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Dietary Self-Selection by Turkeys
METABOLISM AND NUTRITION Dietary Self-Selection by Turkeys S. LEESON and J. D. SUMMERS Department of Animal and Poultry Science, University ofGuelph, Guelpb, Ontario, Canada (Received for publication February 8, 1977)
INTRODUCTION A previous report from our laboratory (Summers and Leeson, 1978) described the production characteristics of broiler chickens allowed a degree of dietary self-selection. Although the simultaneous presentation of diets containing concentrated sources of either protein or energy resulted in inferior growth rate, carcass fat content was dramatically increased, especially for the male. While this latter effect is not usually regarded as advantageous with broiler chickens, it is of prime consideration in the production of both broiler and large-type turkeys (Moran, 1977). Since we are unaware of any data pertaining to diet self-selection by turkeys, an experiment was conducted to study such, with particular emphasis on the relationship between energy and protein consumption and carcass composition. Due to the slow initial growth rate of broilers offered these diets, (Summers and Leeson, 1978) it was also decided to compare diet self-selction with a compensatory growth rearing program. MATERIALS AND METHODS Experimental treatments consisted of conventional, self-selection, and compensatory growth rearing programs. Poults on the conventional program received a 28.4% crude protein (CP), 2955 kcal/kg diet at day-of-age, with 1978 Poultry Sci 57:1579-1585
subsequent changes in diet specification every 4 weeks as detailed in Table 1. In an attempt to produce compensatory growth, poults on this program received a 20.4% CP, 3087 kcal/kg diet from day-of-age to 12 weeks, followed by the control diets thereafter (Table 1). Diet selfselection was achieved by simultaneously providing diets containing concentrated sources of either protein or energy (diets 6 and 7, Table 1). All diets were in mash form. Three replicate groups of 15 male and three groups of 15 female Nicholas Large White poults hatched May 25th were assigned to each of the three treatments. At day-of-age these sexed poults were housed in 1.55 X 6.1 m floor pens of a windowed brooder house, with feed and water provided ad lib. In the case of the self-selection program, the two split diets were provided in separate troughs (0 to 4 weeks) or hanging tube feeders (4 weeks). Body weight and feed intake were recorded when poults were 4 and 8 weeks of age. At 8 weeks, poults within each treatment were re-randomized and transferred to 3.05 X 3.5 m pens of an open-sided pole barn, using four replicate groups of 10 turkeys/treatment for each sex. Feed intake and body weight were recorded at regular intervals. The following mean maximum and minimum pen temperatures, respectively, were recorded: 8 to 12 weeks, 23.4, 12.2; 12 to
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ABSTRACT Dietary self-selection studies with turkeys were undertaken since comparable work with broiler chickens indicated increased carcass fat content, an attribute of prime importance in turkey production. Separate sex Large White Nicholas turkey poults were reared using either 1) a conventional dietary regime, 2) a program that allowed potential for compensatory growth, or 3) free-choice of two "split diets" containing high levels of either protein (soybean meal) or energy (corn). Turkeys hatched May 25th were reared in litter floor pens of a brooder house to 8 weeks of age and then transferred to an open-sided pole barn and reared to a market age of 19 weeks for females and 21 weeks for males. Feed intake and body weight were recorded at regular intervals. Optimum performance was not achieved with compensatory growth due to prolonged feeding of a low-protein starter diet (20%, 0 to 12 weeks). Bodi sexes practicing diet self-selection were as heavy as control-fed birds at market age. Although consumption of the split diets resulted in increased intake of energy and protein, there was an indication for the toms of improved finish and fleshing carcass grades. Males offered the split diets were calculated to be consuming a dietary equivalent of 36% crude protein from 0 to 4 weeks. After this time self-selected protein requirements were very similar to those recently published by NRC (1977). Females required less protein than did males at all stages of the growth period.
LEESON AND SUMMERS
1580
TABLE 1 .—Diet composition anti feeding program Diet number 1
Ingredient
3
4
5
6
7
29.62 10.00 50.00 5.00 1.25 3.00 .25 .25 .50 .13
29.64 21.00 39.00 5.00 1.25 3.00 .25 .25 .50 .11
29.67 32.00 28.00 5.00 1.25 3.00 .25 .25 .50 .08
29.70 40.00 20.00 5.00 1.25 3.00 .25 .25 .50 .05
31.70 45.00 13.00 5.00 1.25 3.00 .25 .25 .50 .05
93.45 1.00 1.25 3.00 .25 .25 .50 .30
100.00
100.00
100.00
100.00
100.00
100.00
.20 100.00
28.4 2955 .56 1.71
24.4 3018 .48 1.42
20.4 3087 .40 1.12
17.6 3133 .33 .90
15.0 3188 .22 .71
45.8 2464 .95 2.99
8.2 3348 .28 .41
79.55 10.00 5.00 1.25 3.00 .25 .25 .50
Feeding program Control: Diet 1, 0-4 wk; Diet 2, 4 - 8 wk; Diet 3, 8-12 wk; Diet 4, 12-16 wk; Diet 5,16 wkSplit diets: Diets 6 and 7 throughout. Compensatory growth: Diet 3,0—12 wk; Diet 4,12—16 wk; Diet 5,16 wk-» a
See Leeson et al., 1976.
16 weeks, 19.0, 10.7; 16 to 21 weeks, 12.2, 2.8 C. Commensurate with commercial practice, females and males were marketed at 19 and 21 weeks of age, respectively. All birds were processed at a commercial plant, and carcasses graded by a government inspector according to Canada Department of Agriculture specifications. Two randomly-selected oven-ready carcasses per treatment replicate were halved with a band saw. After freezing, these two half carcasses per treatment replicate were blended together by pressing twice through a large animal mincer. A representative sample was freeze-dried and re-homogenized prior to analyses for dry matter, ether extractable fat and Kjeldahl crude protein. Data were analyzed by analyses of variance (Steel and Torrie, 1960) and, where applicable, means were tested by a multiple range test (Duncan, 1955). RESULTS Body weight of turkeys was influenced by diet treatment throughout the experiment, with
a comparable pattern being recorded fbr both sexes, (Table 2). Males were significantly (P<.01) heavier than females within each treatment group, while within each sex, turkeys on the compensatory growth (CG) program were significantly (FK.01) smaller than birds offered control or split diets. Up to 8 weeks of age, female poults offered the control diet were significantly (P<.01) heavier than birds fed the split diets; after this period no difference (P>.01) in body weight was observed. Male poults showed the same pattern to 8 weeks of age, while from 12 to 21 weeks, turkeys fed the split diets were numerically heavier than control fed birds with this difference being significant (P<.01) at 16 weeks of age. Diet had no consistent effect on feed efficiency (Table 3). From 8 to 12 weeks, CG females projected a superior (P<.01) feed efficiency compared to control fed turkeys, while from 16 to 21 weeks, males fed the split diets converted feed more efficiently (P<.01) than did birds offered the control diet. Re-randomization of birds at 8 weeks of age precluded statistical interpretation of overall feed efficiency.
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Ground corn Ground wheat Soybean meal (49%) Animal-vegetable fat Limestone Calcium phosphate Iodized salt (.015% KI) Mineral mix a Vitamin mix a DL-methionine L-lysine Total Calculated analyses Crude protein (%) ME (kcal/kg) Methionine (%) Lysine (%)
2
DIETARY SELF-SELECTION
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TABLE 2.—Body weight of Large White turkeys (g) Weeks of age Sex and diet
4
8
12
16
19?f 21 d
853 e 763 d 517 b
3144 e 2891 d 2194b
6111 d 6257 d 5024 c
8699 d 9226 e 743 5C
12,602b 13,02lb ll,290a
Female Control Split diets Compensatory growth
742 d 660= 453a
2574 d 2468 c 1608 a
4832bc 4616b 4035 a
6722 b 6651 b 5724 a
7,985 b 7,879 b 7,206 a
A
h f* ft ^
' ' ' ' Means in any one column followed by a different letter are significantly different (P<.01). Separate sex analysis.
Within each sex, a lower fleshing A grade for CG males compared to birds offered control or split diets was the only significant (P<.05) difference observed with the various carcass grading parameters (Table 4). Large variation in these subjective measurements resulted in instances of large but non-significant differences. Chemical analyses of these carcasses revealed significant (P<.05) dietary and sex differences with respect to fat and crude protein content (Table 5). Diet had no influence on the fat content of male carcasses, while the greatest fat
content was observed in females from control and split diet treatments. No sex difference was observed in the fat and protein content of the CG carcasses. The highest protein level was observed in male carcasses from the split diet and CG treatments, with that of the former being significantly higher than the level found in carcasses from the control treatment. Female CG carcasses contained significantly more protein than female carcasses from the control group. Calculated intakes of protein and energy are
TABLE 3.—Feed efficiency of Large White turkeys (g feed/g gain) Weeks of age 0-199e 0-21d
Sex and diet
0-4
4-8
8-12
12-16
16-199d 16-21d
Male Control Split diets Compensatory growth
1.53 1.76 1.74
1.75 1.81 1.67
2.61bc 2.34 a b 2.37 a b
3.70 3.98 3.37
4.85 b 4.14 a 4.47 a b
3.30 3.43 3.20
Female Control Split diets Compensatory growth
1.71 1.75 1.98
1.84 1.90 1.96
2.86 c 2.3 l a b 2.06 a
4.21 4.14 4.11
5.25 5.66 5.12
3.25 3.22 3.04
NS f
NS
•*
NS
•
' ' Means in any one column followed by a different letter are significantly different at the level of probability shown. Separate sex analysis. No statistical analysis undertaken due to re-randomization at 8 weeks. f NS, non-significant; *P<.05; ••P<.01.
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Male Control Split diets Compensatory growth
LEESON AND SUMMERS
For those birds fed the two split diets, it is possible from a consideration of total feed, energy, and protein intakes to calculate the dietary specifications of a single equivalent diet, the consumption of which results in an identical nutrient intake. These calculations are shown in Table 8. In a limited free-choice situation, both male and female turkeys showed a remarkably consistent reduction in protein, and increase in energy "requirement" 1 throughout the growth period. Males required substantially more protein than did females during the first 4 weeks of growth, while from 0 to 8 weeks there was a large reduction in protein requirement by these males. Up to 16 weeks of age, turkeys exhibited a constant increased energy requirement with age, while during the final finishing period males, and to a lesser
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shown in Tables 6 and 7, respectively. While the intake of each nutrient by the CG and control birds was governed by the dietary program (see footnote, Table 1), turkeys consuming the split diets had a choice of nutrients commensurate with the variation in specifications of the two diets offered (Table 1, diets 6 and 7). Compensatory growth turkeys consumed the least quantity of protein, with treatment differences being significant (P<.05) at most ages. The exception was a non-significant (P>.05) increase in protein intake by females during the 16 to 19 week period (Table 6). Up to 4 weeks of age, turkeys offered split diets consumed less protein than did the controls. After this time, response was different for each sex. With males there was an increased protein consumption by the split diet group from 4 to 16 weeks, with the difference being significant (P<.05) during the 8 to 16 week period. With females, however, there was no significant (P>.05) difference in protein consumption of control and split diet groups after 4 weeks of age (Table 6). As already shown with protein, CG turkeys generally consumed less energy than did turkeys from the other treatments (Table 7), with this difference being significant (P<.05) up to 16 weeks for males and up to 8 weeks for females. With the exception of an increased (P<.05) energy intake by the split diet fed males during the 12 to 16 week period, turkeys within each sex in control and split diet groups consumed similar quantities of energy throughout the test period (Table 7).
tiy different (P
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S
DIETARY SELF-SELECTION
1583
TABLE 5.—Eviscerated carcass composition
%DM
Fat (%DM)
Protein (% DM)
Control diet Male Female
33.7 35.6
26.0a 35.2C
58.6b 53.3a
Split diet Male Female
32.7 34.7
25.3 a 31.2bc
62.8C 56.2ab
Compensatory growth Male Female
33.0 33.9
25.1aa 28.5 b
59.8bc 59.0b
' ' Means in any column followed by a different letter are significantly different (P<.05).
extent females, showed a marked increase in energy requirement. DISCUSSION
throughout the entire growth period (unpublished observation). We have also recorded low protein intakes with starting Leghorn pullets (Leeson and Summers, 1978).
In contrast to results obtained with broiler chickens (Summers and Leeson, 1978), turkeys consuming the split diets were as heavy as control birds at market age. At 8 weeks of age, male and female broiler chickens were, respectively, 65 and 71% as heavy as control birds, compared to values of 92 and 96% recorded here for sexed 8-week-old turkeys. This improvement in growth rate of turkeys is undoubtedly related to increased protein consumption (see Table 8), since broilers consumed a dietary jequivalent of only 11% crude protein
In the previous section, diet protein values shown in Table 8 have been referred to as requirements. While turkeys selected these protein values on a free-choice basis, and are thus true requirements, they are obviously valid only within the confines imposed by the specifications of the split diets used. It is not suggested that they are finite requirement values. The pattern of both protein and energy selection (Table 8) shows the precision of this mechanism by the turkey, and gives support to current feeding practies.
TABLE 6.—Protein consumption of Large White turkeys (g) Weeks of age Sex and diet
0-4
4-8
8-12
12-16
16-199f 16-21 d
Male Control Split diet Compensatory growth
341d 312 c 176 a
978d 985d 613b
1578 d 1816 e 1359 c
1672 c 2278 d 1426b
2832 2748 2583
7401 8139 6157
Female Control Split diet Compensatory growth
325cd 260b 155a
821c 760 c 462 a
1236 b c 1175b 1020 a
1377 a b 1405 a b 1210 a
990 912 1020
4749 4512 3876
' ' ' ' Means in any one column followed by a different letter are significantly different (P<.05). Separate sex analysis. °No statistical analysis undertaken due to re-randomization at 8 weeks. f
0-1998 0 - 2 Id
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Sex and diet
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LEESON AND SUMMERS TABLE 7 .—Energy consumption of Large White turkeys (Meals) Weeks of age 0-199f 0-21d
0-4
4-8
8-12
12-16
Male Control Split diet Compensatory growth
3.55 c 3.55 c 2.66a
12.07 c 11.35 c 9.29b
23.91 d 23.54 d 20.59 c
29.74 c 36.63d 25.04 a b
60.21 64.28 54.93
129.48 139.35 112.51
Female Control Split diet Compensatory growth
3.38 b c 3.04 b 2.35a
10.01 b 9.49 b 7.00 a
18.70bc 17.14 a b 15.45a
24.48 a b 26.41 be 21.5ia
21.06 22.51 21.69
77.6 78.6 68.0
a
' , c ' Means in any one column followed by a different letter are significantly different (P<.01). Separate sex analysis. f No statistical analysis undertaken due to re-randomization at 8 weeks.
Although substantial sex differences were observed in protein requirements (Table 8), especially during the 0 to 4 week period, it is difficult to find supportive reported data, no doubt due to the complexity involved in deriving such results with conventional feeding programs over the entire growth period. In their latest report, the NRC (1977) suggest 28% dietary protein from 0 to 4 weeks, a value which is lower than that recorded for males and higher than that recorded here for females (Table 8). However, beyond 4 weeks of age, protein as well as energy values, are in close agreement with these NRC (1977) requirements. Why turkeys consumed more 'normal' levels of protein than did either broiler chickens or growing pullets when offered these split diets is
not readily apparent. Although amino acid content of the high protein diet (diet 6, Table 1) is the most likely cause, calculated levels showed there to be no overt imbalance. Failure to elicit a response with compensatory growth may be involved with prolonged feeding of the low protein starter diet. Thus, Auckland and Morris (1971) demonstrated compensatory growth after offering a 20% CP starter diet from 0 to 6 weeks compared to the 0 to 12 week period used here. Prolonged feeding of the starter diet was used in anticipation of comparable low protein intakes with turkeys offered split diets as previously found with broiler chickens and pullets. As detailed in the introduction, the expected advantage to accrue from the use of split diets was improved carcass fat content, especially in
TABLE 8.—Energy and protein level of "equivalent diet"3- consumed by turkeys offered split diets Weeks of age
Crude protein (%) Male Female Metabolizable energy (kcal/kg) Male Female
0-4
4-8
8-12
12-16
16-199 16-21d
36.2 25.2
25.6 23.9
23.1 20.9
19.3 16.8
14.0 13.1
2.90 2.95
2.94 2.99
Total energy or protein intake -j- total feed intake (Diet 6 and 7).
3.00 3.05
3.10 3.15
3.27 3.24
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Sex and diet
16-199e 16-21d
DIETARY SELF-SELECTION
ACKNOWLEDGMENT This work was financed by the National
Research Council of Canada, and the Ontario Ministry of Agriculture and Food. REFERENCES Auckland, J. N., and T. R. Morris, 1971. Compensatory growth after undernutrition in market turkeys: Effect of low protein feeding and realimentation in body composition. Brit. Poultry Sci. 12:137-150. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Leeson, S., and J. D. Summers, 1978. Step-up protein diets for growing pullets. Page 21—27 in Proc. Maryland Nutr. Conf. Washington, DC, March 16-18,1978. Leeson, S., J. D. Summers and A. E. Ferguson, 1976. Dietary salt and round heart disease in turkey poults with a note on the minimum level of supplementary salt necessary in corn-soybean diets. Poultry Sci. 55:2455-2460. Moran, E. T., 1977. Growth and meat yield in poultry. Page 145—173 in Growth and poultry meat production. K. N. Boorman and B. J. Wilson, ed. Brit. Poultry Sci. Ltd., Edinburgh. National Research Council, 1977. Nutrient requirements of poultry, 7th rev. ed. National Academy of Sciences, Washington, DC. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Ltd., New York, NY. Summers, J. D., and S. Leeson, 1978. Dietary selfselection of protein and energy by pullets and broiler chickens. Brit. Poultry Sci. 19:425-430.
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the males. Although carcass grading and chemical analysis failed to confirm this hypothesis, the numerical increases in breast and back finish grades for the male are of sufficient magnitude to warrant further studies. Comparable values of improved fleshing and carcass protein content for turkeys fed the split diets are likely to reflect the increased protein intake (Table 6). Although no statistical interpretation of overall feed efficiency and protein and energy intake was undertaken, these values are important in assessing the general implications of dietary self selection. With an overall feed efficiency of 3.43, males consuming split diets were less efficient than control birds. However, this reduced efficiency related to 'over consumption' of protein (Table 6) and to a lesser extent, energy (Table 7), must be considered in light of an improved carcass protein content. Females offered split diets appeared to utilize protein more efficiently than did control females, since with some 5% less protein consumed (Table 6) these birds were comparable to controls in both body weight and carcass protein content.
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INTRODUCTION A previous report from our laboratory (Summers and Leeson, 1978) described the production characteristics of broiler chickens allowed a degree of dietary self-selection. Although the simultaneous presentation of diets containing concentrated sources of either protein or energy resulted in inferior growth rate, carcass fat content was dramatically increased, especially for the male. While this latter effect is not usually regarded as advantageous with broiler chickens, it is of prime consideration in the production of both broiler and large-type turkeys (Moran, 1977). Since we are unaware of any data pertaining to diet self-selection by turkeys, an experiment was conducted to study such, with particular emphasis on the relationship between energy and protein consumption and carcass composition. Due to the slow initial growth rate of broilers offered these diets, (Summers and Leeson, 1978) it was also decided to compare diet self-selction with a compensatory growth rearing program. MATERIALS AND METHODS Experimental treatments consisted of conventional, self-selection, and compensatory growth rearing programs. Poults on the conventional program received a 28.4% crude protein (CP), 2955 kcal/kg diet at day-of-age, with 1978 Poultry Sci 57:1579-1585
subsequent changes in diet specification every 4 weeks as detailed in Table 1. In an attempt to produce compensatory growth, poults on this program received a 20.4% CP, 3087 kcal/kg diet from day-of-age to 12 weeks, followed by the control diets thereafter (Table 1). Diet selfselection was achieved by simultaneously providing diets containing concentrated sources of either protein or energy (diets 6 and 7, Table 1). All diets were in mash form. Three replicate groups of 15 male and three groups of 15 female Nicholas Large White poults hatched May 25th were assigned to each of the three treatments. At day-of-age these sexed poults were housed in 1.55 X 6.1 m floor pens of a windowed brooder house, with feed and water provided ad lib. In the case of the self-selection program, the two split diets were provided in separate troughs (0 to 4 weeks) or hanging tube feeders (4 weeks). Body weight and feed intake were recorded when poults were 4 and 8 weeks of age. At 8 weeks, poults within each treatment were re-randomized and transferred to 3.05 X 3.5 m pens of an open-sided pole barn, using four replicate groups of 10 turkeys/treatment for each sex. Feed intake and body weight were recorded at regular intervals. The following mean maximum and minimum pen temperatures, respectively, were recorded: 8 to 12 weeks, 23.4, 12.2; 12 to
1579
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ABSTRACT Dietary self-selection studies with turkeys were undertaken since comparable work with broiler chickens indicated increased carcass fat content, an attribute of prime importance in turkey production. Separate sex Large White Nicholas turkey poults were reared using either 1) a conventional dietary regime, 2) a program that allowed potential for compensatory growth, or 3) free-choice of two "split diets" containing high levels of either protein (soybean meal) or energy (corn). Turkeys hatched May 25th were reared in litter floor pens of a brooder house to 8 weeks of age and then transferred to an open-sided pole barn and reared to a market age of 19 weeks for females and 21 weeks for males. Feed intake and body weight were recorded at regular intervals. Optimum performance was not achieved with compensatory growth due to prolonged feeding of a low-protein starter diet (20%, 0 to 12 weeks). Bodi sexes practicing diet self-selection were as heavy as control-fed birds at market age. Although consumption of the split diets resulted in increased intake of energy and protein, there was an indication for the toms of improved finish and fleshing carcass grades. Males offered the split diets were calculated to be consuming a dietary equivalent of 36% crude protein from 0 to 4 weeks. After this time self-selected protein requirements were very similar to those recently published by NRC (1977). Females required less protein than did males at all stages of the growth period.
LEESON AND SUMMERS
1580
TABLE 1 .—Diet composition anti feeding program Diet number 1
Ingredient
3
4
5
6
7
29.62 10.00 50.00 5.00 1.25 3.00 .25 .25 .50 .13
29.64 21.00 39.00 5.00 1.25 3.00 .25 .25 .50 .11
29.67 32.00 28.00 5.00 1.25 3.00 .25 .25 .50 .08
29.70 40.00 20.00 5.00 1.25 3.00 .25 .25 .50 .05
31.70 45.00 13.00 5.00 1.25 3.00 .25 .25 .50 .05
93.45 1.00 1.25 3.00 .25 .25 .50 .30
100.00
100.00
100.00
100.00
100.00
100.00
.20 100.00
28.4 2955 .56 1.71
24.4 3018 .48 1.42
20.4 3087 .40 1.12
17.6 3133 .33 .90
15.0 3188 .22 .71
45.8 2464 .95 2.99
8.2 3348 .28 .41
79.55 10.00 5.00 1.25 3.00 .25 .25 .50
Feeding program Control: Diet 1, 0-4 wk; Diet 2, 4 - 8 wk; Diet 3, 8-12 wk; Diet 4, 12-16 wk; Diet 5,16 wkSplit diets: Diets 6 and 7 throughout. Compensatory growth: Diet 3,0—12 wk; Diet 4,12—16 wk; Diet 5,16 wk-» a
See Leeson et al., 1976.
16 weeks, 19.0, 10.7; 16 to 21 weeks, 12.2, 2.8 C. Commensurate with commercial practice, females and males were marketed at 19 and 21 weeks of age, respectively. All birds were processed at a commercial plant, and carcasses graded by a government inspector according to Canada Department of Agriculture specifications. Two randomly-selected oven-ready carcasses per treatment replicate were halved with a band saw. After freezing, these two half carcasses per treatment replicate were blended together by pressing twice through a large animal mincer. A representative sample was freeze-dried and re-homogenized prior to analyses for dry matter, ether extractable fat and Kjeldahl crude protein. Data were analyzed by analyses of variance (Steel and Torrie, 1960) and, where applicable, means were tested by a multiple range test (Duncan, 1955). RESULTS Body weight of turkeys was influenced by diet treatment throughout the experiment, with
a comparable pattern being recorded fbr both sexes, (Table 2). Males were significantly (P<.01) heavier than females within each treatment group, while within each sex, turkeys on the compensatory growth (CG) program were significantly (FK.01) smaller than birds offered control or split diets. Up to 8 weeks of age, female poults offered the control diet were significantly (P<.01) heavier than birds fed the split diets; after this period no difference (P>.01) in body weight was observed. Male poults showed the same pattern to 8 weeks of age, while from 12 to 21 weeks, turkeys fed the split diets were numerically heavier than control fed birds with this difference being significant (P<.01) at 16 weeks of age. Diet had no consistent effect on feed efficiency (Table 3). From 8 to 12 weeks, CG females projected a superior (P<.01) feed efficiency compared to control fed turkeys, while from 16 to 21 weeks, males fed the split diets converted feed more efficiently (P<.01) than did birds offered the control diet. Re-randomization of birds at 8 weeks of age precluded statistical interpretation of overall feed efficiency.
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Ground corn Ground wheat Soybean meal (49%) Animal-vegetable fat Limestone Calcium phosphate Iodized salt (.015% KI) Mineral mix a Vitamin mix a DL-methionine L-lysine Total Calculated analyses Crude protein (%) ME (kcal/kg) Methionine (%) Lysine (%)
2
DIETARY SELF-SELECTION
1581
TABLE 2.—Body weight of Large White turkeys (g) Weeks of age Sex and diet
4
8
12
16
19?f 21 d
853 e 763 d 517 b
3144 e 2891 d 2194b
6111 d 6257 d 5024 c
8699 d 9226 e 743 5C
12,602b 13,02lb ll,290a
Female Control Split diets Compensatory growth
742 d 660= 453a
2574 d 2468 c 1608 a
4832bc 4616b 4035 a
6722 b 6651 b 5724 a
7,985 b 7,879 b 7,206 a
A
h f* ft ^
' ' ' ' Means in any one column followed by a different letter are significantly different (P<.01). Separate sex analysis.
Within each sex, a lower fleshing A grade for CG males compared to birds offered control or split diets was the only significant (P<.05) difference observed with the various carcass grading parameters (Table 4). Large variation in these subjective measurements resulted in instances of large but non-significant differences. Chemical analyses of these carcasses revealed significant (P<.05) dietary and sex differences with respect to fat and crude protein content (Table 5). Diet had no influence on the fat content of male carcasses, while the greatest fat
content was observed in females from control and split diet treatments. No sex difference was observed in the fat and protein content of the CG carcasses. The highest protein level was observed in male carcasses from the split diet and CG treatments, with that of the former being significantly higher than the level found in carcasses from the control treatment. Female CG carcasses contained significantly more protein than female carcasses from the control group. Calculated intakes of protein and energy are
TABLE 3.—Feed efficiency of Large White turkeys (g feed/g gain) Weeks of age 0-199e 0-21d
Sex and diet
0-4
4-8
8-12
12-16
16-199d 16-21d
Male Control Split diets Compensatory growth
1.53 1.76 1.74
1.75 1.81 1.67
2.61bc 2.34 a b 2.37 a b
3.70 3.98 3.37
4.85 b 4.14 a 4.47 a b
3.30 3.43 3.20
Female Control Split diets Compensatory growth
1.71 1.75 1.98
1.84 1.90 1.96
2.86 c 2.3 l a b 2.06 a
4.21 4.14 4.11
5.25 5.66 5.12
3.25 3.22 3.04
NS f
NS
•*
NS
•
' ' Means in any one column followed by a different letter are significantly different at the level of probability shown. Separate sex analysis. No statistical analysis undertaken due to re-randomization at 8 weeks. f NS, non-significant; *P<.05; ••P<.01.
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Male Control Split diets Compensatory growth
LEESON AND SUMMERS
For those birds fed the two split diets, it is possible from a consideration of total feed, energy, and protein intakes to calculate the dietary specifications of a single equivalent diet, the consumption of which results in an identical nutrient intake. These calculations are shown in Table 8. In a limited free-choice situation, both male and female turkeys showed a remarkably consistent reduction in protein, and increase in energy "requirement" 1 throughout the growth period. Males required substantially more protein than did females during the first 4 weeks of growth, while from 0 to 8 weeks there was a large reduction in protein requirement by these males. Up to 16 weeks of age, turkeys exhibited a constant increased energy requirement with age, while during the final finishing period males, and to a lesser
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shown in Tables 6 and 7, respectively. While the intake of each nutrient by the CG and control birds was governed by the dietary program (see footnote, Table 1), turkeys consuming the split diets had a choice of nutrients commensurate with the variation in specifications of the two diets offered (Table 1, diets 6 and 7). Compensatory growth turkeys consumed the least quantity of protein, with treatment differences being significant (P<.05) at most ages. The exception was a non-significant (P>.05) increase in protein intake by females during the 16 to 19 week period (Table 6). Up to 4 weeks of age, turkeys offered split diets consumed less protein than did the controls. After this time, response was different for each sex. With males there was an increased protein consumption by the split diet group from 4 to 16 weeks, with the difference being significant (P<.05) during the 8 to 16 week period. With females, however, there was no significant (P>.05) difference in protein consumption of control and split diet groups after 4 weeks of age (Table 6). As already shown with protein, CG turkeys generally consumed less energy than did turkeys from the other treatments (Table 7), with this difference being significant (P<.05) up to 16 weeks for males and up to 8 weeks for females. With the exception of an increased (P<.05) energy intake by the split diet fed males during the 12 to 16 week period, turkeys within each sex in control and split diet groups consumed similar quantities of energy throughout the test period (Table 7).
tiy different (P
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DIETARY SELF-SELECTION
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TABLE 5.—Eviscerated carcass composition
%DM
Fat (%DM)
Protein (% DM)
Control diet Male Female
33.7 35.6
26.0a 35.2C
58.6b 53.3a
Split diet Male Female
32.7 34.7
25.3 a 31.2bc
62.8C 56.2ab
Compensatory growth Male Female
33.0 33.9
25.1aa 28.5 b
59.8bc 59.0b
' ' Means in any column followed by a different letter are significantly different (P<.05).
extent females, showed a marked increase in energy requirement. DISCUSSION
throughout the entire growth period (unpublished observation). We have also recorded low protein intakes with starting Leghorn pullets (Leeson and Summers, 1978).
In contrast to results obtained with broiler chickens (Summers and Leeson, 1978), turkeys consuming the split diets were as heavy as control birds at market age. At 8 weeks of age, male and female broiler chickens were, respectively, 65 and 71% as heavy as control birds, compared to values of 92 and 96% recorded here for sexed 8-week-old turkeys. This improvement in growth rate of turkeys is undoubtedly related to increased protein consumption (see Table 8), since broilers consumed a dietary jequivalent of only 11% crude protein
In the previous section, diet protein values shown in Table 8 have been referred to as requirements. While turkeys selected these protein values on a free-choice basis, and are thus true requirements, they are obviously valid only within the confines imposed by the specifications of the split diets used. It is not suggested that they are finite requirement values. The pattern of both protein and energy selection (Table 8) shows the precision of this mechanism by the turkey, and gives support to current feeding practies.
TABLE 6.—Protein consumption of Large White turkeys (g) Weeks of age Sex and diet
0-4
4-8
8-12
12-16
16-199f 16-21 d
Male Control Split diet Compensatory growth
341d 312 c 176 a
978d 985d 613b
1578 d 1816 e 1359 c
1672 c 2278 d 1426b
2832 2748 2583
7401 8139 6157
Female Control Split diet Compensatory growth
325cd 260b 155a
821c 760 c 462 a
1236 b c 1175b 1020 a
1377 a b 1405 a b 1210 a
990 912 1020
4749 4512 3876
' ' ' ' Means in any one column followed by a different letter are significantly different (P<.05). Separate sex analysis. °No statistical analysis undertaken due to re-randomization at 8 weeks. f
0-1998 0 - 2 Id
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Sex and diet
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LEESON AND SUMMERS TABLE 7 .—Energy consumption of Large White turkeys (Meals) Weeks of age 0-199f 0-21d
0-4
4-8
8-12
12-16
Male Control Split diet Compensatory growth
3.55 c 3.55 c 2.66a
12.07 c 11.35 c 9.29b
23.91 d 23.54 d 20.59 c
29.74 c 36.63d 25.04 a b
60.21 64.28 54.93
129.48 139.35 112.51
Female Control Split diet Compensatory growth
3.38 b c 3.04 b 2.35a
10.01 b 9.49 b 7.00 a
18.70bc 17.14 a b 15.45a
24.48 a b 26.41 be 21.5ia
21.06 22.51 21.69
77.6 78.6 68.0
a
' , c ' Means in any one column followed by a different letter are significantly different (P<.01). Separate sex analysis. f No statistical analysis undertaken due to re-randomization at 8 weeks.
Although substantial sex differences were observed in protein requirements (Table 8), especially during the 0 to 4 week period, it is difficult to find supportive reported data, no doubt due to the complexity involved in deriving such results with conventional feeding programs over the entire growth period. In their latest report, the NRC (1977) suggest 28% dietary protein from 0 to 4 weeks, a value which is lower than that recorded for males and higher than that recorded here for females (Table 8). However, beyond 4 weeks of age, protein as well as energy values, are in close agreement with these NRC (1977) requirements. Why turkeys consumed more 'normal' levels of protein than did either broiler chickens or growing pullets when offered these split diets is
not readily apparent. Although amino acid content of the high protein diet (diet 6, Table 1) is the most likely cause, calculated levels showed there to be no overt imbalance. Failure to elicit a response with compensatory growth may be involved with prolonged feeding of the low protein starter diet. Thus, Auckland and Morris (1971) demonstrated compensatory growth after offering a 20% CP starter diet from 0 to 6 weeks compared to the 0 to 12 week period used here. Prolonged feeding of the starter diet was used in anticipation of comparable low protein intakes with turkeys offered split diets as previously found with broiler chickens and pullets. As detailed in the introduction, the expected advantage to accrue from the use of split diets was improved carcass fat content, especially in
TABLE 8.—Energy and protein level of "equivalent diet"3- consumed by turkeys offered split diets Weeks of age
Crude protein (%) Male Female Metabolizable energy (kcal/kg) Male Female
0-4
4-8
8-12
12-16
16-199 16-21d
36.2 25.2
25.6 23.9
23.1 20.9
19.3 16.8
14.0 13.1
2.90 2.95
2.94 2.99
Total energy or protein intake -j- total feed intake (Diet 6 and 7).
3.00 3.05
3.10 3.15
3.27 3.24
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Sex and diet
16-199e 16-21d
DIETARY SELF-SELECTION
ACKNOWLEDGMENT This work was financed by the National
Research Council of Canada, and the Ontario Ministry of Agriculture and Food. REFERENCES Auckland, J. N., and T. R. Morris, 1971. Compensatory growth after undernutrition in market turkeys: Effect of low protein feeding and realimentation in body composition. Brit. Poultry Sci. 12:137-150. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Leeson, S., and J. D. Summers, 1978. Step-up protein diets for growing pullets. Page 21—27 in Proc. Maryland Nutr. Conf. Washington, DC, March 16-18,1978. Leeson, S., J. D. Summers and A. E. Ferguson, 1976. Dietary salt and round heart disease in turkey poults with a note on the minimum level of supplementary salt necessary in corn-soybean diets. Poultry Sci. 55:2455-2460. Moran, E. T., 1977. Growth and meat yield in poultry. Page 145—173 in Growth and poultry meat production. K. N. Boorman and B. J. Wilson, ed. Brit. Poultry Sci. Ltd., Edinburgh. National Research Council, 1977. Nutrient requirements of poultry, 7th rev. ed. National Academy of Sciences, Washington, DC. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Ltd., New York, NY. Summers, J. D., and S. Leeson, 1978. Dietary selfselection of protein and energy by pullets and broiler chickens. Brit. Poultry Sci. 19:425-430.
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the males. Although carcass grading and chemical analysis failed to confirm this hypothesis, the numerical increases in breast and back finish grades for the male are of sufficient magnitude to warrant further studies. Comparable values of improved fleshing and carcass protein content for turkeys fed the split diets are likely to reflect the increased protein intake (Table 6). Although no statistical interpretation of overall feed efficiency and protein and energy intake was undertaken, these values are important in assessing the general implications of dietary self selection. With an overall feed efficiency of 3.43, males consuming split diets were less efficient than control birds. However, this reduced efficiency related to 'over consumption' of protein (Table 6) and to a lesser extent, energy (Table 7), must be considered in light of an improved carcass protein content. Females offered split diets appeared to utilize protein more efficiently than did control females, since with some 5% less protein consumed (Table 6) these birds were comparable to controls in both body weight and carcass protein content.
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