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Posthatch Carbohydrate Feeding and Subsequent Performance of Turkey Poults1
Posthatch Carbohydrate Feeding and Subsequent Performance of Turkey Poults1 W. E. DONALDSON, 2 C. E. BREWER, P. R. FERKET, and V. L. CHRISTENSEN Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 (Received for publication June 3, 1991)
1992 Poultry Science 71:12»-132
INTRODUCTION The National Research Council (NRC, 1984) lists the protein requirement of turkeys through 4 wk of age as 28% of a diet containing 2,800 kcal ME/kg. The bulk of the protein in commercial diets in the United States is supplied by soybean meal, which contains relatively little carbohydrate (30%) of poor availability (40%) compared with starch (Adolph and Kao, 1934). As the protein level of a diet is increased by addition of soybean meal, there is a corresponding decrease of
The use of trade names in this publication implies neither endorsement by the North Carolina Agricultural Research Service of the products named nor criticism of similar products not named. To whom correspondence should be addressed.
carbohydrate because the soybean meal replaces cereal grains such as corn. Recent work showed that raising the carbohydrate level concomitant with lowering the protein level of feed fed to poults for the first 24 h posthatch increased blood glucose values and lowered hepatic glucose-6-phosphatase activity (Donaldson and Christensen, 1991). Glucose-6-phosphatase is a gluconeogenic enzyme whose activity declines when carbohydrate is consumed (Donaldson, 1973). Thus, it appears that increased dietary carbohydrate intake may aid the poult to make the transition from a lipid-based embryonic metabolism to a glucose-based neonatal metabolism. Although aiding that transition could be beneficial, consumption of low-protein diets during the neonatal period could compromise subsequent performance. Donaldson a n d
128
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ABSTRACT In two floor pen trials, day-old poults were fed a low-protein (18.6%) diet for the first 24 or 48 h compared with control poults fed a 28% protein diet. Beyond these initial treatments, all poults were treated identically and were fed the normal progression of starter, grower, and finisher diets to market weight. The treatments did not alter market age body weight or feed conversion. Early mortality and feed intake during the first 48 h were unaffected by the treatments. Feeding the low-protein diet for 24 h enhanced liver glycogen reserves compared with the control. In a battery cage trial, diets containing 50,33, or 15% available carbohydrate (20,28, or 35% crude protein, respectively) were fed for 24 h posthatch. The diets had no effect on blood glucose level, but liver glycogen concentration increased with increasing dietary carbohydrate. The results clearly indicate that carbohydrate metabolism is altered by posthatch dietary carbohydrate level. The results also suggest that the dietary protein requirement during the first 24 or 48 h posthatch may not be as high as it is currently thought to be. (Key words: carbohydrate level, newly hatched poults, liver glycogen, crude protein, early poult mortality)
129
CARBOHYDRATE INTAKE OF POULTS
Christensen (1991) also suggested that higher carbohydrate intakes may enhance glycogen reserves in the poult. The experiments reported in the present study were designed to assess the effect of varying dietary carbohydrate and protein levels for turkey poults during the first 24 or 48 h of feeding on glycogen reserves and on performance to market weight.
MATERIALS AND METHODS
RESULTS In Experiment 1 (Table 2), feeding the low-protein (18.6%) diet for the first 24 or 48 h after poult placement had no effect on body weights or feed conversion of either males or females at market age or on combined early mortality (7 days of age) compared with feeding the 28% protein diet (CONTROL). Likewise in Experiment 2 (Table 3), in which only males were used, body weight and feed conversion at market age and early mortality (14 days) were unaffected by the protein level fed for the first 24 h after placement in any of the three strains tested. However, the body weights of the Nicholas turkeys were significantly higher than those of the Hybrid and British United turkeys at 16 wk of age (P<.01).
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Two experiments were conducted in floor pens at the North Carolina State University Turkey Research Unit. In Experiment 1, 20 male, day-old Nicholas turkeys were allotted to each of 24 pens (5.9 m 2 ) and 30 female, day-old Nicholas turkeys were allotted to each of 24 additional identical pens. Eight pens of each sex were randomly assigned to each of three treatments for a total of 48 pens. The treatments were 1) CONTROL, fed the National Research Council (1984) recommended protein level of 28.0% throughout the starting period of the experiment; 2) LP-24, fed an 18.6% protein diet for the first 24 h and 28.0% protein for the remainder of the starting period; and 3) LP-48, fed an 18.6% protein diet for the first 48 h and 28.0% protein for the remainder of the starting period. There were no experimental variables other than the protein levels fed during the initial 48 h. The compositions of the two starter diets are shown in Table 1. Females were grown to 15 wk and males to 18 wk of age. In Experiment 2, 25 male, day-old poults were allotted to each of 48 pens (9.7 m 2 ). There were 16 pens each of Nicholas, British United Turkey, and Hybrid poults. Eight pens of each strain were treated as the CONTROL (see Experiment 1) and the remaining eight pens were treated as LP24. Thus, the only variable other than strain was protein level fed during the first 24 h. The birds were grown to 16 wk of age. Eight additional British United Turkey poults fed the 28.0% protein diet and eight fed the 18.6% protein diet were killed by decapitation after 24 h of feeding. Hepatic glycogen was measured in each poult by the method of Dreiling et al. (1987).
In both experiments, standard brooding and rearing practices were employed (Donaldson and Ward, 1988). Average pen body weights and feed consumption were determined at 15 wk (females) and 18 wk (males) in Experiment 1. Pen feed consumption was measured also at 48 h for CONTROL and LP-48 and at 24 and 48 h for LP-24. In Experiment 2, pen body weights and feed consumption were measured at 16 wk. Pen feed consumption was measured also at 24 h. Deaths were recorded as they occurred through 7 days (Experiment 1) and 14 days (Experiment 2). A third experiment was conducted in electrically heated (37 C) battery cages with raised wire floors. Diets containing 20, 28, or 35% crude protein (50, 33, and 15% available carbohydrate) were fed separately to three groups of male, Nicholas, day-old, poults (10 per diet) and are shown in Table 1. Hepatic glycogen was measured in each poult (see above) 24 h after feed was made available as was blood glucose (Donaldson and Christensen, 1991). Statistical analyses were by analysis of variance and t test (Snedecor and Cochran, 1967) and, where appropriate, by a multiple range test (Duncan, 1955). The analyses were made using the General Linear Models procedures of base SAS® software (Helwig and Council, 1979). Percentages were subjected to arc sine transformation before analysis.
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DONALDSON ET AL.
TABLE 1. Composition of the starting diets used in the floor pen trials (Experiments 1 and 2) and the battery trial (Experiment 3) Floor pens Normalprotein diet
Ingredients and analyses
Lowprotein diet
15%
Available carbohydrate 33% 50%
- (% of diet) 6.92
26.18
45.14
71.50
57.20
41.40
.28 220 1.44 .40 5.16
.22 2.20 1.44 .40 5.16
.16 2.20 1.44 .40 5.16
2.00 .10 10.00
2.00 .10 5.10
2.00 .10 1.00
63.60 21.10 8.00 .07 2.23 1.90 .20 .10 .10 2.50 .20 20.2 6.2 3,420
35.0 10.0 2,888
28.0 5.1 2,809
20.2 2.0 2,837
18.6 5.8
1 Solka-floc, James River Corp., Berlin, N H 03570. S u p p l i e d the following per kilogram of feed: vitamin A palmitate, 13,200 IU; cholecalciferol, 4,000 ICU; DL-o-tocopherol acetate, 66 IU; menadione, 4 mg; thiamine mononitrate, 4 mg; riboflavin, 13.2 mg; d-calcium pantothenate, 22 mg; niacin, 110 mg; pyridoxine HCl, 7.9 mg; d-biotin, 253 jig; folic acid, 22 mg; vitamin B ^ 39.6 ug.
S u p p l i e d the following per kilogram of feed: vitamin A palmitate, 4,400 IU; cholecalciferol, 900 ICU; DLa-tocopherol acetate, 22 IU; menadione, 1.1 mg; thiamine mononitrate, 2.75 mg; riboflavin, 5.5 mg; d-calcium pantothenate, 15.4; niacin, 70 mg; pyridoxine HCl, 4.5 mg; d-biotin, 330 ug; choline chloride, 2,200 mg; folic acid, 1 mg; vitamin B12, 19.8 ug. S u p p l i e d in milligrams per kilogram of feed: Cu (as cupric sulfate), 8; I (as potassium iodate), .4; Fe (as ferric citrate), 110; Mn (as manganous sulfate), 77; Se (as sodium selenite), 2; Zn (as zinc carbonate), 60.
TABLE 2. Effects of feeding a low-protein starting diet for the first 24 or 48 h on market weight, feed conversion, and first 7-day mortality in male (18 wk) and female (15 wk) Nicholas turkeys (Experiment l ) 1 Feed conversion (feedrgain)
Body weight Treatment^
Male
Female
Male
flrt-1
Control LP-24 LP-48
12.1 ± 5 11.8 ± .5 12.1 ± .6
7.5 ± .1 7.6 ± .1 7.6 ± .1
2.71 ± .4 2.59 ± .3 2.63 ± .3
Female ftr-rl vg-g'
7-day combined mortality
(%) 2.48 ± .3 2.46 ± 2 2.44 ± .3
15 1.3 1.0
*Each value is the x ± SEM for the survivors of eight groups of 20 male or eight groups of 30 female Nicholas turkeys. •*The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for either the first 24 (LP-24) or the first 48 (LP-48) h, and the 28% protein diet was fed thereafter throughout the starting period.
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Corn starch Yellow corn, ground 41.68 Soybean meal (48.5% CP) 43.90 Poultry meal (60% CP) 8.00 DL-methionine .17 Dicalcium phosphate (21% Cal, 18.5% P) 2.23 Limestone 1.90 Salt .20 1 Nonnutritive bulk Vitamin p r e m b r .10 Vitamin premix 3 Trace mineral premix .10 Refined cottonseed oil Poultry fat 152 Choline chloride, 70% 20 Calculated analysis Protein, % 29.5 Fat, % 4.7 ME, kcal/kg 2,859 Actual analysis Protein, % 28.0 Ether extract, % 4.3
Battery
131
CARBOHYDRATE INTAKE OF POULTS TABLE 3. Effects of feeding a low-protein starting diet for the first 24 h on market weight (16 wk), feed conversion, and first 14-day mortality in male turkeys (Experiment 2) 1 Treatment2
;„3 Strain'
Body weight
Feed conversion (feed:gain)
14-day mortality
(kg) (%) (g:g) 10.5 ± 2 2.42 ± 2 .5 10.6 ± .1 2.40 ± 2 .5 9.7 ± .1 2.39 ± 2 1.0 H 10.1 ± .1 2.38 ± .3 .5 B 9.9 ± .1 2.38 ±2 1.0 10.0 ± .1 2.42 ±2 5 J Each value is the x ± SEM for the survivors of eight groups of 25 male turkeys. ^The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for the first 24 h (LP-24) and the 28% protein diet was fed thereafter throughout the starting period. 3 N = Nicholas; H = Hybrid; and B = British United Turkeys. Control LP-24 Control LP-24 Control LP-24
N
DISCUSSION The present studies extend the original observations (Donaldson and Christensen, 1991) that carbohydrate metabolism is affected by dietary level of available carbohydrate. The results reported herein suggest that both British United (Experiment 2) and Nicholas (Experiment 3) turkeys respond to higher dietary carbohydrate levels by significant enhancement of glycogen reserves. The lack of a carbohydrate effect on blood glucose in Nicholas turkeys (Table 5, Experiment 3) is consistent with the earlier report in which British United Turkey, but not Nicholas, poults exhibited higher plasma glucose levels as dietary carbohydrate level was increased. The fact that poults can utilize, for the first 24 or 48 h, a dietary protein level
TABLE 4. Effects of feeding a low-protein starting diet on 48-h feed consumption of Nicholas poults (Experiment 1) and 24-h hepatic glycogen in British United Turkey poults (Experiment 2) in floor pens Treatment1
48-h feed intake (Experiment 1)
Control LP-24 LP-48
(g per bird) 10.6 ± .6 11.8 ± .7 12.1 ± .6
Glycogen (Experiment 2)3 (mg/g liver) 78 ± 18 118 ±14
(mg per liver) 197 ± 40 334 ± 47*
*The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for either the first 24 (LP-24) or the first 48 (LP-48) h, and the 28% protein diet was fed thereafter. 2 Each value is the x ± SEM for eight groups of 30 male plus eight groups of 30 female Nicholas poults. ^ach value is the x ± SEM for eight British United Turkey poults. Significantly different from control (P<.05).
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Table 4 shows that there were no significant effects of treatment on total feed consumption during the first 48 h after placement in Experiment 1. However, because the low-protein diet contained considerably more corn and less soybean meal than the control diet, presumably carbohydrate intake was higher with the low-protein diet. The validity of that assumption is borne out by the fact that total liver glycogen (Experiment 2) was higher in British United Turkey poults fed the low-protein diet for 24 h. The results of the battery trial (Experiment 3) are shown in Table 5. Increasing the dietary available carbohydrate from 15 to 50% had no effect on blood glucose 24 h postplacement. However, there were significant (P<.05) increases of hepatic glycogen as dietary available carbohydrate was increased.
132
DONALDSON ET AL. TABLE 5. Effects of varying dietary carbohydrate on blood glucose and hepatic glycogen Nicholas day-old poults reared in battery cages for 24 h (Experiment 3) 1
Available carbohydrate^
Diet
Blood glucose
(% available) 50 33 15
(% protein) 20 28 35
(mg/dL) 274 ± 7* 257*10* 269 * 6 a
Hepatic glycogen (mg/g liver) 275 ± 2 2 a 129 ± 19b 70 ± 9°
(mg per liver) 634 ± 7 9 a 290 ± 5 4 b 159 ± 24 b
a_c
Values in the same column with no common superscripts are significantly different (PS.05). Each value is the x ± SEM for 10 poults. 2 Available carbohydrate in corn starch was assumed to be 100% and available carbohydrate in soybean meal was assumed to be 12% (Adolph and Kao, 1934).
ACKNOWLEDGMENTS The authors express their thanks to the North Carolina Poultry Federation and the Institute of Nutrition of the University of North Carolina for financial support and to C. Strickland, S. Knowles, and L. Nicholson for technical assistance.
REFERENCES Adolph, W. A., and H. C. Kao, 1934. The biological availability of soybean carbohydrate. J. Nutr. 7: 395-406. Donaldson, W. E., 1973. Glucose stimulation of fatty acid desaturation in liver of newly-hatched chicks. Biochim. Biophys. Acta 316:8-12. Donaldson, W. E., and V. L. Christensen, 1991. Dietary carbohydrate level and glucose metabolism in turkey poults. Comp. Biochem. Physiol. 98A:347-350. Donaldson, W. E., and J. B. Ward, 1988. Influence of soybean lecithin and corn lecithin additions to dietary fat on metabolizable energy content of chick diets. Nutr. Rep. Int. 38:691-695. Dreiling, C. E., D. E. Brown, L. Casale, and L. Kelly, 1987. Muscle glycogen: Comparison of iodine binding and enzyme digestion assays and application to meat samples. Meat Sci. 20: 167-177. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Helwig, J. T., and K. A. Council, 1979. SAS® User's Guide. SAS Institute Inc., Cary, NC. Kummero, V. E., J. E. Jones, and C. B. Loadholt, 1971. Lysine and total sulfur amino acid requirements of turkey poults, one day to three weeks. Poultry Sci. 50:752-758. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Sann, L., 1990. Neonatal hypoglycemia. Biol. Neonate 58(Suppl. 1):16-21. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods. 6th ed. Iowa State University Press, Ames, LA.
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considerably lower than the NRC (1984) recommendation of 28% for starting diets without affecting subsequent growth was surprising. However, when reports on which the NRC recommendation is based (e.g., Kummero et ah, 1971) are perused, it becomes evident that body weights (other than initial) were not measured prior to 1 wk of age. Hence, an apparent lower protein requirement during the first 24 to 48 h of feeding would be missed. It is clear from the results reported here that feeding low-protein diets for 24 to 48 h postplacement does no harm. The poulf s apparent ability to tolerate reduced protein levels for the first few days raises intriguing questions. Can high protein levels during the first few days be harmful? Is a high carbohydrate intake beneficial? Newly hatched chicks and poults are heavily dependent u p o n gluconeogenesis for provision of glucose prior to feeding (Donaldson, 1973; Donaldson and Christensen, 1991). Thus, if poults are held for long periods or heavily stressed prior to placement, the requirements for glucose could exceed gluconeogenic capacity. Neonatal hypoglycemia in humans can result when gluconeogenic capacity is insufficient (Sann, 1990). Recurrent hypoglycemic episodes can lead to brain damage; if such were to occur in poults, a variety of afflictions leading to morbidity or mortality could ensue. Early mortality was unaffected in these experiments by feeding the low-protein diet for 24 or 48 h postplacement. However, early mortality was quite low (<2%). Controlled tests in flocks experiencing high early mortality are needed.
1992 Poultry Science 71:12»-132
INTRODUCTION The National Research Council (NRC, 1984) lists the protein requirement of turkeys through 4 wk of age as 28% of a diet containing 2,800 kcal ME/kg. The bulk of the protein in commercial diets in the United States is supplied by soybean meal, which contains relatively little carbohydrate (30%) of poor availability (40%) compared with starch (Adolph and Kao, 1934). As the protein level of a diet is increased by addition of soybean meal, there is a corresponding decrease of
The use of trade names in this publication implies neither endorsement by the North Carolina Agricultural Research Service of the products named nor criticism of similar products not named. To whom correspondence should be addressed.
carbohydrate because the soybean meal replaces cereal grains such as corn. Recent work showed that raising the carbohydrate level concomitant with lowering the protein level of feed fed to poults for the first 24 h posthatch increased blood glucose values and lowered hepatic glucose-6-phosphatase activity (Donaldson and Christensen, 1991). Glucose-6-phosphatase is a gluconeogenic enzyme whose activity declines when carbohydrate is consumed (Donaldson, 1973). Thus, it appears that increased dietary carbohydrate intake may aid the poult to make the transition from a lipid-based embryonic metabolism to a glucose-based neonatal metabolism. Although aiding that transition could be beneficial, consumption of low-protein diets during the neonatal period could compromise subsequent performance. Donaldson a n d
128
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ABSTRACT In two floor pen trials, day-old poults were fed a low-protein (18.6%) diet for the first 24 or 48 h compared with control poults fed a 28% protein diet. Beyond these initial treatments, all poults were treated identically and were fed the normal progression of starter, grower, and finisher diets to market weight. The treatments did not alter market age body weight or feed conversion. Early mortality and feed intake during the first 48 h were unaffected by the treatments. Feeding the low-protein diet for 24 h enhanced liver glycogen reserves compared with the control. In a battery cage trial, diets containing 50,33, or 15% available carbohydrate (20,28, or 35% crude protein, respectively) were fed for 24 h posthatch. The diets had no effect on blood glucose level, but liver glycogen concentration increased with increasing dietary carbohydrate. The results clearly indicate that carbohydrate metabolism is altered by posthatch dietary carbohydrate level. The results also suggest that the dietary protein requirement during the first 24 or 48 h posthatch may not be as high as it is currently thought to be. (Key words: carbohydrate level, newly hatched poults, liver glycogen, crude protein, early poult mortality)
129
CARBOHYDRATE INTAKE OF POULTS
Christensen (1991) also suggested that higher carbohydrate intakes may enhance glycogen reserves in the poult. The experiments reported in the present study were designed to assess the effect of varying dietary carbohydrate and protein levels for turkey poults during the first 24 or 48 h of feeding on glycogen reserves and on performance to market weight.
MATERIALS AND METHODS
RESULTS In Experiment 1 (Table 2), feeding the low-protein (18.6%) diet for the first 24 or 48 h after poult placement had no effect on body weights or feed conversion of either males or females at market age or on combined early mortality (7 days of age) compared with feeding the 28% protein diet (CONTROL). Likewise in Experiment 2 (Table 3), in which only males were used, body weight and feed conversion at market age and early mortality (14 days) were unaffected by the protein level fed for the first 24 h after placement in any of the three strains tested. However, the body weights of the Nicholas turkeys were significantly higher than those of the Hybrid and British United turkeys at 16 wk of age (P<.01).
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Two experiments were conducted in floor pens at the North Carolina State University Turkey Research Unit. In Experiment 1, 20 male, day-old Nicholas turkeys were allotted to each of 24 pens (5.9 m 2 ) and 30 female, day-old Nicholas turkeys were allotted to each of 24 additional identical pens. Eight pens of each sex were randomly assigned to each of three treatments for a total of 48 pens. The treatments were 1) CONTROL, fed the National Research Council (1984) recommended protein level of 28.0% throughout the starting period of the experiment; 2) LP-24, fed an 18.6% protein diet for the first 24 h and 28.0% protein for the remainder of the starting period; and 3) LP-48, fed an 18.6% protein diet for the first 48 h and 28.0% protein for the remainder of the starting period. There were no experimental variables other than the protein levels fed during the initial 48 h. The compositions of the two starter diets are shown in Table 1. Females were grown to 15 wk and males to 18 wk of age. In Experiment 2, 25 male, day-old poults were allotted to each of 48 pens (9.7 m 2 ). There were 16 pens each of Nicholas, British United Turkey, and Hybrid poults. Eight pens of each strain were treated as the CONTROL (see Experiment 1) and the remaining eight pens were treated as LP24. Thus, the only variable other than strain was protein level fed during the first 24 h. The birds were grown to 16 wk of age. Eight additional British United Turkey poults fed the 28.0% protein diet and eight fed the 18.6% protein diet were killed by decapitation after 24 h of feeding. Hepatic glycogen was measured in each poult by the method of Dreiling et al. (1987).
In both experiments, standard brooding and rearing practices were employed (Donaldson and Ward, 1988). Average pen body weights and feed consumption were determined at 15 wk (females) and 18 wk (males) in Experiment 1. Pen feed consumption was measured also at 48 h for CONTROL and LP-48 and at 24 and 48 h for LP-24. In Experiment 2, pen body weights and feed consumption were measured at 16 wk. Pen feed consumption was measured also at 24 h. Deaths were recorded as they occurred through 7 days (Experiment 1) and 14 days (Experiment 2). A third experiment was conducted in electrically heated (37 C) battery cages with raised wire floors. Diets containing 20, 28, or 35% crude protein (50, 33, and 15% available carbohydrate) were fed separately to three groups of male, Nicholas, day-old, poults (10 per diet) and are shown in Table 1. Hepatic glycogen was measured in each poult (see above) 24 h after feed was made available as was blood glucose (Donaldson and Christensen, 1991). Statistical analyses were by analysis of variance and t test (Snedecor and Cochran, 1967) and, where appropriate, by a multiple range test (Duncan, 1955). The analyses were made using the General Linear Models procedures of base SAS® software (Helwig and Council, 1979). Percentages were subjected to arc sine transformation before analysis.
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DONALDSON ET AL.
TABLE 1. Composition of the starting diets used in the floor pen trials (Experiments 1 and 2) and the battery trial (Experiment 3) Floor pens Normalprotein diet
Ingredients and analyses
Lowprotein diet
15%
Available carbohydrate 33% 50%
- (% of diet) 6.92
26.18
45.14
71.50
57.20
41.40
.28 220 1.44 .40 5.16
.22 2.20 1.44 .40 5.16
.16 2.20 1.44 .40 5.16
2.00 .10 10.00
2.00 .10 5.10
2.00 .10 1.00
63.60 21.10 8.00 .07 2.23 1.90 .20 .10 .10 2.50 .20 20.2 6.2 3,420
35.0 10.0 2,888
28.0 5.1 2,809
20.2 2.0 2,837
18.6 5.8
1 Solka-floc, James River Corp., Berlin, N H 03570. S u p p l i e d the following per kilogram of feed: vitamin A palmitate, 13,200 IU; cholecalciferol, 4,000 ICU; DL-o-tocopherol acetate, 66 IU; menadione, 4 mg; thiamine mononitrate, 4 mg; riboflavin, 13.2 mg; d-calcium pantothenate, 22 mg; niacin, 110 mg; pyridoxine HCl, 7.9 mg; d-biotin, 253 jig; folic acid, 22 mg; vitamin B ^ 39.6 ug.
S u p p l i e d the following per kilogram of feed: vitamin A palmitate, 4,400 IU; cholecalciferol, 900 ICU; DLa-tocopherol acetate, 22 IU; menadione, 1.1 mg; thiamine mononitrate, 2.75 mg; riboflavin, 5.5 mg; d-calcium pantothenate, 15.4; niacin, 70 mg; pyridoxine HCl, 4.5 mg; d-biotin, 330 ug; choline chloride, 2,200 mg; folic acid, 1 mg; vitamin B12, 19.8 ug. S u p p l i e d in milligrams per kilogram of feed: Cu (as cupric sulfate), 8; I (as potassium iodate), .4; Fe (as ferric citrate), 110; Mn (as manganous sulfate), 77; Se (as sodium selenite), 2; Zn (as zinc carbonate), 60.
TABLE 2. Effects of feeding a low-protein starting diet for the first 24 or 48 h on market weight, feed conversion, and first 7-day mortality in male (18 wk) and female (15 wk) Nicholas turkeys (Experiment l ) 1 Feed conversion (feedrgain)
Body weight Treatment^
Male
Female
Male
flrt-1
Control LP-24 LP-48
12.1 ± 5 11.8 ± .5 12.1 ± .6
7.5 ± .1 7.6 ± .1 7.6 ± .1
2.71 ± .4 2.59 ± .3 2.63 ± .3
Female ftr-rl vg-g'
7-day combined mortality
(%) 2.48 ± .3 2.46 ± 2 2.44 ± .3
15 1.3 1.0
*Each value is the x ± SEM for the survivors of eight groups of 20 male or eight groups of 30 female Nicholas turkeys. •*The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for either the first 24 (LP-24) or the first 48 (LP-48) h, and the 28% protein diet was fed thereafter throughout the starting period.
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Corn starch Yellow corn, ground 41.68 Soybean meal (48.5% CP) 43.90 Poultry meal (60% CP) 8.00 DL-methionine .17 Dicalcium phosphate (21% Cal, 18.5% P) 2.23 Limestone 1.90 Salt .20 1 Nonnutritive bulk Vitamin p r e m b r .10 Vitamin premix 3 Trace mineral premix .10 Refined cottonseed oil Poultry fat 152 Choline chloride, 70% 20 Calculated analysis Protein, % 29.5 Fat, % 4.7 ME, kcal/kg 2,859 Actual analysis Protein, % 28.0 Ether extract, % 4.3
Battery
131
CARBOHYDRATE INTAKE OF POULTS TABLE 3. Effects of feeding a low-protein starting diet for the first 24 h on market weight (16 wk), feed conversion, and first 14-day mortality in male turkeys (Experiment 2) 1 Treatment2
;„3 Strain'
Body weight
Feed conversion (feed:gain)
14-day mortality
(kg) (%) (g:g) 10.5 ± 2 2.42 ± 2 .5 10.6 ± .1 2.40 ± 2 .5 9.7 ± .1 2.39 ± 2 1.0 H 10.1 ± .1 2.38 ± .3 .5 B 9.9 ± .1 2.38 ±2 1.0 10.0 ± .1 2.42 ±2 5 J Each value is the x ± SEM for the survivors of eight groups of 25 male turkeys. ^The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for the first 24 h (LP-24) and the 28% protein diet was fed thereafter throughout the starting period. 3 N = Nicholas; H = Hybrid; and B = British United Turkeys. Control LP-24 Control LP-24 Control LP-24
N
DISCUSSION The present studies extend the original observations (Donaldson and Christensen, 1991) that carbohydrate metabolism is affected by dietary level of available carbohydrate. The results reported herein suggest that both British United (Experiment 2) and Nicholas (Experiment 3) turkeys respond to higher dietary carbohydrate levels by significant enhancement of glycogen reserves. The lack of a carbohydrate effect on blood glucose in Nicholas turkeys (Table 5, Experiment 3) is consistent with the earlier report in which British United Turkey, but not Nicholas, poults exhibited higher plasma glucose levels as dietary carbohydrate level was increased. The fact that poults can utilize, for the first 24 or 48 h, a dietary protein level
TABLE 4. Effects of feeding a low-protein starting diet on 48-h feed consumption of Nicholas poults (Experiment 1) and 24-h hepatic glycogen in British United Turkey poults (Experiment 2) in floor pens Treatment1
48-h feed intake (Experiment 1)
Control LP-24 LP-48
(g per bird) 10.6 ± .6 11.8 ± .7 12.1 ± .6
Glycogen (Experiment 2)3 (mg/g liver) 78 ± 18 118 ±14
(mg per liver) 197 ± 40 334 ± 47*
*The control diet contained 28.0% protein and the low-protein (LP) diet contained 18.6% protein. The LP diet was fed for either the first 24 (LP-24) or the first 48 (LP-48) h, and the 28% protein diet was fed thereafter. 2 Each value is the x ± SEM for eight groups of 30 male plus eight groups of 30 female Nicholas poults. ^ach value is the x ± SEM for eight British United Turkey poults. Significantly different from control (P<.05).
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Table 4 shows that there were no significant effects of treatment on total feed consumption during the first 48 h after placement in Experiment 1. However, because the low-protein diet contained considerably more corn and less soybean meal than the control diet, presumably carbohydrate intake was higher with the low-protein diet. The validity of that assumption is borne out by the fact that total liver glycogen (Experiment 2) was higher in British United Turkey poults fed the low-protein diet for 24 h. The results of the battery trial (Experiment 3) are shown in Table 5. Increasing the dietary available carbohydrate from 15 to 50% had no effect on blood glucose 24 h postplacement. However, there were significant (P<.05) increases of hepatic glycogen as dietary available carbohydrate was increased.
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DONALDSON ET AL. TABLE 5. Effects of varying dietary carbohydrate on blood glucose and hepatic glycogen Nicholas day-old poults reared in battery cages for 24 h (Experiment 3) 1
Available carbohydrate^
Diet
Blood glucose
(% available) 50 33 15
(% protein) 20 28 35
(mg/dL) 274 ± 7* 257*10* 269 * 6 a
Hepatic glycogen (mg/g liver) 275 ± 2 2 a 129 ± 19b 70 ± 9°
(mg per liver) 634 ± 7 9 a 290 ± 5 4 b 159 ± 24 b
a_c
Values in the same column with no common superscripts are significantly different (PS.05). Each value is the x ± SEM for 10 poults. 2 Available carbohydrate in corn starch was assumed to be 100% and available carbohydrate in soybean meal was assumed to be 12% (Adolph and Kao, 1934).
ACKNOWLEDGMENTS The authors express their thanks to the North Carolina Poultry Federation and the Institute of Nutrition of the University of North Carolina for financial support and to C. Strickland, S. Knowles, and L. Nicholson for technical assistance.
REFERENCES Adolph, W. A., and H. C. Kao, 1934. The biological availability of soybean carbohydrate. J. Nutr. 7: 395-406. Donaldson, W. E., 1973. Glucose stimulation of fatty acid desaturation in liver of newly-hatched chicks. Biochim. Biophys. Acta 316:8-12. Donaldson, W. E., and V. L. Christensen, 1991. Dietary carbohydrate level and glucose metabolism in turkey poults. Comp. Biochem. Physiol. 98A:347-350. Donaldson, W. E., and J. B. Ward, 1988. Influence of soybean lecithin and corn lecithin additions to dietary fat on metabolizable energy content of chick diets. Nutr. Rep. Int. 38:691-695. Dreiling, C. E., D. E. Brown, L. Casale, and L. Kelly, 1987. Muscle glycogen: Comparison of iodine binding and enzyme digestion assays and application to meat samples. Meat Sci. 20: 167-177. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Helwig, J. T., and K. A. Council, 1979. SAS® User's Guide. SAS Institute Inc., Cary, NC. Kummero, V. E., J. E. Jones, and C. B. Loadholt, 1971. Lysine and total sulfur amino acid requirements of turkey poults, one day to three weeks. Poultry Sci. 50:752-758. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Sann, L., 1990. Neonatal hypoglycemia. Biol. Neonate 58(Suppl. 1):16-21. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods. 6th ed. Iowa State University Press, Ames, LA.
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considerably lower than the NRC (1984) recommendation of 28% for starting diets without affecting subsequent growth was surprising. However, when reports on which the NRC recommendation is based (e.g., Kummero et ah, 1971) are perused, it becomes evident that body weights (other than initial) were not measured prior to 1 wk of age. Hence, an apparent lower protein requirement during the first 24 to 48 h of feeding would be missed. It is clear from the results reported here that feeding low-protein diets for 24 to 48 h postplacement does no harm. The poulf s apparent ability to tolerate reduced protein levels for the first few days raises intriguing questions. Can high protein levels during the first few days be harmful? Is a high carbohydrate intake beneficial? Newly hatched chicks and poults are heavily dependent u p o n gluconeogenesis for provision of glucose prior to feeding (Donaldson, 1973; Donaldson and Christensen, 1991). Thus, if poults are held for long periods or heavily stressed prior to placement, the requirements for glucose could exceed gluconeogenic capacity. Neonatal hypoglycemia in humans can result when gluconeogenic capacity is insufficient (Sann, 1990). Recurrent hypoglycemic episodes can lead to brain damage; if such were to occur in poults, a variety of afflictions leading to morbidity or mortality could ensue. Early mortality was unaffected in these experiments by feeding the low-protein diet for 24 or 48 h postplacement. However, early mortality was quite low (<2%). Controlled tests in flocks experiencing high early mortality are needed.