There is a lack of agreement concerning the optimum level of dietary phosphorus for the laying hen. In the United Kingdom the recommended allowance is 0.35% non-phytate phosphorus (A.R.C., 1975), where it is assumed that phytate phosphorus in practical diets is completely unavailable to the laying hen. The N.A.S.-N.R.C. (1971), however, recommend 0.6% available phosphorus, which is defined as the sum of the inorganic phosphorus plus 30% of the phytate phosphorus. Summers et al. (1976) reported that 0.25 to 0.35% available or 0.1 to 0.2% non-phytate phosphorus were adequate for optimum egg production by caged laying hens between 36 and 52 weeks of age. There was an indication that more than 0.25% available or 0.1% nonphytate phosphorus may be detrimental to egg shell quality as measured by deformation on eggs from hens between 48 and 52 weeks of age. It should be noted that Summers et al. (1976) consider 50% of phytate phosphorus to be available to the laying hen. Singsen et al. (1962), Walter and Aitken (1962), Crowley et al. (1968) and Hunt and Chancey (1970) have
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tute.
Contribution number 670, Animal Research Insti-
found that 0.38% available phosphorus (0.01 to 0.3% non-phytate phosphorus) was adequate for peak egg production in White Leghorn hens of various ages and that lower levels had no significant effects on body weight, feed efficiency, egg weight or egg shell quality. In fact, the results of Summers et al. (1976) and Hunt and Chancey (1970) indicate that the laying hen can utilize phytate phosphorus to meet her requirements. Many experiments on the phosphorus requirements of laying hens have not covered a complete laying year while others have involved a limited number of genotypes. There is a limited amount of information about the effects of phosphorus on shell quality particularly towards the end of the laying year. The experiment described in the present report investigated the effects of phosphorus on egg production, egg quality, feed consumption and feed efficiency of ten strains of S.C.W.L. hens over a 357-day laying period. MATERIALS AND METHODS One thousand five hundred and thirty-six White Leghorn pullets were housed in individual wire cages (26.4 X 40.6 cm.) at 140 d. of age. There were 144 birds from each of 9 strains and 244 from a control strain (7 X 7). The strains represented three widely used com-
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ABSTRACT One thousand five hundred and thirty-six individually caged S.C.W.L. hens were fed corn, wheat, soybean diets formulated to contain 0.55, 0.50, 0.45 and 0.40% available or 0.47, 0.43, 0.38 and 0.33% inorganic phosphorus from 140 to 497 d. of age. The hens were from three commercial strains, three 2-way and three 3-way strain crosses and from a control strain. Egg quality measurements were taken on eggs laid over 5 d. intervals seven times during the experiment. Chemical analyses indicated that the diets fed contained 0.58, 0.55, 0.50 and 0.45% available and 0.48, 0.45, 0.42 and 0.38% inorganic phosphorus. Phosphorus level had no significant effect on feed intake or efficiency, egg production, sexual maturity, egg weight, blood spots or mortality but had a significant effect on 497 d. body weight and egg specific gravity at 165, 225, 277, 335, 390, 445 and 490 d.j however, the differences were small for this latter trait and probably of little practical importance. Strain of bird had a significant effect on all traits except mortality and blood spots. There were very few diet X strain interactions. The results indicate that a level of 0.45% available phosphorus is adequate for laying hens under practical conditions.
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HAMILTON AND SIBBALD 125 d. of age. Some of the birds received insoluble granite grit during the brooding and rearing periods; no grit was fed in the laying house. Sibbald and Gowe (1977), working with birds from the same flock, showed that grit during the brooding and rearing periods had no effects on subsequent sexual maturity, egg production or egg quality; consequently, it is reasonable to assume that differences observed in this experiment were due to the treatments and were not carried over from the rearing period. Four experimental diets were randomly assigned within each of four replicates with birds of each strain being equally distributed between diets and replicates. The diets which were formulated to contain by calculation 0.55, 0.50, 0.45 and 0.40% of available phosphorus (0.47, 0.43, 0.38 and 0.33% of non-phytate phosphorus) are described in Table 1. The
TABLE 1. — Composition of experimental diets Level of available phosphorus 1 Ingredients
0.58%
Basal2 Dicalcium phosphate 3 Pulverized limestone 3 Ground wheat
90.00 1.85 7.42 0.73
Protein (N X 6.25) Calculated Found
15.6 16.1
0.55% 90.00 1.60 7.54 0.86
±0.6 4
15.6 15.9
±0.4
0.50%
0.45%
90.00 1.36 7.65 0.99
90.00 1.12 7.77 1.11
15.6 16.2 ± 0.4
15.6 15.6
±0.7
Calcium, % Calculated Found
3.25 3.09 ±0.33
3.25 3.23 ±0.22
3.25 3.23 ±0.22
3.25 3.38 ± 0.40
Total phosphorus, % Calculated Found
0.69 0.70 ± 0.03
0.64 0.67 ± 0.05
0.59 0.64 ± 0.02
0.54 0.60 ± 0.06
Phytate phosphorus, % Calculated Found
0.21 0.22 ± 0.01
0.21 0.22 ± 0.02
0.21 0.22 ± 0.1
0.21 0.22 + 0.01
Available phosphorus, % Calculated5 Found
0.55 0.58 + 0.03
0.50 0.55 ± 0.04
0.45 0.50 ± 0.01
0.40 0.45 ± 0.02
1
Based on chemical analyses and are same as final line of table. Basal diet contained: corn, 20.86; wheat, 59.4;soybean meal (50% protein), 13.9; dehydrated alfalfa, 3.3; dried whey, 1.1; iodized salt, 0.55; DL-methionine, 0.11; and vitamin-mineral premix, 0.78. Vitamin-mineral premix supplied per kg. of feed: vitamin A, 5500 I.U.; vitamin D 3 , 1100 I.C.U.; vitamin E, 3.3 I.U.; vitamin K, 1.1 mg.; riboflavin, 4.4 mg.; niacin, 22.0 mg.; calcium pantothenate, 5.5 mg.; folacin, 1.1 mg.; choline chloride, 220 mg.; vitamin B, 2 , 5.5 gm.; manganese, 55.0 mg.; zinc, 44.0 mg.; copper, 5.5 mg.; and iodine, 1.1 mg. 3 The dicalcium phosphate contained, by chemical analyses, 16.47 ± 0.68% calcium and 20.07 ± 1.26% phosphorus (n = 10) and the limestone 38.37 ± 1.72% calcium (n = 10). 4 Means ± S.D. based on the analyses of 6 or 7 samples of each diet. 5 Defined as total phosphorus minus 50% of the phytate phosphorus. 2
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mercial strains (OA, OB and OD), three 2-way experimental strain crosses (2 X 3 , 3 x 2 and 4 X 1) and three 3-way experimental strain crosses [(1) X (2 X 3), (8) X (4 X 1) and (9) X (1 X 8 ) ] . The commercial strains were Babcock B300, H&N Nickchick and Shaver 288. The remaining birds have been described previously (Sibbald and Gowe, 1977). During the brooding (0 to 56 d.) and rearing (57 to 139 d.) periods the chicks were group housed in wire cages and reared under a constant 6 h. day with dim (1.6 lux) red lights. After 126 d. the day length was increased by 30 minutes per week up to a maximum of 16 h. per day and at 140 d. the red lights were replaced with white lights (40 lux). All chicks were vaccinated for Marek's disease at hatching, for bronchitis and Newcastle disease at 12 and 112 d., and for avian encephalomyelitis at 80 d.; the pullets were dubbed and dewattled at
DIETARY PHOSPHORUS LEVELS
Feed consumption, egg production and mortality were recorded daily. The mass and number of eggs laid on Tuesday and Wednesday of each week were recorded. The eggs laid during 5-d. periods were saved for shell and interior quality measurements when the hens were 165, 225, 277, 335, 390, 445 and 490 d. of age. Shell quality was assessed by the specific gravity (S.G.) floatation procedure using salt solutions that varied in S.G. from 1.062 to 1.102 by increments of 0.004. Other egg quality parameters measured were egg weight, albumen height and blood spots. The means of egg quality traits of the eggs collected for each period from each individual hen were used for the statistical analyses. Feed consumption data were obtained for diet groups within each replicate but were not available for strains of birds. The consumption and efficiency (feed/dozen eggs, feed/kg. egg) data were analyzed according to a randomized
complete block design as outlined by Steel and Torrie (1960). Analysis of variance was performed on egg production, age at first egg (A.F.E.) 140 and 497 d. body weights, mortality and egg quality traits using replicates, diets and type of strain as cross-classified main effects. Type of strain was subdivided into commercial, 2-way crosses and 3-way crosses and interactions between strain types and diets were computed. The method of Harvey (1960) was used for the analysis.
RESULTS AND DISCUSSION The results of the chemical analyses of the feed samples are summarized in Table 1. There was a considerable amount of variation in both dietary calcium and total phosphorus levels but the observed means are in close agreement with the calculated values. The amount of available phosphorus in the diets was consistently greater than that calculated; consequently, the minimum level of available phosphorus was 0.45 rather than 0.40 percent. These results stress the importance of direct chemical measurements when attempting to delineate nutrient requirements and agree with the results of Bayley et al. (1975). A small but significant linear increase in the apparent metabolizable energy value was found as the level of phosphorus in these diets was decreased (Sibbald and Hamilton, 1977). Variation in dietary phosphorus levels had no effect (P>0.05) on either feed consumption or feed efficiency (Table 2). Davidson and Boyne (1970) and Ademosun and Kalango (1973) also found that phosphorus levels did not affect feed intake while Summers et al. (1976) observed that feed intake was depressed
TABLE 2. — Effect of dietary phosphorus level on feed intake and efficiency Feed efficiency2 Phosphorus level1
Feed consumption2
kg. feed/ dozen
kg. feed/ kg- egg
% 0.58 0.55 0.50 0.45
gm ./bird/day 111 110 110 110
1.80 1.79 1.81 1.77
2.59 2.58 2.63 2.58
1 1
Available phosphorus based on chemical determinations. Mean values over the 140 to 497 d. laying period.
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phosphorus from plant material was assumed to be 50% available to the laying hen (Summers et al, 1976). Variation in dietary phosphorus was accomplished by reducing the dicalcium phosphate supplement while the calcium level was maintained at 3.25% by the addition of pulverized limestone. Feed and water were provided ad libitum throughout the 357 d. laying period. Samples of each mix of each diet were taken and analyzed for Kjeldahl nitrogen, calcium and total phosphorus by the methods of A.O.A.C. (1965). Phytate phosphorus was determined by the method of MaCance and Widdowran (1937) except concentrated sulphuric and nitric acid (1:1 v./v.) was used to digest the ferric phytate precipitate as reported by Oshima et al. (1964). The phosphorus content of the digest was determined by the method of A.O.A.C. (1965).
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HAMILTON AND SIBBALD strain X diet interaction cannot be discarded. The various production data suggest that occurrence of a meaningful interaction was unlikely, although there was a highly significant (P<0.01) strain effect on body weight. At the time of housing (140 d.) there were no differences in body weights (P>0.05) between phosphorus levels (Table 3). This confirms the effectiveness of the randomization procedure. There were body weight differences between strains at the start of the experiment. At the conclusion of the experiment (497 d.) there was a significant (P<0.01) difference in body weights between phosphorus levels (Table 3); however, there was no consistent trend. The maximum difference between treat -
TABLE 3. — Effect of dietary phosphorus level and strain on body -weight, sexual maturity, egg production and mortality Production No. birds housed
P Level2 0.58% 0.55 0.50 0.45 Grand mean Strain (7) X (7)
384 384 384 384
240
OA OB OD Mean
144 144 144
(2)X(3) (3)X(2) (4)X(1) Mean
144 144 144
(1) X (2X3) (8)X (4X1) (9) X (1X8) Mean
144 144 144
Body weight
1
Mortality
%
%
NS 76.8 76.9 76.3 76.6 76.6
NS 5.5 7.1 7.6 6.2 6.6
497 d.
A.F.E.
kgNS 3 1.48 1.48 1.48 1.47 1.48
kg-
d.
** 1.87 1.88 1.90 1.84 1.87
NS 155 155 156 155 155
NS 254 250 249 257 253
***
***
** *
***
* **
1.36
1.72
230
71.4
«*«<
***
161 NS 158 156 158 157 NS 148 150 149 149
*
***
1.37 1.36 1.27 1.33 NS 4 1.60 1.61 1.59 1.60
1.72 1.74 1.60 1.69
***
1.57 1.56 1.49 1.54
1.95 1.88 2.09 1.97 NS 1.93 1.83 1.90 1.89
1.48 ±0.50
1.84 ±0.75
***
NS 10.3 NS 10.4 5.5 5.6 7.2
258 270 250 259 NS 276 265 261 267
80.1 82.6 76.6 79.8 NS 80.0 77.5 78.3 78.6
* + *
***
*
78.9 76.2 75.1 76.7
11.1 4.1 3.5 6.2
76.6 ±0.3
6.6 ±0.6
149 151 160 153
258 261 242 254
155 ±0.3
253 ±1.6
Production over the period from first egg. Available phosphorus level based on chemical analyses. 3 NS nonsignificant, *P<0.05, **P<0.01, ***P<0.005. 4 Indicates the statistical contribution of strain to the main effect of strain type. 5 Standard error of the mean for all phosphorus levels and strains. 2
Hen day1
140 d.
***4
Grand mean S.E.M.5
Hen housed
* 2.1 4.2 9.0 5.1
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only when the available phosphorus was reduced to 0.15% (0% inorganic phosphorus). Hurwitz and Bornstein (1963) reported a reduction in feed consumption when dietary total phosphorus was reduced from 0.72 to 0.32 percent. The feed efficiency results (Table 2) agree with those of Summers et al. (1976), Hunt and Chancey (1970) and Walter and Aitken (1962) but are not in agreement with those of Ademosun and Kalango (1973) and Singsen et al. (1962) who found that feed efficiency was impaired when the total phosphorus in the diet was reduced from 0.6 to 0.4 percent. It was impractical to collect feed consumption data for strains within dietary treatments; consequently, the possibility of a
DIETARY PHOSPHORUS LEVELS
Strain had no effect (P>0.05) on mortality but had highly significant (P<0.005) effects on sexual maturity and egg production (Table 3). The hens of the 2-way strain crosses came into lay, on average, 8 days before the commercial strains and 4 days before the 3-way crosses. There were no strain X phosphorus level interactions among the A.F.E. data. Both henhoused and hen-day production varied between strains (P<0.005) but again there were no interactions between strains and phosphorus levels (P>0.05). The 2-way strain crosses had the greatest hen-housed production while the commercial strains had the greatest hen-day production. The difference in hen-housed production between the 2-way strain crosses and the commercial birds may reflect, in part, the difference in age at first egg. Egg shell quality was measured seven times during the experiment. The mean S.G. of the eggs laid by an individual hen during a 5 d. period was the unit of measurement. The
results are summarized in Table 4. The dietary phosphorus level had a significant effect on S.G. on each occasion; however, the effect was not consistent and the differences were so small as to be of questionable practical importance. Walter and Aitken (1962), Singsen et al. (1962) and Hunt and Chancey (1970) reported that similar ranges of dietary phosphorus (0.15 to 0.63% available or 0.01 to 0.56 inorganic) had no effects on specific gravity. Egg shell quality differed between strains (P<0.005) largely because of the variation between the commercial strains. There was only one minor strain X phosphorus level interaction which was found in the 165 d. data; this may have been a random occurrence. Egg weights, Haugh units and the incidence of blood spots for each of the seven periods followed a similar pattern; consequently, mean results for only 165 d., 277 d., 390 d., and 490 d. are presented in Table 5. Dietary phosphorus level had no significant (P>0.05) effects on egg weight, blood spots or Haugh units after 225 d. but did have an unexplained effect (P<0.05) on Haugh units at 165 days. Walter and Aitken (1962), Singsen et al. (1962), Hurwitz and Bornstein (1963), Crowley et al. (1963), Hunt and Chancey (1970) and Davidson and Boyne (1970) have previously found dietary phosphorus to have little effect on egg weight. Although strain had a profound effect upon egg weight there was no strain x phosphorus level interactions associated with this variable. There were several strain effects on interior egg quality as measured by Haugh units but the only interaction with dietary phosphorus level was small and occurred at 165 days. The incidence of blood spots varied (P<0.05) between strains at 390 d., the difference being largely among the 3-way strain crosses. There was a strain x dietary phosphorus level interaction (P<0.05) at 165 d. which was primarily attributable to variation among the 2-way strain crosses. A similar interaction between dietary phosphorus and the 3-way strain crosses explains the strain X diet interaction at 277 days. The results of this experiment indicate that S.C.W.L. hens reared and housed in wire cages probably have dietary phosphorus requirements below those listed by the A.R.C. and the N.A.S.-N.R.C. An available phosphorus (inorganic + 50% phytate phosphorus) level calculated to be 0.40% but found to be 0.45% proved to be just as satisfactory as higher dietary levels. The low incidence of strain X
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ment means (60 g.) was small. Both Walter and Aitken (1962) and Hurwitz and Bornstein (1963) have found dietary phosphorus level to affect weight gain during the laying period. Strain had a highly significant (P<0.005) effect on body weight at 497 d. but there was no significant (P>.05) phosphorus level X strain interactions. The body weights of the various strains span the range likely to be found under practical conditions. The effects of strain on body weight are in agreement with those observed by Sibbald and Gowe (1977) on birds drawn from the same populations. Sexual maturity, expressed as age at first egg (A.F.E.), egg production and mortality were not affected (P>0.05) by the level of dietary phosphorus. Summers et al. (1976), Davidson and Boyne (1970), Hunt and Chancey (1970), Crowley et al. (1963) and Walter and Aitken (1962) also found that egg production was not affected by dietary phosphorus levels of 0.15 to 0.63% available or 0.01 to 0.56% inorganic phosphorus; whereas, Ademosun and Kalango (1973), Hurwitz and Bornstein (1963) and Singsen et al. (1962) found that decreasing phosphorus levels from 0.55% to 0.15% available or 0.34% to 0 inorganic phosphorus resulted in lower egg production. The mortality data (Table 3) agree with the results of Walter and Aitken (1962) but not with those of Crowley et al. (1963) and Singsen et al. (1962) who observed lower mortality when dietary phosphorus levels were decreased.
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diet interactions suggests t h a t t h e findings could be applied with confidence u n d e r practical conditions. ACKNOWLEDGEMENTS
REFERENCES Ademosun, A. A., and I. O. Kalango, 1973. Effect of calcium anrd phosphorus levels on the performances of layers in Nigeria. 1. Egg production, egg shell quality, feed intake and body weight. Poultry Sci. 52:1383-1392. Agricultural Research Council (London), 1975. The Nutrient Requirements of Farm Livestock. I. Poultry. Association of Official Agricultural Chemists, 1965. Official Methods of Analysis, 10 ed. Washington, DC. Bayley, H. S., D. Arthur, G. H. Bowmann, J. Pos and R. G. Thomson, 1975. Influence of dietary phosphorus level on growth and bone development in boars and gilts. J. Anim. Sci. 40:864-870. Crowley, T. A., A. A. Kurnick and B. L. Reid, 1963. Dietary phosphorus for laying hens. Poultry Sci. 42:758-765. Davidson, J., and A. W. Boyne, 1970. The calcium and
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The a u t h o r s wish t o t h a n k L. Asselstine for his capable assistance with t h e data files, t o R. W. Bougie, R. T. Poirier and R. A. Arcand for their technical assistance and t o K. Hilson, Drs. A. J. McAllister and W. Lentz for assistance with t h e statistical analyses and t o Dr. I. Motzok, D e p a r t m e n t of Nutrition, University of Guelph for his advice o n t h e d e t e r m i n a t i o n of p h y t a t e p h o s p h o r u s . T h e chemical analyses of feed samples were performed b y t h e staff of t h e Chemical and Biological Research Institute, Agriculture Canada.
phosphorus requirements of laying hens. Br. J. Nutr. 11:231-240. Harvey, W. R., 1960. Least squares analysis of data with unequal subclass numbers. United States Dept. Agric. Pub. A.R.S. 2 0 - 8 . Hunt, J. R., and H. W. R. Chancey, 1970. Influence of dietary phosphorus on shell quality. Br. Poultry Sci. 11:259-267. Hurwitz, S., and S. Bornstein, 1963. The effect of calcium and phosphorus in the diet of laying hens on egg production and shell quality. Israel J. Agric. Res. 13:147-154. McCance, R. A., and E. M. Widdowran, 1937. CCCXX. P h y t i n in human nutrition. Biochem. J. 29:2694-2699. National Academy of Sciences—National Research Council, 1971. Nutrient Requirements of Domestic Animals. I. Nutrient requirements of poultry, 6 ed. Washington, DC. Oshima, M., T. G. Taylor and A. Williams, 1964. Variations in the concentration phytic acid in the blood of the domestic fowl. Biochem. J. 92:42-46. Sibbald, I. R., and R. S. Gowe, 1977. Effects of insoluble grit on the productive performance of ten White Leghorn strains. Br. Poultry Sci. In press. Sibbald, I. R., and R. M. G. Hamilton, 1977. The effect of dietary phosphorus levels and strain of bird on apparent metabolizable energy content of a laying hen diet. Poultry Sci. 56:378-380. Singsen, E. P., A. H. Spandorf, L. D. Matterson, J. A. Serafin and J. J. Tlustohowicz, 1962. Phosphorus in the nutrition of the adult hen. 1. Minimum p h o s p h o r u s r e q u i r e m e n t s . P o u l t r y Sci. 41:1401-1414. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., Toronto, Canada. Summers, J. D., R. Grandhi and S. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-^13. Walter, E. D., and J. R. Aitken, 1962. Phosphorus requirements of laying hens confined to cages. Poultry Sci. 4 1 : 3 8 6 - 3 9 0 .
Poultry Science 56:1221-1228, 1977 INTRODUCTION There is a lack of agreement concerning the optimum level of dietary phosphorus for the laying hen. In the United Kingdom the recommended allowance is 0.35% non-phytate phosphorus (A.R.C., 1975), where it is assumed that phytate phosphorus in practical diets is completely unavailable to the laying hen. The N.A.S.-N.R.C. (1971), however, recommend 0.6% available phosphorus, which is defined as the sum of the inorganic phosphorus plus 30% of the phytate phosphorus. Summers et al. (1976) reported that 0.25 to 0.35% available or 0.1 to 0.2% non-phytate phosphorus were adequate for optimum egg production by caged laying hens between 36 and 52 weeks of age. There was an indication that more than 0.25% available or 0.1% nonphytate phosphorus may be detrimental to egg shell quality as measured by deformation on eggs from hens between 48 and 52 weeks of age. It should be noted that Summers et al. (1976) consider 50% of phytate phosphorus to be available to the laying hen. Singsen et al. (1962), Walter and Aitken (1962), Crowley et al. (1968) and Hunt and Chancey (1970) have
1
tute.
Contribution number 670, Animal Research Insti-
found that 0.38% available phosphorus (0.01 to 0.3% non-phytate phosphorus) was adequate for peak egg production in White Leghorn hens of various ages and that lower levels had no significant effects on body weight, feed efficiency, egg weight or egg shell quality. In fact, the results of Summers et al. (1976) and Hunt and Chancey (1970) indicate that the laying hen can utilize phytate phosphorus to meet her requirements. Many experiments on the phosphorus requirements of laying hens have not covered a complete laying year while others have involved a limited number of genotypes. There is a limited amount of information about the effects of phosphorus on shell quality particularly towards the end of the laying year. The experiment described in the present report investigated the effects of phosphorus on egg production, egg quality, feed consumption and feed efficiency of ten strains of S.C.W.L. hens over a 357-day laying period. MATERIALS AND METHODS One thousand five hundred and thirty-six White Leghorn pullets were housed in individual wire cages (26.4 X 40.6 cm.) at 140 d. of age. There were 144 birds from each of 9 strains and 244 from a control strain (7 X 7). The strains represented three widely used com-
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ABSTRACT One thousand five hundred and thirty-six individually caged S.C.W.L. hens were fed corn, wheat, soybean diets formulated to contain 0.55, 0.50, 0.45 and 0.40% available or 0.47, 0.43, 0.38 and 0.33% inorganic phosphorus from 140 to 497 d. of age. The hens were from three commercial strains, three 2-way and three 3-way strain crosses and from a control strain. Egg quality measurements were taken on eggs laid over 5 d. intervals seven times during the experiment. Chemical analyses indicated that the diets fed contained 0.58, 0.55, 0.50 and 0.45% available and 0.48, 0.45, 0.42 and 0.38% inorganic phosphorus. Phosphorus level had no significant effect on feed intake or efficiency, egg production, sexual maturity, egg weight, blood spots or mortality but had a significant effect on 497 d. body weight and egg specific gravity at 165, 225, 277, 335, 390, 445 and 490 d.j however, the differences were small for this latter trait and probably of little practical importance. Strain of bird had a significant effect on all traits except mortality and blood spots. There were very few diet X strain interactions. The results indicate that a level of 0.45% available phosphorus is adequate for laying hens under practical conditions.
1222
HAMILTON AND SIBBALD 125 d. of age. Some of the birds received insoluble granite grit during the brooding and rearing periods; no grit was fed in the laying house. Sibbald and Gowe (1977), working with birds from the same flock, showed that grit during the brooding and rearing periods had no effects on subsequent sexual maturity, egg production or egg quality; consequently, it is reasonable to assume that differences observed in this experiment were due to the treatments and were not carried over from the rearing period. Four experimental diets were randomly assigned within each of four replicates with birds of each strain being equally distributed between diets and replicates. The diets which were formulated to contain by calculation 0.55, 0.50, 0.45 and 0.40% of available phosphorus (0.47, 0.43, 0.38 and 0.33% of non-phytate phosphorus) are described in Table 1. The
TABLE 1. — Composition of experimental diets Level of available phosphorus 1 Ingredients
0.58%
Basal2 Dicalcium phosphate 3 Pulverized limestone 3 Ground wheat
90.00 1.85 7.42 0.73
Protein (N X 6.25) Calculated Found
15.6 16.1
0.55% 90.00 1.60 7.54 0.86
±0.6 4
15.6 15.9
±0.4
0.50%
0.45%
90.00 1.36 7.65 0.99
90.00 1.12 7.77 1.11
15.6 16.2 ± 0.4
15.6 15.6
±0.7
Calcium, % Calculated Found
3.25 3.09 ±0.33
3.25 3.23 ±0.22
3.25 3.23 ±0.22
3.25 3.38 ± 0.40
Total phosphorus, % Calculated Found
0.69 0.70 ± 0.03
0.64 0.67 ± 0.05
0.59 0.64 ± 0.02
0.54 0.60 ± 0.06
Phytate phosphorus, % Calculated Found
0.21 0.22 ± 0.01
0.21 0.22 ± 0.02
0.21 0.22 ± 0.1
0.21 0.22 + 0.01
Available phosphorus, % Calculated5 Found
0.55 0.58 + 0.03
0.50 0.55 ± 0.04
0.45 0.50 ± 0.01
0.40 0.45 ± 0.02
1
Based on chemical analyses and are same as final line of table. Basal diet contained: corn, 20.86; wheat, 59.4;soybean meal (50% protein), 13.9; dehydrated alfalfa, 3.3; dried whey, 1.1; iodized salt, 0.55; DL-methionine, 0.11; and vitamin-mineral premix, 0.78. Vitamin-mineral premix supplied per kg. of feed: vitamin A, 5500 I.U.; vitamin D 3 , 1100 I.C.U.; vitamin E, 3.3 I.U.; vitamin K, 1.1 mg.; riboflavin, 4.4 mg.; niacin, 22.0 mg.; calcium pantothenate, 5.5 mg.; folacin, 1.1 mg.; choline chloride, 220 mg.; vitamin B, 2 , 5.5 gm.; manganese, 55.0 mg.; zinc, 44.0 mg.; copper, 5.5 mg.; and iodine, 1.1 mg. 3 The dicalcium phosphate contained, by chemical analyses, 16.47 ± 0.68% calcium and 20.07 ± 1.26% phosphorus (n = 10) and the limestone 38.37 ± 1.72% calcium (n = 10). 4 Means ± S.D. based on the analyses of 6 or 7 samples of each diet. 5 Defined as total phosphorus minus 50% of the phytate phosphorus. 2
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mercial strains (OA, OB and OD), three 2-way experimental strain crosses (2 X 3 , 3 x 2 and 4 X 1) and three 3-way experimental strain crosses [(1) X (2 X 3), (8) X (4 X 1) and (9) X (1 X 8 ) ] . The commercial strains were Babcock B300, H&N Nickchick and Shaver 288. The remaining birds have been described previously (Sibbald and Gowe, 1977). During the brooding (0 to 56 d.) and rearing (57 to 139 d.) periods the chicks were group housed in wire cages and reared under a constant 6 h. day with dim (1.6 lux) red lights. After 126 d. the day length was increased by 30 minutes per week up to a maximum of 16 h. per day and at 140 d. the red lights were replaced with white lights (40 lux). All chicks were vaccinated for Marek's disease at hatching, for bronchitis and Newcastle disease at 12 and 112 d., and for avian encephalomyelitis at 80 d.; the pullets were dubbed and dewattled at
DIETARY PHOSPHORUS LEVELS
Feed consumption, egg production and mortality were recorded daily. The mass and number of eggs laid on Tuesday and Wednesday of each week were recorded. The eggs laid during 5-d. periods were saved for shell and interior quality measurements when the hens were 165, 225, 277, 335, 390, 445 and 490 d. of age. Shell quality was assessed by the specific gravity (S.G.) floatation procedure using salt solutions that varied in S.G. from 1.062 to 1.102 by increments of 0.004. Other egg quality parameters measured were egg weight, albumen height and blood spots. The means of egg quality traits of the eggs collected for each period from each individual hen were used for the statistical analyses. Feed consumption data were obtained for diet groups within each replicate but were not available for strains of birds. The consumption and efficiency (feed/dozen eggs, feed/kg. egg) data were analyzed according to a randomized
complete block design as outlined by Steel and Torrie (1960). Analysis of variance was performed on egg production, age at first egg (A.F.E.) 140 and 497 d. body weights, mortality and egg quality traits using replicates, diets and type of strain as cross-classified main effects. Type of strain was subdivided into commercial, 2-way crosses and 3-way crosses and interactions between strain types and diets were computed. The method of Harvey (1960) was used for the analysis.
RESULTS AND DISCUSSION The results of the chemical analyses of the feed samples are summarized in Table 1. There was a considerable amount of variation in both dietary calcium and total phosphorus levels but the observed means are in close agreement with the calculated values. The amount of available phosphorus in the diets was consistently greater than that calculated; consequently, the minimum level of available phosphorus was 0.45 rather than 0.40 percent. These results stress the importance of direct chemical measurements when attempting to delineate nutrient requirements and agree with the results of Bayley et al. (1975). A small but significant linear increase in the apparent metabolizable energy value was found as the level of phosphorus in these diets was decreased (Sibbald and Hamilton, 1977). Variation in dietary phosphorus levels had no effect (P>0.05) on either feed consumption or feed efficiency (Table 2). Davidson and Boyne (1970) and Ademosun and Kalango (1973) also found that phosphorus levels did not affect feed intake while Summers et al. (1976) observed that feed intake was depressed
TABLE 2. — Effect of dietary phosphorus level on feed intake and efficiency Feed efficiency2 Phosphorus level1
Feed consumption2
kg. feed/ dozen
kg. feed/ kg- egg
% 0.58 0.55 0.50 0.45
gm ./bird/day 111 110 110 110
1.80 1.79 1.81 1.77
2.59 2.58 2.63 2.58
1 1
Available phosphorus based on chemical determinations. Mean values over the 140 to 497 d. laying period.
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phosphorus from plant material was assumed to be 50% available to the laying hen (Summers et al, 1976). Variation in dietary phosphorus was accomplished by reducing the dicalcium phosphate supplement while the calcium level was maintained at 3.25% by the addition of pulverized limestone. Feed and water were provided ad libitum throughout the 357 d. laying period. Samples of each mix of each diet were taken and analyzed for Kjeldahl nitrogen, calcium and total phosphorus by the methods of A.O.A.C. (1965). Phytate phosphorus was determined by the method of MaCance and Widdowran (1937) except concentrated sulphuric and nitric acid (1:1 v./v.) was used to digest the ferric phytate precipitate as reported by Oshima et al. (1964). The phosphorus content of the digest was determined by the method of A.O.A.C. (1965).
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HAMILTON AND SIBBALD strain X diet interaction cannot be discarded. The various production data suggest that occurrence of a meaningful interaction was unlikely, although there was a highly significant (P<0.01) strain effect on body weight. At the time of housing (140 d.) there were no differences in body weights (P>0.05) between phosphorus levels (Table 3). This confirms the effectiveness of the randomization procedure. There were body weight differences between strains at the start of the experiment. At the conclusion of the experiment (497 d.) there was a significant (P<0.01) difference in body weights between phosphorus levels (Table 3); however, there was no consistent trend. The maximum difference between treat -
TABLE 3. — Effect of dietary phosphorus level and strain on body -weight, sexual maturity, egg production and mortality Production No. birds housed
P Level2 0.58% 0.55 0.50 0.45 Grand mean Strain (7) X (7)
384 384 384 384
240
OA OB OD Mean
144 144 144
(2)X(3) (3)X(2) (4)X(1) Mean
144 144 144
(1) X (2X3) (8)X (4X1) (9) X (1X8) Mean
144 144 144
Body weight
1
Mortality
%
%
NS 76.8 76.9 76.3 76.6 76.6
NS 5.5 7.1 7.6 6.2 6.6
497 d.
A.F.E.
kgNS 3 1.48 1.48 1.48 1.47 1.48
kg-
d.
** 1.87 1.88 1.90 1.84 1.87
NS 155 155 156 155 155
NS 254 250 249 257 253
***
***
** *
***
* **
1.36
1.72
230
71.4
«*«<
***
161 NS 158 156 158 157 NS 148 150 149 149
*
***
1.37 1.36 1.27 1.33 NS 4 1.60 1.61 1.59 1.60
1.72 1.74 1.60 1.69
***
1.57 1.56 1.49 1.54
1.95 1.88 2.09 1.97 NS 1.93 1.83 1.90 1.89
1.48 ±0.50
1.84 ±0.75
***
NS 10.3 NS 10.4 5.5 5.6 7.2
258 270 250 259 NS 276 265 261 267
80.1 82.6 76.6 79.8 NS 80.0 77.5 78.3 78.6
* + *
***
*
78.9 76.2 75.1 76.7
11.1 4.1 3.5 6.2
76.6 ±0.3
6.6 ±0.6
149 151 160 153
258 261 242 254
155 ±0.3
253 ±1.6
Production over the period from first egg. Available phosphorus level based on chemical analyses. 3 NS nonsignificant, *P<0.05, **P<0.01, ***P<0.005. 4 Indicates the statistical contribution of strain to the main effect of strain type. 5 Standard error of the mean for all phosphorus levels and strains. 2
Hen day1
140 d.
***4
Grand mean S.E.M.5
Hen housed
* 2.1 4.2 9.0 5.1
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only when the available phosphorus was reduced to 0.15% (0% inorganic phosphorus). Hurwitz and Bornstein (1963) reported a reduction in feed consumption when dietary total phosphorus was reduced from 0.72 to 0.32 percent. The feed efficiency results (Table 2) agree with those of Summers et al. (1976), Hunt and Chancey (1970) and Walter and Aitken (1962) but are not in agreement with those of Ademosun and Kalango (1973) and Singsen et al. (1962) who found that feed efficiency was impaired when the total phosphorus in the diet was reduced from 0.6 to 0.4 percent. It was impractical to collect feed consumption data for strains within dietary treatments; consequently, the possibility of a
DIETARY PHOSPHORUS LEVELS
Strain had no effect (P>0.05) on mortality but had highly significant (P<0.005) effects on sexual maturity and egg production (Table 3). The hens of the 2-way strain crosses came into lay, on average, 8 days before the commercial strains and 4 days before the 3-way crosses. There were no strain X phosphorus level interactions among the A.F.E. data. Both henhoused and hen-day production varied between strains (P<0.005) but again there were no interactions between strains and phosphorus levels (P>0.05). The 2-way strain crosses had the greatest hen-housed production while the commercial strains had the greatest hen-day production. The difference in hen-housed production between the 2-way strain crosses and the commercial birds may reflect, in part, the difference in age at first egg. Egg shell quality was measured seven times during the experiment. The mean S.G. of the eggs laid by an individual hen during a 5 d. period was the unit of measurement. The
results are summarized in Table 4. The dietary phosphorus level had a significant effect on S.G. on each occasion; however, the effect was not consistent and the differences were so small as to be of questionable practical importance. Walter and Aitken (1962), Singsen et al. (1962) and Hunt and Chancey (1970) reported that similar ranges of dietary phosphorus (0.15 to 0.63% available or 0.01 to 0.56 inorganic) had no effects on specific gravity. Egg shell quality differed between strains (P<0.005) largely because of the variation between the commercial strains. There was only one minor strain X phosphorus level interaction which was found in the 165 d. data; this may have been a random occurrence. Egg weights, Haugh units and the incidence of blood spots for each of the seven periods followed a similar pattern; consequently, mean results for only 165 d., 277 d., 390 d., and 490 d. are presented in Table 5. Dietary phosphorus level had no significant (P>0.05) effects on egg weight, blood spots or Haugh units after 225 d. but did have an unexplained effect (P<0.05) on Haugh units at 165 days. Walter and Aitken (1962), Singsen et al. (1962), Hurwitz and Bornstein (1963), Crowley et al. (1963), Hunt and Chancey (1970) and Davidson and Boyne (1970) have previously found dietary phosphorus to have little effect on egg weight. Although strain had a profound effect upon egg weight there was no strain x phosphorus level interactions associated with this variable. There were several strain effects on interior egg quality as measured by Haugh units but the only interaction with dietary phosphorus level was small and occurred at 165 days. The incidence of blood spots varied (P<0.05) between strains at 390 d., the difference being largely among the 3-way strain crosses. There was a strain x dietary phosphorus level interaction (P<0.05) at 165 d. which was primarily attributable to variation among the 2-way strain crosses. A similar interaction between dietary phosphorus and the 3-way strain crosses explains the strain X diet interaction at 277 days. The results of this experiment indicate that S.C.W.L. hens reared and housed in wire cages probably have dietary phosphorus requirements below those listed by the A.R.C. and the N.A.S.-N.R.C. An available phosphorus (inorganic + 50% phytate phosphorus) level calculated to be 0.40% but found to be 0.45% proved to be just as satisfactory as higher dietary levels. The low incidence of strain X
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ment means (60 g.) was small. Both Walter and Aitken (1962) and Hurwitz and Bornstein (1963) have found dietary phosphorus level to affect weight gain during the laying period. Strain had a highly significant (P<0.005) effect on body weight at 497 d. but there was no significant (P>.05) phosphorus level X strain interactions. The body weights of the various strains span the range likely to be found under practical conditions. The effects of strain on body weight are in agreement with those observed by Sibbald and Gowe (1977) on birds drawn from the same populations. Sexual maturity, expressed as age at first egg (A.F.E.), egg production and mortality were not affected (P>0.05) by the level of dietary phosphorus. Summers et al. (1976), Davidson and Boyne (1970), Hunt and Chancey (1970), Crowley et al. (1963) and Walter and Aitken (1962) also found that egg production was not affected by dietary phosphorus levels of 0.15 to 0.63% available or 0.01 to 0.56% inorganic phosphorus; whereas, Ademosun and Kalango (1973), Hurwitz and Bornstein (1963) and Singsen et al. (1962) found that decreasing phosphorus levels from 0.55% to 0.15% available or 0.34% to 0 inorganic phosphorus resulted in lower egg production. The mortality data (Table 3) agree with the results of Walter and Aitken (1962) but not with those of Crowley et al. (1963) and Singsen et al. (1962) who observed lower mortality when dietary phosphorus levels were decreased.
1225
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diet interactions suggests t h a t t h e findings could be applied with confidence u n d e r practical conditions. ACKNOWLEDGEMENTS
REFERENCES Ademosun, A. A., and I. O. Kalango, 1973. Effect of calcium anrd phosphorus levels on the performances of layers in Nigeria. 1. Egg production, egg shell quality, feed intake and body weight. Poultry Sci. 52:1383-1392. Agricultural Research Council (London), 1975. The Nutrient Requirements of Farm Livestock. I. Poultry. Association of Official Agricultural Chemists, 1965. Official Methods of Analysis, 10 ed. Washington, DC. Bayley, H. S., D. Arthur, G. H. Bowmann, J. Pos and R. G. Thomson, 1975. Influence of dietary phosphorus level on growth and bone development in boars and gilts. J. Anim. Sci. 40:864-870. Crowley, T. A., A. A. Kurnick and B. L. Reid, 1963. Dietary phosphorus for laying hens. Poultry Sci. 42:758-765. Davidson, J., and A. W. Boyne, 1970. The calcium and
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The a u t h o r s wish t o t h a n k L. Asselstine for his capable assistance with t h e data files, t o R. W. Bougie, R. T. Poirier and R. A. Arcand for their technical assistance and t o K. Hilson, Drs. A. J. McAllister and W. Lentz for assistance with t h e statistical analyses and t o Dr. I. Motzok, D e p a r t m e n t of Nutrition, University of Guelph for his advice o n t h e d e t e r m i n a t i o n of p h y t a t e p h o s p h o r u s . T h e chemical analyses of feed samples were performed b y t h e staff of t h e Chemical and Biological Research Institute, Agriculture Canada.
phosphorus requirements of laying hens. Br. J. Nutr. 11:231-240. Harvey, W. R., 1960. Least squares analysis of data with unequal subclass numbers. United States Dept. Agric. Pub. A.R.S. 2 0 - 8 . Hunt, J. R., and H. W. R. Chancey, 1970. Influence of dietary phosphorus on shell quality. Br. Poultry Sci. 11:259-267. Hurwitz, S., and S. Bornstein, 1963. The effect of calcium and phosphorus in the diet of laying hens on egg production and shell quality. Israel J. Agric. Res. 13:147-154. McCance, R. A., and E. M. Widdowran, 1937. CCCXX. P h y t i n in human nutrition. Biochem. J. 29:2694-2699. National Academy of Sciences—National Research Council, 1971. Nutrient Requirements of Domestic Animals. I. Nutrient requirements of poultry, 6 ed. Washington, DC. Oshima, M., T. G. Taylor and A. Williams, 1964. Variations in the concentration phytic acid in the blood of the domestic fowl. Biochem. J. 92:42-46. Sibbald, I. R., and R. S. Gowe, 1977. Effects of insoluble grit on the productive performance of ten White Leghorn strains. Br. Poultry Sci. In press. Sibbald, I. R., and R. M. G. Hamilton, 1977. The effect of dietary phosphorus levels and strain of bird on apparent metabolizable energy content of a laying hen diet. Poultry Sci. 56:378-380. Singsen, E. P., A. H. Spandorf, L. D. Matterson, J. A. Serafin and J. J. Tlustohowicz, 1962. Phosphorus in the nutrition of the adult hen. 1. Minimum p h o s p h o r u s r e q u i r e m e n t s . P o u l t r y Sci. 41:1401-1414. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., Toronto, Canada. Summers, J. D., R. Grandhi and S. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-^13. Walter, E. D., and J. R. Aitken, 1962. Phosphorus requirements of laying hens confined to cages. Poultry Sci. 4 1 : 3 8 6 - 3 9 0 .