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Use of Single-Stage Low Protein Diets for Growing Leghorn Pullets
Use of Single-Stage Low Protein Diets for Growing Leghorn Pullets S. LEESON and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph, Guelpb, Ontario, Canada NIG 2W1 (Received for publication December 10, 1981)
1982 Poultry Science 61:1684-1691 INTRODUCTION
The nutrient requirements of the growing White Leghorn pullet are not well defined, since production goals are ultimately associated with subsequent laying performance. Two common parameters used to assess pullet quality are body weight and uniformity of weight at sexual maturity. These goals can, however, be achieved by two completely different growing programs. Thus, a conventional step-down program involves a dietary series providing sequential reductions in protein content with increasing age (Summers and Leeson, 1976). Contrary to this, Leeson and Summers (1979) indicated that the same production goals could be achieved with a reverse-protein program involving sequential increases in diet protein content with age. These two diametrically opposed concepts suggest that the pullet is flexible in growth and sexual development. Considering the protein intakes • achieved with these two programs, it is calculated that a comparable intake should result through use of a single diet containing some 14% crude protein (CP). There are few recent reports on the use of such low protein programs, and the majority
of these do not involve the entire 0 to 20-week growing period (Summers et al., 1972; Kim and McGinnis, 1976). Adequate pullet development with such a single-stage rearing program would be of interest to the industry because of its simplicity. Two experiments were therefore designed to observe the pullets' response to such a singlestage program throughout growth. In the first trial, amino acid balance of the low-protein diet was considered and compared with conventional and reverse-protein standards. In a second trial, diets differing in energy level were used to note the birds's response to differences in feed intake and protein consumption.
MATERIALS AND METHODS Experiment 1. Day-old White Leghorn chicks of a commercial strain were weighed, wing-banded, and randomly distributed to rearing cages maintained in a controlled environment room. Eleven chicks were placed in each cage with 14 such replicate cages being assigned to each dietary treatment. These diet treatments are shown in Table 1. With the
1684
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ABSTRACT Two experiments were conducted in which growing White Leghorn pullets were fed single-stage 14% CP diets from 0 to 19 weeks. In the first trial, diet treatments were 1) conventional step-down protein, 2) reverse-protein, 3) 14% CP single-stage with methionine and lysine adjusted to 2 and 5% of CP, respectively, 4) as per 3 to 12 weeks followed by 14% CP with no amino acid constraints to 19 weeks. Each treatment was tested with 14 replicated cages each of 11 commercial strain Leghorn pullets. Single-stage 14% CP diets reduced pullet weight to 16 weeks relative to conventionally fed birds, although after this time no significant (PX05) effect was observed. Pullets fed the reverse-protein diets were significantly (P<.01) smaller than birds from all other treatments. During a subsequent 52-week laying period, rearing treatment had no significant effect on egg production, egg weight, shell deformation, feed intake, or Haugh units. A second trial was conducted to note the effect of energy level on the birds' response to low-protein diets. Diets of 14.4% CP were formulated to provide either 2610 or 3164 kcal ME/kg. A third treatment allowed for self-selection of two diets providing concentrated sources of protein or energy. Each treatment was tested with nine replicate cages of 10 commercial strain White Leghorn pullets. Dietary energy had little effect on pullet development. Although birds offered the low-energy diets consistently consumed more protein, diet had no effect on body weight or carcass composition at 18 weeks. The data indicate that single-stage low-protein diets are suitable for growing pullets to maturity. Compared to a conventional step-down protein program, the single-stage 14% CP diet does not control body weight but does give comparable laying performance, albeit at reduced protein intake during rearing. The simplicity of the program is discussed relative to industry needs. (Key words: single-stage, low protein, reverse-protein, pullets, step-down)
LOW PROTEIN DIETS FOR PULLETS
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At the end of the growing period, birds were transferred to individual laying cages maintained in a controlled environment room. Fourteen hours light was provided from 18 to 71 weeks of age. Each of the four rearing treatments was represented by 10 replicate groups of 14 individually caged birds. All birds were fed a crumbled corn-soybean based diet (8, Table 1). Egg production and feed intake were recorded for each 28 day period of production. Eggs collected during the last 2 days of each period were weighed and egg shell deformation measured (Summers et ah, 1976). Experiment 2. To observe the effect of diet energy level on the birds' response to lowprotein diets, single-stage growing diets of 14.4% CP were formulated to provide either low (2610 kcal ME/kg) or high (3164 kcal ME/kg) levels of energy (diets 1 and 2, Table 2). To gain more information on energy intake and pullet growth, a third treatment provided birds with a free choice of concentrated sources of energy and protein (split-diets 3 and 4, Table 2). These two diets were provided ad libitum in separate sections of the feed trough. All diets were offered as a mash, with each treatment being tested with nine replicate cages of 10 commercial strain White Leghorn chicks. Management procedures were as described for Experiment 1. Bird weight and feed intake were measured at 2-week intervals to 18 weeks of age. At 18 weeks, 5 randomly selected birds per
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conventional program (treatment 1) diets 1, 2, and 3 were offered from 0 to 8 weeks, 8 to 12 weeks, and 12 to 19 weeks, respectively, and with the reverse-protein program (treatment 2), diets 4, 5, and 6 were offered from 0 to 12 weeks, 12 to 16 weeks, and 16 to 19 weeks, respectively. In treatment 3, diet 7 (Table 1) was offered from 0 to 19 weeks of age and contained supplemental methionine and lysine to ensure levels of 2 and 5% CP, respectively. For treatment 4, diet 7 was offered only to 12" weeks of age, at which time diet 8, without added methionine or lysine level, was offered through to 19 weeks. All diets were in mash form and offered ad libitum. Conventional brooding and management procedures were used throughout rearing. Twenty-four hours light was provided to 3 days at which time daily photoperiod was reduced to 8 hr at 10 lx intensity. Body weight and feed intake were measured at 8, 12, 16, and 19 weeks of age.
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LEESON AND SUMMERS TABLE 2. Diet composition and calculated analysis (Experiment 2) Low energy low protein 1
Calculated analysis Crude protein (%) Metabolizable energy (kcal/kg) 1
75.73 17.00
11.00 63.75 18.00 1.00 2.00 1.25 .25 .75 .05
Split diets 4
3
94.54 94.45
3.00
1.00
2.0
2.0
1.0 2.0
1.25
1.25
1.25
.25 .75 .02
.25 .75
.25 .75 .30
.21
1.95 100.00
100.00
14.4 2610
100.00
14.4 3164
8.1
3215
100.00 45.3 2490
See Leeson and Summers (1979).
treatment were used for carcass analysis. After partial freezing, entire carcasses were passed twice through a Hobart meat grinder. Representative subsamples were then freeze-dried prior to analysis of Kjeldahl nitrogen and ether-extractable fat. RESULTS AND DISCUSSION In Experiment 1, low-protein treatments resulted in a significant (P<.01) reduction in body weight to 16 weeks of age relative to control birds receiving the higher protein starter diet (Table 3). At all ages, birds offered the reverse-protein program were significantly
(P<.01) smaller in body weight relative to all other treatments. At 16 weeks of age, 14% CP single-stage diets had no effect on body weight relative to the control group; also, body weight was not influenced by supplementation of methionine and lysine (Table 3). Birds on the two low-protein treatments (3 and 4) consumed similar quantities of protein and energy throughout the growth period (Table 4). Energy intake for these birds was similar to that seen with die control group, although protein intake was significantly less (P<.01) when birds were fed these single-stage diets (Table 4). Pullets reared on the reverseprotein diets had protein intakes commensurate
TABLE 3. Diet effect on body weight (g) and mortality (%) (Experiment 1) Weeks of age Treatment
1. Conventional 2. Reverse-protein 3. 14% CP 4. 14% CP - no amino acid constraint a 1
-
'
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8
12
16
19
570c 367a 489b 517b
946c 689a 891b 865b
1222c 1061a 1187b 1187b
1504b 1370a 1484b 1478b
Mortality 1
1.4 2.9 5.0 4.3
' Within columns, means followed by different superscript letters are significantly different (P<.01). No significant difference (P>.05).
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Ground corn Soybean meal (48%) Ground barley Ground oats Animal-vegetable fat Dicalcium phosphate Limestone Iodized salt Mineral-vitamin mix 1 DL-methionine L-lysine Alpha floe cellulose
High energy low protein 2
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with diet protein specifications; to 12 weeks of age, when they were consuming a 12% CP starter diet, protein consumption was significantly less than that observed with other treatments. However, when higher protein content grower diets were fed from 12 to 19 weeks, these same birds ate the greatest quantity of protein (Table 4). Over the entire rearing period, significantly less protein was consumed by the reverse-protein pullets, whereas birds fed either of the two low-protein diets consumed less protein than did conventionally fed pullets. Rearing treatments had no significant (P>.05) effect on mean production parameters measured throughout a 52-week laying period (Table 5). Use of reverse-protein diets resulted in significantly reduced egg size during the first 4 weeks of production. Contrary to this latter effect, birds reared on the single-stage lowprotein diets produced significantly (P>.05) larger eggs relative to control birds during the first 4 weeks of lay. After this time no significant differences in egg size were observed. Rearing treatment had no effect on final bird weight, because all groups were not significantly (P<.05) different to a mean of 1900 g.
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Results from trial 2 indicated that energy level had little effect on the pullets response to single-stage low-protein rearing diets. Thus intake of high vs. low energy diets resulted in a significantly increased body weight only at four weeks of age (Table 6). Pullets offered the two split-diets were consistently smaller in body size than birds fed the low-protein diets (Table 6). Consumption of the high energy diet generally resulted in increased energy intake compared to that seen with birds on the low-energy diet, although this effect was significant only to 8 weeks of age. Up to 6 weeks of age splitdiet fed birds consumed more energy than did the low-energy group, but from 4 to 8 weeks these same birds consumed less energy relative to the high-energy fed pullets (Table 7). Birds eating the low-energy diet (treatment 1) consistently consumed more protein than birds on the comparable high energy diet (treatment 1 vs. 2, Table 8). There was no consistent pattern of protein intake for pullets fed the split-diets relative to that observed with the alternative treatments. Rearing diets had no significant (P>.05) effect on carcass protein or fat content at 18 weeks of age (Table 9). Relative to the control situation in Experiment 1, birds reared on the 14.5% CP diets throughout were comparable in body weight at
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o
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1
134 133 131
2
NS
^g;
**
** **
**
83lb 802b 729 a
660b 656b 608a
46 3 b 462b 424 a
266 a 280 b 257 c
**P<.01.
*P<.05.
10
8
6
4
Weeks of age
' ' c Within columns, means followed by different superscript letters are significantly different.
1. Low protein-low energy 2. Low protein-high energy 3. Split diets
a
NS
NS 1
57.0 56.1 57.1 56.9
Egg weight
NS
111.0 112.9 112.7 112.8
Feed inta
**
993b 953b 874 a
12
TABLE 6. Effect of rearing diet on body weight (g) (Experiment 2)
75.1 74.8 75.2 75.6
(% Hen-day basis)
(days)
147.6 151.8 148.2 149.0
Egg production
Age at first egg
NS, no significant difference (P>.05).
Conventional Reverse-protein 14% CP 14% CP - no amino acid constraint
Treatment
1. 2. 3. 4.
Treatment
TABLE 5. Effect of rearing diet on laying performance through 52 weeks of producti
rom http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
2138b 2250c 2044a
1651a 1835c 1744b
963a 1212D 1223b
1. Low protein-low energy 2. Low protein-high energy 3. Split diets 2200 2294 2190
8-10
98 b 89 a 84 a
57 a 59 a 69 b
1. Low protein-low energy 2. Low protein-high energy 3. Split diets
127 b 109a 110a
6-8
130c 112b 98 a
8-10
143b 117a 107a
10-12
Weeks of age
**P<.01.
*P<.05.
' ' c Within columns, means followed by different superscript letters are significantly different.
4-6
2-4
Treatment
a
2404 2405 2366
10-12
172b 141a 162b
12-14
TABLE 8. Effect of rearing diet on protein intake and overall feed intake (g) (E
a,b,c,Within columns, means followed by different superscript letters are significantly different (P<.01).
6-8
4-6
2-4
Treatment
(Experime
Weeks of age
TABLE 7. Effect of rearing diet on energy intake (kcal/bird)
from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
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LEESON AND SUMMERS TABLE 9. Rearing diet effect on carcass protein and fat contents (Experiment 2)
Treatment
Dry matter (DM)
Crude protein
Fat
(%) 1. Low protein-low energy 2. Low protein-high energy 3. Split diets 1
40.6 + 2.8 1 43.6+ 5.0 39.0 ± 3.2
55.4 ± 6.4 50.9 ± 7.8 51.1 ± 5.1
35.5 ± 7.9 41.2 + 6.1 31.1 ± 6.8
Mean + standard deviation, n = 5.
Although protein consumption of pullets on the 14% CP diets was significantly reduced, performance including egg size was not adversely affected. This suggests that conventionally fed birds consume excessive quantities of protein during the rearing period. As previously indicated, there are few recent reports on the use of single-stage low-protein diets for pullets. Earlier work has indicated the potential of this program, although general conclusions gravitated toward step-down protein diets because these former diets resulted in
too marked a reduction in early body size. Thus Sunde and Bird (1959) indicated that 15% CP diets throughout rearing had no adverse effect on body weight at maturity or subsequent laying performance. These workers did, however, indicate a substantial increase in mortality rate with the low-protein single-phase diet. Lillie and Denton (1966) also indicated no adverse effect on laying performance when birds were fed a 12% CP diet throughout rearing. More recently, Summers et al. (1972) used 14% CP pullet diets to 8 weeks of age and observed comparable reducations in body weight and nutrient intake as recorded in these trials. However, contrary to results seen in Table 3, Summers et al. (1972) reported that feeding 14% CP to 8 weeks of age had a carryover effect on body weight at 20 weeks irrespective of the 8 to 20-week feeding program. Energy level of the low-protein diet in Experiment 2 had little effect on pullet performance. Thus, even though protein intake was reduced with the high energy diet, body weight at 18 weeks was not affected, although this was associated with a nonsignificant (P>.05) increase in carcass protein content at 18 weeks of age. These data confirm the observations of Turk et al. (1961). Pullets reared on the high vs. low energy diet consumed more energy to 8 weeks of age, although after this time energy intake was not significantly affected. The growing pullet seems adept at controlling its energy intake, and this is confirmed by the comparable energy intake pattern observed with birds offered a choice of diets in the split-diet program. These data confirm the observations of Leeson and Summers (1981) that suggest that the limiting factor in controlling pullet growth rate is the bird's voluntary limit to energy intake. Similarly, Wolf et al. (1969) previously indicated that dietary energy and protein level have little
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maturity and exhibited similar performance characteristics during a subsequent 52-week laying cycle; this performance was, however, achieved with significantly less protein intake during rearing. In developing the 12% CP starter diet of the reverse-protein program, Leeson and Summers (1979) indicated that amino acid balance was critical, but that adequate growth and condition could be realized when methionine and lysine represented 2 and 5% of CP, respectively. These same specifications were used in these trials up to 12 weeks of age, although after this time amino acid supplementation of the 14% CP diet did not appear to be necessary (treatment 4, Tables 3 to 5). Kim and McGinnis (1976) also suggested that -supplementation of these same amino acids was not essential with low-protein pullet diets from 12 to 20 weeks of age. It was interesting that the 14% CP diets did not limit early growth as did the 12% CP starter used in the reverseprotein series. The 14% CP diets reduced growth rate up to 12 weeks of age relative to the control-fed birds, yet it appeared that this slower growth rate was not sufficient to affect "mature" body weight at 18 weeks. Leeson (unpublished observation) has recorded a similar situation in broiler pullets, because a critical minimum level of protein in the diet was shown essential for body weight control.
LOW PROTEIN DIETS FOR PULLETS
ACKNOWLEDGMENTS This w o r k was s u p p o r t e d b y t h e O n t a r i o Ministry of Agriculture and F o o d and t h e National Sciences and Engineering Council of Canada.
REFERENCES Kim, S. M., and J. McGinnis, 1976. Effect of levels and sources of dietary protein in pullet grower diet on subsequent performance. Poultry Sci. 55:895-905. Leeson, S., and J. D. Summers, 1979. Step-up protein
diets for growing pullets. Poultry Sci. 58:681 — 686. Leeson, S., and J. D. Summers, 1981. Effect of rearing diet on performance of early maturing pullets. Can. J. Anim. Sci. 61:743-749. Lillie, R. J., and C. A. Denton, 1966. Effect of nutrient restriction on White Leghorns in the grower and subsequent layer period. Poultry Sci. 45:810-818. Sunde, M. L., and H. R. Bird, 1959. The protein requirements of growing pullets. Poultry Sci. 38:48-55. Summers, J. D., R. Grandhi, and S. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-413. Summers, J. D. and S. Leeson, 1976. Poultry Nutrition Handbook. Publ. Ontario Minnesota Agric. Food., Toronto, Ontario. Summers, J. D., W. F. Pepper, and E. T. Moran, 1972. Low protein starting diets and their effects on subsequent pullet performance. Can. J. Anim. Sci. 52:761-766. Turk, D. E., W. G. Hoekstra, H. R. Bird, and M. L. Sunde, 1961. The effect of dietary protein and energy levels on the growth of replacement pullets. Poultry Sci. 40:708-716. Wolf, J. D„ E. W. Gleaves, L. V. Tonkinson, R. H. Thayer, and R. D. Morrison, 1969. Dietary protein, energy and volume in pullet diets as related to growing and laying performance. Poultry Sci. 48:559-574.
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
effect on energy intake, and t h a t diet volume was t h e only factor significantly influencing energy c o n s u m p t i o n up to m a t u r i t y . These d a t a indicate t h a t single-stage, lowp r o t e i n diets are suitable for growing Leghorn pullets t o m a t u r i t y . C o m p a r e d t o a conventional step-down p r o t e i n regimen this singlestage 14% CP diet does n o t c o n t r o l b o d y weight, b u t it d o e s give c o m p a r a b l e laying p e r f o r m a n c e albeit at reduced p r o t e i n intake during rearing. T h e practical advantage of such a single-stage program is evident for its simplicity.
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1982 Poultry Science 61:1684-1691 INTRODUCTION
The nutrient requirements of the growing White Leghorn pullet are not well defined, since production goals are ultimately associated with subsequent laying performance. Two common parameters used to assess pullet quality are body weight and uniformity of weight at sexual maturity. These goals can, however, be achieved by two completely different growing programs. Thus, a conventional step-down program involves a dietary series providing sequential reductions in protein content with increasing age (Summers and Leeson, 1976). Contrary to this, Leeson and Summers (1979) indicated that the same production goals could be achieved with a reverse-protein program involving sequential increases in diet protein content with age. These two diametrically opposed concepts suggest that the pullet is flexible in growth and sexual development. Considering the protein intakes • achieved with these two programs, it is calculated that a comparable intake should result through use of a single diet containing some 14% crude protein (CP). There are few recent reports on the use of such low protein programs, and the majority
of these do not involve the entire 0 to 20-week growing period (Summers et al., 1972; Kim and McGinnis, 1976). Adequate pullet development with such a single-stage rearing program would be of interest to the industry because of its simplicity. Two experiments were therefore designed to observe the pullets' response to such a singlestage program throughout growth. In the first trial, amino acid balance of the low-protein diet was considered and compared with conventional and reverse-protein standards. In a second trial, diets differing in energy level were used to note the birds's response to differences in feed intake and protein consumption.
MATERIALS AND METHODS Experiment 1. Day-old White Leghorn chicks of a commercial strain were weighed, wing-banded, and randomly distributed to rearing cages maintained in a controlled environment room. Eleven chicks were placed in each cage with 14 such replicate cages being assigned to each dietary treatment. These diet treatments are shown in Table 1. With the
1684
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
ABSTRACT Two experiments were conducted in which growing White Leghorn pullets were fed single-stage 14% CP diets from 0 to 19 weeks. In the first trial, diet treatments were 1) conventional step-down protein, 2) reverse-protein, 3) 14% CP single-stage with methionine and lysine adjusted to 2 and 5% of CP, respectively, 4) as per 3 to 12 weeks followed by 14% CP with no amino acid constraints to 19 weeks. Each treatment was tested with 14 replicated cages each of 11 commercial strain Leghorn pullets. Single-stage 14% CP diets reduced pullet weight to 16 weeks relative to conventionally fed birds, although after this time no significant (PX05) effect was observed. Pullets fed the reverse-protein diets were significantly (P<.01) smaller than birds from all other treatments. During a subsequent 52-week laying period, rearing treatment had no significant effect on egg production, egg weight, shell deformation, feed intake, or Haugh units. A second trial was conducted to note the effect of energy level on the birds' response to low-protein diets. Diets of 14.4% CP were formulated to provide either 2610 or 3164 kcal ME/kg. A third treatment allowed for self-selection of two diets providing concentrated sources of protein or energy. Each treatment was tested with nine replicate cages of 10 commercial strain White Leghorn pullets. Dietary energy had little effect on pullet development. Although birds offered the low-energy diets consistently consumed more protein, diet had no effect on body weight or carcass composition at 18 weeks. The data indicate that single-stage low-protein diets are suitable for growing pullets to maturity. Compared to a conventional step-down protein program, the single-stage 14% CP diet does not control body weight but does give comparable laying performance, albeit at reduced protein intake during rearing. The simplicity of the program is discussed relative to industry needs. (Key words: single-stage, low protein, reverse-protein, pullets, step-down)
LOW PROTEIN DIETS FOR PULLETS
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At the end of the growing period, birds were transferred to individual laying cages maintained in a controlled environment room. Fourteen hours light was provided from 18 to 71 weeks of age. Each of the four rearing treatments was represented by 10 replicate groups of 14 individually caged birds. All birds were fed a crumbled corn-soybean based diet (8, Table 1). Egg production and feed intake were recorded for each 28 day period of production. Eggs collected during the last 2 days of each period were weighed and egg shell deformation measured (Summers et ah, 1976). Experiment 2. To observe the effect of diet energy level on the birds' response to lowprotein diets, single-stage growing diets of 14.4% CP were formulated to provide either low (2610 kcal ME/kg) or high (3164 kcal ME/kg) levels of energy (diets 1 and 2, Table 2). To gain more information on energy intake and pullet growth, a third treatment provided birds with a free choice of concentrated sources of energy and protein (split-diets 3 and 4, Table 2). These two diets were provided ad libitum in separate sections of the feed trough. All diets were offered as a mash, with each treatment being tested with nine replicate cages of 10 commercial strain White Leghorn chicks. Management procedures were as described for Experiment 1. Bird weight and feed intake were measured at 2-week intervals to 18 weeks of age. At 18 weeks, 5 randomly selected birds per
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
conventional program (treatment 1) diets 1, 2, and 3 were offered from 0 to 8 weeks, 8 to 12 weeks, and 12 to 19 weeks, respectively, and with the reverse-protein program (treatment 2), diets 4, 5, and 6 were offered from 0 to 12 weeks, 12 to 16 weeks, and 16 to 19 weeks, respectively. In treatment 3, diet 7 (Table 1) was offered from 0 to 19 weeks of age and contained supplemental methionine and lysine to ensure levels of 2 and 5% CP, respectively. For treatment 4, diet 7 was offered only to 12" weeks of age, at which time diet 8, without added methionine or lysine level, was offered through to 19 weeks. All diets were in mash form and offered ad libitum. Conventional brooding and management procedures were used throughout rearing. Twenty-four hours light was provided to 3 days at which time daily photoperiod was reduced to 8 hr at 10 lx intensity. Body weight and feed intake were measured at 8, 12, 16, and 19 weeks of age.
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LEESON AND SUMMERS TABLE 2. Diet composition and calculated analysis (Experiment 2) Low energy low protein 1
Calculated analysis Crude protein (%) Metabolizable energy (kcal/kg) 1
75.73 17.00
11.00 63.75 18.00 1.00 2.00 1.25 .25 .75 .05
Split diets 4
3
94.54 94.45
3.00
1.00
2.0
2.0
1.0 2.0
1.25
1.25
1.25
.25 .75 .02
.25 .75
.25 .75 .30
.21
1.95 100.00
100.00
14.4 2610
100.00
14.4 3164
8.1
3215
100.00 45.3 2490
See Leeson and Summers (1979).
treatment were used for carcass analysis. After partial freezing, entire carcasses were passed twice through a Hobart meat grinder. Representative subsamples were then freeze-dried prior to analysis of Kjeldahl nitrogen and ether-extractable fat. RESULTS AND DISCUSSION In Experiment 1, low-protein treatments resulted in a significant (P<.01) reduction in body weight to 16 weeks of age relative to control birds receiving the higher protein starter diet (Table 3). At all ages, birds offered the reverse-protein program were significantly
(P<.01) smaller in body weight relative to all other treatments. At 16 weeks of age, 14% CP single-stage diets had no effect on body weight relative to the control group; also, body weight was not influenced by supplementation of methionine and lysine (Table 3). Birds on the two low-protein treatments (3 and 4) consumed similar quantities of protein and energy throughout the growth period (Table 4). Energy intake for these birds was similar to that seen with die control group, although protein intake was significantly less (P<.01) when birds were fed these single-stage diets (Table 4). Pullets reared on the reverseprotein diets had protein intakes commensurate
TABLE 3. Diet effect on body weight (g) and mortality (%) (Experiment 1) Weeks of age Treatment
1. Conventional 2. Reverse-protein 3. 14% CP 4. 14% CP - no amino acid constraint a 1
-
'
,c
8
12
16
19
570c 367a 489b 517b
946c 689a 891b 865b
1222c 1061a 1187b 1187b
1504b 1370a 1484b 1478b
Mortality 1
1.4 2.9 5.0 4.3
' Within columns, means followed by different superscript letters are significantly different (P<.01). No significant difference (P>.05).
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
Ground corn Soybean meal (48%) Ground barley Ground oats Animal-vegetable fat Dicalcium phosphate Limestone Iodized salt Mineral-vitamin mix 1 DL-methionine L-lysine Alpha floe cellulose
High energy low protein 2
LOW PROTEIN DIETS FOR PULLETS
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with diet protein specifications; to 12 weeks of age, when they were consuming a 12% CP starter diet, protein consumption was significantly less than that observed with other treatments. However, when higher protein content grower diets were fed from 12 to 19 weeks, these same birds ate the greatest quantity of protein (Table 4). Over the entire rearing period, significantly less protein was consumed by the reverse-protein pullets, whereas birds fed either of the two low-protein diets consumed less protein than did conventionally fed pullets. Rearing treatments had no significant (P>.05) effect on mean production parameters measured throughout a 52-week laying period (Table 5). Use of reverse-protein diets resulted in significantly reduced egg size during the first 4 weeks of production. Contrary to this latter effect, birds reared on the single-stage lowprotein diets produced significantly (P>.05) larger eggs relative to control birds during the first 4 weeks of lay. After this time no significant differences in egg size were observed. Rearing treatment had no effect on final bird weight, because all groups were not significantly (P<.05) different to a mean of 1900 g.
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Results from trial 2 indicated that energy level had little effect on the pullets response to single-stage low-protein rearing diets. Thus intake of high vs. low energy diets resulted in a significantly increased body weight only at four weeks of age (Table 6). Pullets offered the two split-diets were consistently smaller in body size than birds fed the low-protein diets (Table 6). Consumption of the high energy diet generally resulted in increased energy intake compared to that seen with birds on the low-energy diet, although this effect was significant only to 8 weeks of age. Up to 6 weeks of age splitdiet fed birds consumed more energy than did the low-energy group, but from 4 to 8 weeks these same birds consumed less energy relative to the high-energy fed pullets (Table 7). Birds eating the low-energy diet (treatment 1) consistently consumed more protein than birds on the comparable high energy diet (treatment 1 vs. 2, Table 8). There was no consistent pattern of protein intake for pullets fed the split-diets relative to that observed with the alternative treatments. Rearing diets had no significant (P>.05) effect on carcass protein or fat content at 18 weeks of age (Table 9). Relative to the control situation in Experiment 1, birds reared on the 14.5% CP diets throughout were comparable in body weight at
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
NO < S
o
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1
134 133 131
2
NS
^g;
**
** **
**
83lb 802b 729 a
660b 656b 608a
46 3 b 462b 424 a
266 a 280 b 257 c
**P<.01.
*P<.05.
10
8
6
4
Weeks of age
' ' c Within columns, means followed by different superscript letters are significantly different.
1. Low protein-low energy 2. Low protein-high energy 3. Split diets
a
NS
NS 1
57.0 56.1 57.1 56.9
Egg weight
NS
111.0 112.9 112.7 112.8
Feed inta
**
993b 953b 874 a
12
TABLE 6. Effect of rearing diet on body weight (g) (Experiment 2)
75.1 74.8 75.2 75.6
(% Hen-day basis)
(days)
147.6 151.8 148.2 149.0
Egg production
Age at first egg
NS, no significant difference (P>.05).
Conventional Reverse-protein 14% CP 14% CP - no amino acid constraint
Treatment
1. 2. 3. 4.
Treatment
TABLE 5. Effect of rearing diet on laying performance through 52 weeks of producti
rom http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
2138b 2250c 2044a
1651a 1835c 1744b
963a 1212D 1223b
1. Low protein-low energy 2. Low protein-high energy 3. Split diets 2200 2294 2190
8-10
98 b 89 a 84 a
57 a 59 a 69 b
1. Low protein-low energy 2. Low protein-high energy 3. Split diets
127 b 109a 110a
6-8
130c 112b 98 a
8-10
143b 117a 107a
10-12
Weeks of age
**P<.01.
*P<.05.
' ' c Within columns, means followed by different superscript letters are significantly different.
4-6
2-4
Treatment
a
2404 2405 2366
10-12
172b 141a 162b
12-14
TABLE 8. Effect of rearing diet on protein intake and overall feed intake (g) (E
a,b,c,Within columns, means followed by different superscript letters are significantly different (P<.01).
6-8
4-6
2-4
Treatment
(Experime
Weeks of age
TABLE 7. Effect of rearing diet on energy intake (kcal/bird)
from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
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LEESON AND SUMMERS TABLE 9. Rearing diet effect on carcass protein and fat contents (Experiment 2)
Treatment
Dry matter (DM)
Crude protein
Fat
(%) 1. Low protein-low energy 2. Low protein-high energy 3. Split diets 1
40.6 + 2.8 1 43.6+ 5.0 39.0 ± 3.2
55.4 ± 6.4 50.9 ± 7.8 51.1 ± 5.1
35.5 ± 7.9 41.2 + 6.1 31.1 ± 6.8
Mean + standard deviation, n = 5.
Although protein consumption of pullets on the 14% CP diets was significantly reduced, performance including egg size was not adversely affected. This suggests that conventionally fed birds consume excessive quantities of protein during the rearing period. As previously indicated, there are few recent reports on the use of single-stage low-protein diets for pullets. Earlier work has indicated the potential of this program, although general conclusions gravitated toward step-down protein diets because these former diets resulted in
too marked a reduction in early body size. Thus Sunde and Bird (1959) indicated that 15% CP diets throughout rearing had no adverse effect on body weight at maturity or subsequent laying performance. These workers did, however, indicate a substantial increase in mortality rate with the low-protein single-phase diet. Lillie and Denton (1966) also indicated no adverse effect on laying performance when birds were fed a 12% CP diet throughout rearing. More recently, Summers et al. (1972) used 14% CP pullet diets to 8 weeks of age and observed comparable reducations in body weight and nutrient intake as recorded in these trials. However, contrary to results seen in Table 3, Summers et al. (1972) reported that feeding 14% CP to 8 weeks of age had a carryover effect on body weight at 20 weeks irrespective of the 8 to 20-week feeding program. Energy level of the low-protein diet in Experiment 2 had little effect on pullet performance. Thus, even though protein intake was reduced with the high energy diet, body weight at 18 weeks was not affected, although this was associated with a nonsignificant (P>.05) increase in carcass protein content at 18 weeks of age. These data confirm the observations of Turk et al. (1961). Pullets reared on the high vs. low energy diet consumed more energy to 8 weeks of age, although after this time energy intake was not significantly affected. The growing pullet seems adept at controlling its energy intake, and this is confirmed by the comparable energy intake pattern observed with birds offered a choice of diets in the split-diet program. These data confirm the observations of Leeson and Summers (1981) that suggest that the limiting factor in controlling pullet growth rate is the bird's voluntary limit to energy intake. Similarly, Wolf et al. (1969) previously indicated that dietary energy and protein level have little
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
maturity and exhibited similar performance characteristics during a subsequent 52-week laying cycle; this performance was, however, achieved with significantly less protein intake during rearing. In developing the 12% CP starter diet of the reverse-protein program, Leeson and Summers (1979) indicated that amino acid balance was critical, but that adequate growth and condition could be realized when methionine and lysine represented 2 and 5% of CP, respectively. These same specifications were used in these trials up to 12 weeks of age, although after this time amino acid supplementation of the 14% CP diet did not appear to be necessary (treatment 4, Tables 3 to 5). Kim and McGinnis (1976) also suggested that -supplementation of these same amino acids was not essential with low-protein pullet diets from 12 to 20 weeks of age. It was interesting that the 14% CP diets did not limit early growth as did the 12% CP starter used in the reverseprotein series. The 14% CP diets reduced growth rate up to 12 weeks of age relative to the control-fed birds, yet it appeared that this slower growth rate was not sufficient to affect "mature" body weight at 18 weeks. Leeson (unpublished observation) has recorded a similar situation in broiler pullets, because a critical minimum level of protein in the diet was shown essential for body weight control.
LOW PROTEIN DIETS FOR PULLETS
ACKNOWLEDGMENTS This w o r k was s u p p o r t e d b y t h e O n t a r i o Ministry of Agriculture and F o o d and t h e National Sciences and Engineering Council of Canada.
REFERENCES Kim, S. M., and J. McGinnis, 1976. Effect of levels and sources of dietary protein in pullet grower diet on subsequent performance. Poultry Sci. 55:895-905. Leeson, S., and J. D. Summers, 1979. Step-up protein
diets for growing pullets. Poultry Sci. 58:681 — 686. Leeson, S., and J. D. Summers, 1981. Effect of rearing diet on performance of early maturing pullets. Can. J. Anim. Sci. 61:743-749. Lillie, R. J., and C. A. Denton, 1966. Effect of nutrient restriction on White Leghorns in the grower and subsequent layer period. Poultry Sci. 45:810-818. Sunde, M. L., and H. R. Bird, 1959. The protein requirements of growing pullets. Poultry Sci. 38:48-55. Summers, J. D., R. Grandhi, and S. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-413. Summers, J. D. and S. Leeson, 1976. Poultry Nutrition Handbook. Publ. Ontario Minnesota Agric. Food., Toronto, Ontario. Summers, J. D., W. F. Pepper, and E. T. Moran, 1972. Low protein starting diets and their effects on subsequent pullet performance. Can. J. Anim. Sci. 52:761-766. Turk, D. E., W. G. Hoekstra, H. R. Bird, and M. L. Sunde, 1961. The effect of dietary protein and energy levels on the growth of replacement pullets. Poultry Sci. 40:708-716. Wolf, J. D„ E. W. Gleaves, L. V. Tonkinson, R. H. Thayer, and R. D. Morrison, 1969. Dietary protein, energy and volume in pullet diets as related to growing and laying performance. Poultry Sci. 48:559-574.
Downloaded from http://ps.oxfordjournals.org/ at Albert R. Mann Library on November 2, 2014
effect on energy intake, and t h a t diet volume was t h e only factor significantly influencing energy c o n s u m p t i o n up to m a t u r i t y . These d a t a indicate t h a t single-stage, lowp r o t e i n diets are suitable for growing Leghorn pullets t o m a t u r i t y . C o m p a r e d t o a conventional step-down p r o t e i n regimen this singlestage 14% CP diet does n o t c o n t r o l b o d y weight, b u t it d o e s give c o m p a r a b l e laying p e r f o r m a n c e albeit at reduced p r o t e i n intake during rearing. T h e practical advantage of such a single-stage program is evident for its simplicity.
1691