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Effects of Recycling Dried Poultry Waste on Young Chicks1
Effects of Recycling Dried Poultry Waste on Young Chicks1 N . TRAKULCHANG AND S. L . BALLOUN
Department of Animal Science, Iowa State University, Ames, Iowa 50010 (Received for publication July 31, 1974)
ABSTRACT Three experimental diets containing 0, 10 and 20% recycled dried poultry waste (DPW) were formulated isocaloric (2950 Kcal./kg.) and equivalent in percentage of true protein (16%), calcium and phosphorus. Each experimental diet was fed to 4 replicate groups kept in wire-floored batteries. Excreta from each group was collected weekly, dried, ground and mixed with the diet to be fed the following week. DPW recycling, at both 10 and 20% dietary levels, significantly depressed weight gain of birds 4 to 8 weeks of age, but feed efficiency was depressed by 20% dietary DPW only. As the numbers of recyclings increased, calcium and magnesium contents of the excreta decreased linearly. Potassium and zinc tended to increase, and other minerals remained constant. Increasing DPW in the diet significantly decreased calcium, phosphorus, and iron in excreta (P,in < 0.01); sodium and potassium were increased significantly (Plin < 0.01), and Cu, Mg, Mn, and Zn were increased significantly (P]in < 0.05). The percentage of 3-nitro-4-hydroxy phenyiarsonic acid retained by the chicks was significantly decreased (P n n < 0.01) by increasing level of DPW in the diet and by recycling. Because recycling DPW increased 3-nitro of the diets fed, however, the absolute amount of the drug retained tended to increase. POULTRY SCIENCE 54: 615-618, 1975
INTRODUCTION
D
RIED poultry waste (DPW) "recycling" studies have been done mostly with laying hens. Ousterhout and Presser (1971) reported that fresh feces recycled through laying hens caused a rapid decrease in egg production. Recycling feces once resulted in a 25% utilization of the total dry matter nutrients of the feces. Analysis of feces indicated constant percentages of dry matter, fiber, ash, calcium, phosphorus, potassium and sodium. Flegal and Dorn (1971) stated that there was a trend towards a slightly increased percentage of calcium and phosphorus in feces when DPW was recycled for 14 cycles. Varghese and Flegal (1972) reported that, after 23 recyclings, the levels of arsonic acid, mercury, copper and zinc were not appreciably altered in the tissues, feces or eggs by recycling DPW from laying hens. No references of DPW recycling in young
1. Journal Paper No. J-7974 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 1932.
chick diets were found in the literature. The reports just cited indicate that calcium, phosphorus and other minerals in DPW either could not be utilized by laying hens or that mineral sources other than DPW in the diet contributed enough minerals for the laying hens so that the hens did not utilize the minerals from DPW. The experiment reported here was conducted to investigate the effects of DPW recycling in the diet of young chicks. EXPERIMENTAL PROCEDURES Three experimental diets (Table 1) were formulated isocaloric (2950 Kcal./kg.) and equivalent in percentage of true protein (16%). DPW was added to the diets at 10 and 20% levels, replacing ground yellow corn and alfalfa meal. Soybean oil was used in diets containing DPW to equalize the energy level and to reduce dustiness. For 4 consecutive weeks, all excreta from each pen were collected and dried weekly at 80° C. for 48 hours, ground and mixed with diets to be fed the following week. Broiler chicks (4 weeks old) were randomly
615
616
N. TRAKULCHANG AND S. L. BALLOUN TABLE 1.—Ration composition
Experimental diets (%) Ingredients Ground corn (9% protein) Soybean meal (49% protein) Alfalfa meal (18% protein) Dicalcium phosphate Ground limestone Micromix' Mineral mix 2 Soybean oil Dried excreta (DPW) 3 Cr 2 0 3 Calculated analysis: True protein (%) Nitrogen (%) M.E., Kcal./kg. Calcium (%) Phosphorus (%) Fiber (%)
69.6 16.4 8.0 2.4 2.3 0.5 0.5
— — 0.3
65.4 16.6 4.0 1.2 1.2 0.5 0.5 0.3 10.0 0.3
59.8 16.3 2.0 0.5 0.5 0.6 20.0 0.3
16.0 16.0 2.8 3.0 2915 2900 1.6 1.6 0.8 0.8 4.3 5.2 'Supplied per kg. of diet: vitamin A, 7,500 I.U.; vitamin D 3 , 1,000 I.C.U.; vitamin E, 10 I.U.; menadione sodium bisulfite, 2.2 mg.; vitamin B 12 , 10 meg.; riboflavin, 5 mg.; choline chloride, 450 mg.; pantothenic acid, 10 mg.; niacin, 25 mg.; methionine, 1,000 mg.; ethoxyquin, 100 mg.; 3-nitro-4-hydroxy phenylarsonic acid, 50 mg. 2 Supplied per kg. of diet: NaCl, 4.4 g.; Mn, 117 mg.; Zn, 50 mg.; Fe, 35 mg.; Cu, 6 mg.; I 2 , 2 mg.; Co, 0.55 mg. 3 Average analysis: true protein, 11%; N x 6.25, 24%. 16.0 2.6 2910 1.6 0.8 3.8
assigned to two 6-deck batteries. Each pen of 6 birds constituted an experimental unit, and each dietary treatment was assigned to 4 pens. The experiment was a randomized complete-block arrangement of treatments in a split-plot design, with numbers of recyclings as subplots. Feed and water were available to the chicks ad libitum throughout the 4-week test period. Mineral contents of excreta were determined by an atomic absorption spectrophotometer, and 3-nitro-4-hydroxy phenylarsonic acid was determined by Salsbury Laboratories, Charles City, Iowa. Statistical analyses of the data were completed according to methods described by Snedecor and Cochran (1967). RESULTS AND DISCUSSION Data in Table 2 indicate that increasing levels of recycled DPW in the diets signifi-
cantly and linearly decreased weight gain of young chicks (P < 0.05). Recycling DPW at the 10% dietary level did not affect feed efficiency, but diets containing 20% DPW caused a 14.3% increase in feed required per unit gain. Calcium and phosphorus contents of recycled DPW were significantly affected by the dietary treatments (Table 3). Calcium in DPW
TABLE 2.—The effects of DPW recycling on weight gain and feed efficiency of broilers 4-8 weeks of age g. feed/ Dietary av. gam treatment g. gain' Basal diet 2.8 a 900 a 10% DPW 864 b 2.8 a 20% DPW 782 c 3.2 b 1 All values represent means of 4replicate groups, 6 birds per group. Values in a column followed by different letters are significantly different (P < 0.05).
617
DRIED POULTRY WASTE FOR CHICKS
TABLE 3.—Structural and homeostatic elements in DPW after recycling'
Elements Structural elements Ca
P
Homeostatic elements Na
K
Dietary treatments
Number of " recyclings 1
2
3
4
0% DPW 10% DPW 20% DPW
4.86 a 3.86 be 1.41 e
Content in excreta (%) 4.27 b 4.94 a 2.57 d 3.51 c 0.56 f 0.70 f
0%DPW 10% DPW 20% DPW
1.87 a 1.67 b 1.31 c
1.96 a 1.57 b 1.25 c
1.87 a 1.63 b 1.33 c
1.89 a 1.75 ab 1.29 c
0%DPW 10% DPW 20% DPW
0.448 a 0.610 c 0.626 b
0.547 b 0.662 c 0.662 c
0.493 ab 0.638 c 0.712 d
0.489 ab 0.475 a 0.565 b
0%DPW 10% DPW 20% DPW
1.313 ab 1.238 a 1.884 f
1.520 d 1.379 be 2.472 g
1.446 c 1.699 e 2.191 fg
1.294 ab 1.702 e 2.758 h
4.10 b 3.01 cd 0.44 f
'All values represent means of 4 replicate groups. Values for each mineral not followed by a common letter are significantly different (P < 0.01). decreased as the levels of recycled DPW in the diets and the numbers of recyclings increased. The linear effect on calcium was significant (P < 0.01), and the quadratic effect was significant (P < 0.05) for both concentration of DPW in the diets and for number of recyclings. As the levels of DPW increased, phosphorus content of the recycled DPW decreased linearly (P < 0.01), but was not affected by the numbers of recyclings. Because the three diets, as formulated at the
beginning of the experiment, were equivalent in calcium and phosphorus, the decreased calcium and phosphorus in DPW from pens fed recycled DPW indicates efficient utilization of these minerals from the DPW. For sodium and potassium concentrations in DPW, the effect of increased DPW in the diet and of recycling was, in general, the opposite of the effect on calcium and phosphorus. Numbers of recyclings did not significantly affect the sodium concentration in the
TABLE 4.—Trace mineral elements in DPW after recycling'
Mg
0%DPW 10% DPW 20% DPW
0.502a 0.565d 0.580d
Number of recyclings 3 2 Percentage in excreta 0.502a 0.500a 0.571d 0.530bc 0.606e 0.627e
Zn
0%DPW 10% DPW 20% DPW
0.031a 0.046ab 0.062bc
0.028a 0.043ab 0.084d
0.027a 0.045ab 0.098d
0.027a 0.038ab 0.092d
Mn
0%DPW 10% DPW 20% DPW
0.041a 0.047ab 0.050b
0.038a 0.044ab 0.050b
0.038a 0.050b 0.058c
0.042a 0.042a 0.053bc
Cu
0%DPW 10% DPW 20% DPW
0.003a 0.004ab 0.005b
0.003a 0.004ab 0.005b
0.004ab 0.004ab 0.005b
0.003a 0.004ab 0.005b
Fe
0% DPW 10% DPW 20% DPW
0.161b 0.143c 0.112d
0.180b 0.134c 0.098d
0.190a 0.138c 0.091d
0.155bc 0.138c 0.093d
Elements
Dietary treatments
1
4 0.489a 0.493a 0.541c
'All values represent means of 4 replicate groups, 6 birds per group. Values for each mineral, not followed by a common letter are significantly different (P < 0.05).
618
N. TRAKULCHANG AND S. L. BALLOUN TABLE 5.—The effects of DPW recycling on 3-nitro-4-hydroxy-phenyIarsonic percentage retention n. . rv treatments
acid in excreta and
Number of recyclings 2 3 P.P.M. in dried excreta 1,2 41.8 a 44.2 a 41.2 a Basal diet 38.5 a 53.4 a 50.0 ab 10% DPW 35.4 a 53.3 a 54.6 a 20% DPW Percentage retained' 73.8 ab 75.2 a 75.9 a Basal diet 70.8 be 74.1 ab 77.5 a 10% DPW 68.2c 68.9 c 73.0 b 20% DPW 'All values represent means of 4 replicate groups. Values (for each criterion) not common letter are significantly different (P < 0.01). 2 We are indebted to Salsbury Laboratories, Charles City, Iowa, for the determinations droxy-phenylarsonic acid in dried excreta. 1
excreta, but DPW in the diet significantly (P|in < 0.01) increased the sodium excreted. The same type effect was observed for potassium; also, numbers of recyclings also significantly (P l i n < 0.01) increased potassium excreted. These effects indicate poor utilization of the sodium and potassium from excreta when the excreta are added to the diet as DPW. All trace mineral elements determined in DPW (Table 4), except iron, increased linearly (P lin < 0.05) as the dietary levels of recycled DPW increased. Iron content of DPW decreased linearly (P lin < 0.01) as the dietary recycled DPW was increased. Number of recyclings caused no consistently significant effects. Dietary levels of DPW and numbers of DPW recyclings (Table 5) significantly affected percentage retention of 3-nitro-4-hydroxy phenylarsonic acid (3-nitro) by chicks, but there were no statistically significant effects on 3-nitro content in dried excreta. Percentage of intake of 3-nitro retained by the chicks fed increasing dietary levels of recycled DPW decreased significantly (P lin < 0.01). The decrease also was significant (P < 0.01) as the numbers of DPW recyclings increased. The results indicated that recycled DPW cannot be used successfully unless the calcium to phosphorus ratio (and content) of the
4 38.3 a 42.9 a 49.1 a 74.6 a 73.6 ab 68.0 c followed by a of 3-nitro-4-hy-
diet is adjusted for each recycling. Because DPW contributed most of the calcium and phosphorus in the 20% recycled DPW diet, any change in the calcium to phosphorus ratio of the recycled DPW also would alter the calcium to phosphorus ratio in the diet. After the first recycling, the calcium to phosphorus ratio was 1:1 for the 20% DPW diet. This ratio decreased linearly to 0.34:1 after the fourth recycling. This may explain why the 20% recycled DPW diet drastically depressed growth. Data in Table 5 indicate that birds tended to retain a constant amount of 3-nitro4-hydroxy phenylarsonic acid, but, during the first 2 weeks of DPW recycling, the birds excreted more and thus retained less of the drug. REFERENCES Flegal, C. J., and D. A. Dorn, 1971. The effects of continually recycling dehydrated poultry wastes (DPW) on the performance of SCWL laying hens— A preliminary report. Michigan State Univ. Agr. Expt. Sta. Res. Rep. 152: 45-48. Ousterhout, L. E., and R. H. Presser, 1971. Increased feces production from hens being fed poultry manure. Poultry Sci. 50: 1614. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. The Iowa State University Press, Ames, Iowa. Varghese, S. K., and C. J. Flegal, 1972. The effects of continuous recycling dried poultry waste in laying hen diets on trace minerals found in various tissues. Poultry Sci. 51: 1882.
Department of Animal Science, Iowa State University, Ames, Iowa 50010 (Received for publication July 31, 1974)
ABSTRACT Three experimental diets containing 0, 10 and 20% recycled dried poultry waste (DPW) were formulated isocaloric (2950 Kcal./kg.) and equivalent in percentage of true protein (16%), calcium and phosphorus. Each experimental diet was fed to 4 replicate groups kept in wire-floored batteries. Excreta from each group was collected weekly, dried, ground and mixed with the diet to be fed the following week. DPW recycling, at both 10 and 20% dietary levels, significantly depressed weight gain of birds 4 to 8 weeks of age, but feed efficiency was depressed by 20% dietary DPW only. As the numbers of recyclings increased, calcium and magnesium contents of the excreta decreased linearly. Potassium and zinc tended to increase, and other minerals remained constant. Increasing DPW in the diet significantly decreased calcium, phosphorus, and iron in excreta (P,in < 0.01); sodium and potassium were increased significantly (Plin < 0.01), and Cu, Mg, Mn, and Zn were increased significantly (P]in < 0.05). The percentage of 3-nitro-4-hydroxy phenyiarsonic acid retained by the chicks was significantly decreased (P n n < 0.01) by increasing level of DPW in the diet and by recycling. Because recycling DPW increased 3-nitro of the diets fed, however, the absolute amount of the drug retained tended to increase. POULTRY SCIENCE 54: 615-618, 1975
INTRODUCTION
D
RIED poultry waste (DPW) "recycling" studies have been done mostly with laying hens. Ousterhout and Presser (1971) reported that fresh feces recycled through laying hens caused a rapid decrease in egg production. Recycling feces once resulted in a 25% utilization of the total dry matter nutrients of the feces. Analysis of feces indicated constant percentages of dry matter, fiber, ash, calcium, phosphorus, potassium and sodium. Flegal and Dorn (1971) stated that there was a trend towards a slightly increased percentage of calcium and phosphorus in feces when DPW was recycled for 14 cycles. Varghese and Flegal (1972) reported that, after 23 recyclings, the levels of arsonic acid, mercury, copper and zinc were not appreciably altered in the tissues, feces or eggs by recycling DPW from laying hens. No references of DPW recycling in young
1. Journal Paper No. J-7974 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 1932.
chick diets were found in the literature. The reports just cited indicate that calcium, phosphorus and other minerals in DPW either could not be utilized by laying hens or that mineral sources other than DPW in the diet contributed enough minerals for the laying hens so that the hens did not utilize the minerals from DPW. The experiment reported here was conducted to investigate the effects of DPW recycling in the diet of young chicks. EXPERIMENTAL PROCEDURES Three experimental diets (Table 1) were formulated isocaloric (2950 Kcal./kg.) and equivalent in percentage of true protein (16%). DPW was added to the diets at 10 and 20% levels, replacing ground yellow corn and alfalfa meal. Soybean oil was used in diets containing DPW to equalize the energy level and to reduce dustiness. For 4 consecutive weeks, all excreta from each pen were collected and dried weekly at 80° C. for 48 hours, ground and mixed with diets to be fed the following week. Broiler chicks (4 weeks old) were randomly
615
616
N. TRAKULCHANG AND S. L. BALLOUN TABLE 1.—Ration composition
Experimental diets (%) Ingredients Ground corn (9% protein) Soybean meal (49% protein) Alfalfa meal (18% protein) Dicalcium phosphate Ground limestone Micromix' Mineral mix 2 Soybean oil Dried excreta (DPW) 3 Cr 2 0 3 Calculated analysis: True protein (%) Nitrogen (%) M.E., Kcal./kg. Calcium (%) Phosphorus (%) Fiber (%)
69.6 16.4 8.0 2.4 2.3 0.5 0.5
— — 0.3
65.4 16.6 4.0 1.2 1.2 0.5 0.5 0.3 10.0 0.3
59.8 16.3 2.0 0.5 0.5 0.6 20.0 0.3
16.0 16.0 2.8 3.0 2915 2900 1.6 1.6 0.8 0.8 4.3 5.2 'Supplied per kg. of diet: vitamin A, 7,500 I.U.; vitamin D 3 , 1,000 I.C.U.; vitamin E, 10 I.U.; menadione sodium bisulfite, 2.2 mg.; vitamin B 12 , 10 meg.; riboflavin, 5 mg.; choline chloride, 450 mg.; pantothenic acid, 10 mg.; niacin, 25 mg.; methionine, 1,000 mg.; ethoxyquin, 100 mg.; 3-nitro-4-hydroxy phenylarsonic acid, 50 mg. 2 Supplied per kg. of diet: NaCl, 4.4 g.; Mn, 117 mg.; Zn, 50 mg.; Fe, 35 mg.; Cu, 6 mg.; I 2 , 2 mg.; Co, 0.55 mg. 3 Average analysis: true protein, 11%; N x 6.25, 24%. 16.0 2.6 2910 1.6 0.8 3.8
assigned to two 6-deck batteries. Each pen of 6 birds constituted an experimental unit, and each dietary treatment was assigned to 4 pens. The experiment was a randomized complete-block arrangement of treatments in a split-plot design, with numbers of recyclings as subplots. Feed and water were available to the chicks ad libitum throughout the 4-week test period. Mineral contents of excreta were determined by an atomic absorption spectrophotometer, and 3-nitro-4-hydroxy phenylarsonic acid was determined by Salsbury Laboratories, Charles City, Iowa. Statistical analyses of the data were completed according to methods described by Snedecor and Cochran (1967). RESULTS AND DISCUSSION Data in Table 2 indicate that increasing levels of recycled DPW in the diets signifi-
cantly and linearly decreased weight gain of young chicks (P < 0.05). Recycling DPW at the 10% dietary level did not affect feed efficiency, but diets containing 20% DPW caused a 14.3% increase in feed required per unit gain. Calcium and phosphorus contents of recycled DPW were significantly affected by the dietary treatments (Table 3). Calcium in DPW
TABLE 2.—The effects of DPW recycling on weight gain and feed efficiency of broilers 4-8 weeks of age g. feed/ Dietary av. gam treatment g. gain' Basal diet 2.8 a 900 a 10% DPW 864 b 2.8 a 20% DPW 782 c 3.2 b 1 All values represent means of 4replicate groups, 6 birds per group. Values in a column followed by different letters are significantly different (P < 0.05).
617
DRIED POULTRY WASTE FOR CHICKS
TABLE 3.—Structural and homeostatic elements in DPW after recycling'
Elements Structural elements Ca
P
Homeostatic elements Na
K
Dietary treatments
Number of " recyclings 1
2
3
4
0% DPW 10% DPW 20% DPW
4.86 a 3.86 be 1.41 e
Content in excreta (%) 4.27 b 4.94 a 2.57 d 3.51 c 0.56 f 0.70 f
0%DPW 10% DPW 20% DPW
1.87 a 1.67 b 1.31 c
1.96 a 1.57 b 1.25 c
1.87 a 1.63 b 1.33 c
1.89 a 1.75 ab 1.29 c
0%DPW 10% DPW 20% DPW
0.448 a 0.610 c 0.626 b
0.547 b 0.662 c 0.662 c
0.493 ab 0.638 c 0.712 d
0.489 ab 0.475 a 0.565 b
0%DPW 10% DPW 20% DPW
1.313 ab 1.238 a 1.884 f
1.520 d 1.379 be 2.472 g
1.446 c 1.699 e 2.191 fg
1.294 ab 1.702 e 2.758 h
4.10 b 3.01 cd 0.44 f
'All values represent means of 4 replicate groups. Values for each mineral not followed by a common letter are significantly different (P < 0.01). decreased as the levels of recycled DPW in the diets and the numbers of recyclings increased. The linear effect on calcium was significant (P < 0.01), and the quadratic effect was significant (P < 0.05) for both concentration of DPW in the diets and for number of recyclings. As the levels of DPW increased, phosphorus content of the recycled DPW decreased linearly (P < 0.01), but was not affected by the numbers of recyclings. Because the three diets, as formulated at the
beginning of the experiment, were equivalent in calcium and phosphorus, the decreased calcium and phosphorus in DPW from pens fed recycled DPW indicates efficient utilization of these minerals from the DPW. For sodium and potassium concentrations in DPW, the effect of increased DPW in the diet and of recycling was, in general, the opposite of the effect on calcium and phosphorus. Numbers of recyclings did not significantly affect the sodium concentration in the
TABLE 4.—Trace mineral elements in DPW after recycling'
Mg
0%DPW 10% DPW 20% DPW
0.502a 0.565d 0.580d
Number of recyclings 3 2 Percentage in excreta 0.502a 0.500a 0.571d 0.530bc 0.606e 0.627e
Zn
0%DPW 10% DPW 20% DPW
0.031a 0.046ab 0.062bc
0.028a 0.043ab 0.084d
0.027a 0.045ab 0.098d
0.027a 0.038ab 0.092d
Mn
0%DPW 10% DPW 20% DPW
0.041a 0.047ab 0.050b
0.038a 0.044ab 0.050b
0.038a 0.050b 0.058c
0.042a 0.042a 0.053bc
Cu
0%DPW 10% DPW 20% DPW
0.003a 0.004ab 0.005b
0.003a 0.004ab 0.005b
0.004ab 0.004ab 0.005b
0.003a 0.004ab 0.005b
Fe
0% DPW 10% DPW 20% DPW
0.161b 0.143c 0.112d
0.180b 0.134c 0.098d
0.190a 0.138c 0.091d
0.155bc 0.138c 0.093d
Elements
Dietary treatments
1
4 0.489a 0.493a 0.541c
'All values represent means of 4 replicate groups, 6 birds per group. Values for each mineral, not followed by a common letter are significantly different (P < 0.05).
618
N. TRAKULCHANG AND S. L. BALLOUN TABLE 5.—The effects of DPW recycling on 3-nitro-4-hydroxy-phenyIarsonic percentage retention n. . rv treatments
acid in excreta and
Number of recyclings 2 3 P.P.M. in dried excreta 1,2 41.8 a 44.2 a 41.2 a Basal diet 38.5 a 53.4 a 50.0 ab 10% DPW 35.4 a 53.3 a 54.6 a 20% DPW Percentage retained' 73.8 ab 75.2 a 75.9 a Basal diet 70.8 be 74.1 ab 77.5 a 10% DPW 68.2c 68.9 c 73.0 b 20% DPW 'All values represent means of 4 replicate groups. Values (for each criterion) not common letter are significantly different (P < 0.01). 2 We are indebted to Salsbury Laboratories, Charles City, Iowa, for the determinations droxy-phenylarsonic acid in dried excreta. 1
excreta, but DPW in the diet significantly (P|in < 0.01) increased the sodium excreted. The same type effect was observed for potassium; also, numbers of recyclings also significantly (P l i n < 0.01) increased potassium excreted. These effects indicate poor utilization of the sodium and potassium from excreta when the excreta are added to the diet as DPW. All trace mineral elements determined in DPW (Table 4), except iron, increased linearly (P lin < 0.05) as the dietary levels of recycled DPW increased. Iron content of DPW decreased linearly (P lin < 0.01) as the dietary recycled DPW was increased. Number of recyclings caused no consistently significant effects. Dietary levels of DPW and numbers of DPW recyclings (Table 5) significantly affected percentage retention of 3-nitro-4-hydroxy phenylarsonic acid (3-nitro) by chicks, but there were no statistically significant effects on 3-nitro content in dried excreta. Percentage of intake of 3-nitro retained by the chicks fed increasing dietary levels of recycled DPW decreased significantly (P lin < 0.01). The decrease also was significant (P < 0.01) as the numbers of DPW recyclings increased. The results indicated that recycled DPW cannot be used successfully unless the calcium to phosphorus ratio (and content) of the
4 38.3 a 42.9 a 49.1 a 74.6 a 73.6 ab 68.0 c followed by a of 3-nitro-4-hy-
diet is adjusted for each recycling. Because DPW contributed most of the calcium and phosphorus in the 20% recycled DPW diet, any change in the calcium to phosphorus ratio of the recycled DPW also would alter the calcium to phosphorus ratio in the diet. After the first recycling, the calcium to phosphorus ratio was 1:1 for the 20% DPW diet. This ratio decreased linearly to 0.34:1 after the fourth recycling. This may explain why the 20% recycled DPW diet drastically depressed growth. Data in Table 5 indicate that birds tended to retain a constant amount of 3-nitro4-hydroxy phenylarsonic acid, but, during the first 2 weeks of DPW recycling, the birds excreted more and thus retained less of the drug. REFERENCES Flegal, C. J., and D. A. Dorn, 1971. The effects of continually recycling dehydrated poultry wastes (DPW) on the performance of SCWL laying hens— A preliminary report. Michigan State Univ. Agr. Expt. Sta. Res. Rep. 152: 45-48. Ousterhout, L. E., and R. H. Presser, 1971. Increased feces production from hens being fed poultry manure. Poultry Sci. 50: 1614. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. The Iowa State University Press, Ames, Iowa. Varghese, S. K., and C. J. Flegal, 1972. The effects of continuous recycling dried poultry waste in laying hen diets on trace minerals found in various tissues. Poultry Sci. 51: 1882.