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Independent Effects of Dietary Metabolizable Energy and Protein Concentrations on Performance and Carcass Characteristics of Tom Turkeys1
Independent Effects of Dietary Metabolizable Energy and Protein Concentrations on Performance and Carcass Characteristics of Tom Turkeys1 JERRY L. SELL, ROBERT J. HASIAK, and WILLIAM J. OWINGS Department of Animal Science, Iowa State University, Ames, Iowa 50011 (Received for publication October 9, 1984) ABSTRACT An experiment was conducted to determine the independent and interaction effects of dietary metabolizable energy (ME) and protein concentrations on performance of Large White toms from 9 to 20 weeks of age. Diet treatments consisted of a complete factorial arrangement of three ME concentrations and three protein concentrations within each age interval (9 to 12, 12 to 16, and 16 to 20 weeks). The different ME concentrations were obtained by using an animalvegetable fat blend at 0, 4, or 8% of the diets. Dietary protein levels tested provided approximately 88, 97, or 107% of those recommended by National Research Council (1977) for each age interval. The ME concentrations represented 95, 100, or 105% of those used most frequently in commercial feeding programs in the central United States. Dietary ME and protein concentrations had significant (P<.03) independent effects on turkey performance. As each diet variable was increased, gain in body weight and feed efficiency were improved. Increasing dietary ME reduced the amount of protein consumed per kilogram of gain but not the ME consumed per kilogram of gain. Protein consumed per kilogram gain increased as dietary protein increased, while ME intake per kilogram gain decreased. Carcass composition and parts yield of the carcass were affected only slightly by dietary ME and protein concentration. No significant (P>.10) interaction effects of dietary ME and protein were detected, except in the instance of absolute quantity of carcass protein (P<.07). Data from this experiment and results of other research suggest that the use of "optimum ME-to-protein ratios" as a restriction in formulation of turkey diets may be inappropriate and that greater emphasis should be placed on the nutritional and economic implications of the independent effects of ME and protein on rate of growth and feed efficiency. (Key words: turkeys, metabolizable energy, protein, carcass) 1985 Poultry Science 64:1527-1535
INTRODUCTION Supplemental fats are used frequently to increase the metabolizable energy (ME) concentration of diets for growing turkeys, and the generally favorable effects of increasing dietary ME on performance of turkeys is well documented (Sunde, 1954; Waibel, 1958; Touchburn and Naber, 1966; Jensen et al, 1970; Potter et al, 1974; Sell and Owings, 1981, 1984; Owen et al, 1981). Much of the foregoing research was done with diets in which the concentration of protein remained constant, irrespective of change in ME concentration of the diet. In other instances, the concentration of protein and amino acids was changed com-
1 Journal Paper No. J-11639 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project 2561.
mensurate with changes in dietary ME. The importance of maintaining desirable energy-toprotein ratios, as suggested by Combs and Romoser (1955), has been a commonlyaccepted principle of poultry nutrition. Several reports, however (Day and Hill, 1957; Balloun et al, 1959; Touchburn and Naber, 1966), indicated that widely varying ME-to-protein ratios could be used without adversely affecting performance of growing turkeys. Data presented by Jensen et al. (1970) and Waibel (1978) showed that when various combinations of protein and ME concentrations were fed, significant main effects of protein and ME were observed, but that no protein X ME level interaction occurred. Sell and Owings (1981) and Owings and Sell (1982) found that increasing the ME, by using supplemental fat, improved performance of toms and hens, respectively, whether the concentrations of key nutrients remained constant or were increased commensurate with changes in ME level.
1527
SELL ET AL.
1528
The research reported here was conducted to obtain additional information about the independent and possible interaction effects of dietary ME and protein on weight gain and efficiency of nutrient utilization of growing turkeys. MATERIALS AND METHODS Nicholas Large White, male poults were brooded and grown in total confinement. Thirty one-day-old poults were placed in each of 36 floor pens. Each of nine diet treatments was assigned to four pens. Floor space allowance was .248 m 2 per turkey in the 18 pens of Barn E and .278 m 2 per turkey in Barn F. All treatments were represented equally in the two barns. The nine diet treatments consisted of a complete factorial arrangement of three ME levels and three protein levels within the age intervals of 9 to 12, 12 to 16, and 16 to 20 weeks of age. Treatments were not begun until 9 weeks of age because Sell and Owings (1984) reported that responses of turkeys to increased dietary ME were greatest after this age. The different ME levels were obtained by using an animal-vegetable fat blend (see footnote, Table 1) at 0, 4, or 8% of the diets. The ME and protein levels of the diets were adjusted for the respective age intervals as shown in Table 1. Dietary ME and protein were supplied primarily by corn and soybean meal, with some contributions from meat and bone meal, hydrolyzed feather meal, and DL-methionine. Least-cost, linear programming was used to formulate all diets. Protein content of corn and soybean meal, as determined by laboratory analysis, was used in the formulation. Corn and soybean meal protein levels were 8.1 and 47.1%, respectively, for the diets fed from 9 to 12 weeks of age and 8.4 and 48.2% protein, respectively, for diets fed from 12 to 20 weeks of age. Amino acid analyses listed by the National Research Council (1977), adjusted to the appropriate protein concentration of the ingredients, were used to calculate the amino acid concentration of the diets. Diet formulation was done so that the same relative concentrations of total sulfur amino acids (TSAA) and lysine in the protein were maintained within each age interval, irrespective of protein level of the diet. Ingredient composition of the diets, fed from 9 to 12 weeks of age, are presented in Table 2 to illustrate the alterations in ingredient use that occurred with changes in protein and added fat concentrations.
The dietary protein levels tested provided approximately 88, 97, and 107% of the level recommended by National Research Council (1977) for each age interval. The ME concentrations selected represented about 95, 100, and 105% of those commonly used in commercial feeding programs of the central United States. All diets were provided in mash form ad libitum. Body weights were determined at 9, 12, 16, and 20 weeks of age. Feed-consumption data were recorded at 12, 16, and 20 weeks. Records of mortality and causes of mortality were maintained. Approximately 10% of the toms from each pen were processed through the Iowa State University Meats Laboratory, where yield and grade data were obtained. Data were analyzed statistically by the Statistical Analysis System (Barr et al, 1979). RESULTS AND DISCUSSION Dietary ME and protein concentrations each had significant independent effects on gain in body weight and feed efficiency of toms from 9 to 20 weeks of age (Table 3). As each diet variable increased, performance was improved. Increasing dietary ME also reduced the amount of protein consumed per unit of weight gain but had no significant effect on amount of ME consumed per unit of gain. As dietary protein level increased, the amount of protein consumed per gain increased, while the ME consumed per gain decreased. Statistical analysis of data for each production characteristic showed that no significant (P>.10) interaction effect of dietary ME and protein occurred. Dietary protein concentration did not significantly affect carcass yields of the 20week-old toms. Increasing diet ME by adding fat, however, had the significant effect of a slight, inconsistent increase in yields (Table 4). The interaction effect of dietary protein and ME on yield was not significant (P>.10). Similarly, there were no significant main effects of dietary protein or the protein by ME interaction on percent water, protein, or ME in eviscerated carcasses. However, as dietary ME increased, carcass water decreased and carcass fat increased, reflecting a significant (P<.02) main effect of ME. The quantities of fat in the carcass were affected most extensively (Table 4). As dietary ME or protein concentration increased, quantity of carcass fat increased, especially in the instance of ME. Concurrently, amounts of carcass water decreased. There was no significant
22.0
-
.75
.83 .83 .83
.75 .75 .75
.68 .68 .68
(%) •
TSAA
1.35
1.19 1.19 1.19
1.08 1.08 1.08
.97 .97 .97
Lysine
3100
3070 3230 3390
3070 3230 3 390
3072 3232 3392
(kcal/kg)
ME
19.0
20.4 20.4 20.4
18.5 18.5 18.5
16.65 16.65 16.65
Protein i
.65
.72 .72 .72
.65 .65 .65
.59 .59 .59
('/a)
TSAA
12 to 16
Age of t:urkeys, wk
1.00
1.01 1.01 1.01
.92 .92 .92
.83 .83 .83
Lysin
3
2
Laboratory analysis showed that crude protein concentrations of the diets were within .4% of the calculated values
ME = Metabolizable energy, TSAA = total sulfur amino acids, NRC = National Research Council.
An animal-vegetable fat blend, which was analyzed to contain an MIU of 3.8% and the following fatty acid as C 1 6 : , , 2 . 5 ; C I 8 , 8 . 8 ; C J 8 : I , 3 0 . 4 ; C 1 8 : 2 , 30.8;C 1 8 : 3 , 3.3;other, 3.3.
NRC (1977)
3000
0 4 8
High High High
23.1 23.1 23.1
0 4 8
Medium Medium Medium
18.9 18.9 18.9
2970 3130 3290
2975 3135 3295
0 4 8
Low Low Low
21.0 21.0 21.0
(kcal/kg)
(%)
9 to 12
Protein 3
2970 3130 3295
ME2
Protein
Supplemental fat 1
TABLE 1. Selected characteristics of the dietary treatments
2975 19.2 .97 .68 .42 1.20 .74
.10
66.98 21.12 5.34 4.00 .12 .93 .81 .30 .30
Low 0
3135 19.1 .97 .68 .40 1.20 .75
61.49 23.64 2.15 4.00 1.14 1.26 1.66 .30 .30 4.00 .06
Low 4
3295 19.2 .99 .70 .43 1.20 .75
55.27 26.08 2.00 4.50 .45 1.24 1.73 .30 .30 8.00 .13
Low 8
2970 21.4 1.08 .75 .44 1.20 .75
.09
64.32 24.22 6.00 2.16 1.10 .92 .59 .30 .30
Medium 0
3130 20.9 1.08 .75 .43 1.20 .74
58.81 24.14 6.00 3.50 1.39 .87 .60 .30 .30 4.00 .09
(ni \
Medium 4
3
M 8
2
The mineral premix contributed the following per kilogram of diet: manganese, 70 mg; zinc, 40 mg; iron, 37 mg; co
' T h e vitamin premix contributed the following per kilogram of diet; vitamin A, 5000 IU; vitamin D 3 , 1500 IU; v mg; riboflavin, 2.7 mg; pantothenic acid, 7 mg; niacin, 75 mg; choline, 509 mg; folacin, .55 mg; biotin, 75 /xg.
Calculated analysis Metabolizable energy, kcal/kg Protein, by analysis, % Lysine, % Total sulfur amino acids, % Methionine, % Calcium, % Total phosphorus, %
Corn (8.1% protein) Soybean meal (47.1% protein) Meat and bone meal (50% protein) Dehydrated alfalfa meal (17% protein) Hydrolyzed feather meal Ground limestone Dicalcium phosphate Vitamin premix 1 Mineral premix 2 Animal-vegetable fat DL-Methionine
Protein level added fat, %
TABLE 2. Ingredient composition of diets fed from 9 to 12 weeks of
DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS
1531
TABLE 3. Influence of supplemental fat and dietary protein on performance of torn turkeys From 9 to 20 wk of age Dietary ME
Body weight
Low1 Low Low
Low Medium High
Medium Medium Medium
HI
Dietary protein
Weight gain
Feed/ gain
Protein/ gain
ME/gain
12.31 12.35 12.65
8.57 8.60 8.90
3.73 3.49 3.33
(kg/kg)
(Mcal/kg)
.61 .57 .54
11.51 11.33 11.35
Low Medium High
12.17 12.94 12.55
8.38 9.05 8.74
3.71 3.43 3.30
.67 .62 .59
11.43 11.10 11.22
Low Medium High
12.64 12.79 13.09
8.83 9.02 9.28
3.53 3.30 3.18
.70 .65 .63
10.89 10.71 10.82
.34
.11
.02
.36
(*%>
Standard deviation of means Source of variation ME Protein ME X protein 1
Probabilities of significance .03 .04 .30
.001 .002 .98
.001 .001 .98
.30 .001 .99
Protein and metabolizable energy (ME) concentrations of diets for each age interval are shown in Table 1.
interaction effect between dietary ME and protein on quantities of water or fat in the carcass. Quantities of protein in carcasses increased as dietary ME increased. This main effect of ME was significant (P<.05). However, there was an indication of dietary ME by protein interaction effect (P<.07), seemingly as a result of the greater influence of ME on carcass protein, when fed in conjunction with higher levels of protein. The changes in carcass composition of turkeys in this research, related to increasing dietary ME, correspond with those observed by Salmon and O'Neil (1971) and Webb et al. (1975). More recently, Hasiak (1985) described the increases in fat content of different parts of carcasses of turkeys, fed levels of added dietary fat ranging from 2 to 8%. In all instances, there was a linear relationship between dietary fat and ME, and fat in parts of the carcass. The main effect of dietary protein, the absolute increase in quantity of carcass fat, also agrees with earlier reports. Summers (1983) presented data showing that carcass fat of turkeys increased as dietary protein level
increased. Salmon (1984) indicated that an increase in dietary protein fed to broiler turkeys tended to increase "fat score" of the carcasses, although there was little effect on abdominal fat pad. The favorable effect of ME on quantities of carcass protein suggests that this source of additional energy augmented true growth. Also, the ME by protein interaction effect on quantities of carcass protein indicates that the extent of the effect of ME was contingent, in part, on dietary protein level. The proportion of parts in the eviscerated carcasses and the percentage of meat, skin, and bone contained in breasts and thighs are shown in Table 5. In most instances, dietary ME and protein did not significantly (P>.10) affect these carcass traits. However, ME level of the diet altered the percentage of meat and skin (P«.003 and P<.07, respectively) in the breast. These effects of ME were inconsistent; meat of the breast was increased by the intermediate level of ME but was not changed by the high level of ME, whereas skin of the breast decreased slightly with the intermediate ME level
1532
SELL ET AL. TABLE 4. Influence of supplemental fat and dietary protein on yield and composition of eviscerated carcasses of Large White male turkeys
Dietary protein
Dietary ME
Carcass yield
Water
(% of live weight) Low Low Low
1
Protein
Fat
Water
Protein
Fat
(kg carcass)
(% of carcass)
Low Medium High
81.65 83.15 79.88
65.53 65.35 64.70
19.52 19.68 19.02
10.95 11.60 12.45
8.06 8.07 8.18
2.40 2.43 2.41
1.35 1.43 1.58
Medium Medium Medium
Low Medium High
81.72 82.30 82.65
65.45 64.38 64.32
19.00 19.02 19.24
12.00 12.38 12.95
7.97 8.33 8.07
2.31 2.46 2.41
1.46 1.60 1.62
High High High
Low Medium High
80.91 83.24 80.91
65.50 65.25 64.08
19.18 19.51 19.10
11.48 11.80 13.20
8.28 8.34 8.39
2.42 2.50 2.50
1.45 1.51 1.73
1.39
.91
.56
1.08
.28
.11
.14
.05 .33 .07
.01 .02 .92
Standard deviation of means Source of variation ME Protein ME X protein 1
Probabilities of significance .02 .40 .13
.02 .46 .72
.47 .38 .55
.02 .23 .93
.09 .08 .14
Protein and metabolizable energy (ME) concentrations of diets for each age interval are shown in Table 1.
and increased notably with the high ME level. A protein effect (P<.06) was noted only with the proportion of bone in the thigh; proportion of bone was increased when the high protein diets were fed. There was no significant (P».10) interaction effects of dietary ME and protein on proportions of parts in carcasses. Total mortality during the 9 to 20-week age interval was 5.9%. More than 50% of the deaths were the result of aortic and(or) renal hemorrhage. Mortality was uniformly distributed among diet treatment groups. The results of this experiment support previous observations made with turkeys that dietary ME and protein exert independent effects on growth and feed efficiency. Also, the data show that there were no significant interaction effects between dietary ME and protein, with respect to turkey performance, even though a relatively wide range of ME and protein levels were tested. Balloun et al. (1959), working with poults from hatch to 6 weeks of age, found that the interaction effects between dietary ME and protein were negligible as compared with the main effects of each. Jensen et al. (1970) and Waibel (1978) reported similar findings after
feeding diets of various ME and protein contents to growing-finishing turkeys. Sell and Owings (1981) also were unable to detect ME X protein interaction effects on growth and feed efficiency of turkeys from hatch to 20 weeks of age. The absence of significant ME X protein interaction effects on growth and feed efficiency, in experiments designed to detect these effects, raises a question about the relevance of the commonly-accepted concept of "optimum energy to protein ratio." Balloun et al. (1959) stated that the ratio of dietary energy and protein was of relatively minor importance in determining the performance of young turkeys. Recently, Pesti and Fletcher (1983) evaluated a large amount of data obtained with broiler chickens and also found that differences in energy-to-protein ratios of diets was of secondary importance to dietary energy or protein concentrations per se for explaining variation in growth rate or carcass composition. In the current research, a relatively wide range of ME-to-protein ratios was tested within each age interval (Table 6). Regression analysis of the data showed that neither weight gains nor feed
DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS
1533
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DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS efficiencies by poults, within any of the three age intervals, were related significantly with ME-to-protein ratios of the diets (Table 6). Correlation coefficients between ME-to-protein ratios and weight gain ranged from .06 to .28 across age intervals, while those for feed efficiency varied from .03 to .10. Data on carcass composition obtained from the current research indicated that a ME protein interaction may affect absolute amounts of protein in turkey carcasses, and this deserves further investigation. Also, in view of potential importance to further processing of turkey parts, the effects of dietary ME on proportions of meat and skin in the breast should be given consideration in future research. From a practical point of view, data from this experiment and results of other research suggest that the use of "optimum ME-to-protein ratios" as a guideline for ration formulation for growing turkeys may be inappropriate. Use of optimum ME-to-protein ratios may place an unnecessary, costly constraint on formulation. It seems more appropriate to place greater emphasis on the nutritional and economic implications of the independent effects of dietary ME and dietary protein on growth, feed efficiency, and carcass composition of turkeys and to minimize the concern about optimum ME-to-protein ratios.
REFERENCES Balloun, S. L., W. J. Owings, J. L. Sell, and R. E. Phillips, 1959. Energy and protein requirements for turkey starting diets. Poultry Sci. 38:1328— 1340. Barr, A. J., J. H. Goodnight, J. P. Sail, W. H. Blair, and D. M. Chilko, 1979. SAS User's Guide. J. T. Helwig and K. A. Council, ed. SAS Inst., Inc., Raleigh, NC. Combs, G. F., and G. L. Romoser, 1955. A new approach to poultry feed formulation. Maryland Agric. Exp. Stn. Misc. Publ. 226. Day, E. J„ and J. E. Hill, 1957. The effect of calorie: protein ratio of the ration on growth and feed efficiency of turkeys. Poultry Sci. 36:773-779. Hasiak, R. J., 1985. Effect of supplemental dietary fat and growing season on the yield and composition
1535
of torn turkeys. Poultry Sci. 64: (in press). Jensen, L. S., G. W. Schumaier, and J. D. Latshaw, 1970. Extra-caloric effect of dietary fat for developing turkeys as influenced by calorie: protein ratio. Poultry Sci. 49:1697-1704. National Research Council, 1977. Nutrient Requirements of Poultry. 7th ed. Natl. Acad. Sci., Washington, DC. Owen, J. A., P. W. Waldroup, C. J. Mabray, and P. J. Slagter, 1981. Response of growing turkeys to dietary energy levels. Poultry Sci. 60:418—424. Owings, W. J., and J. L. Sell, 1982. Performance of growing turkey hens as influenced by supplemental dietary fat and different ME:nutrient ratios. Poultry Sci. 61:1897-1904. Pesti, G. M., and D. L. Fletcher, 1983. The response of male broiler chickens to diets with various protein and energy contents during the growing phase. Br. Poult. Sci. 24:91-99. Potter, L. M., J. R. Shelton, and L. G. Melton, 1974. Zinc bacitracin and added fat in diets of growing turkeys. Poultry Sci. 53:2072-2081. Salmon, R. E., 1984. Effect of grower and finisher protein on performance, carcass grade, and meat yield of turkey broilers. Poultry Sci. 63:1980— 1986. Salmon, R. E., and J. B. O'Neil, 1971. The effect of the level and source of dietary fat on the growth, feed efficiency, grade, and carcass composition of turkeys. Poultry Sci. 50:1456-1467. Sell, J. L., and W. J. Owings, 1981. Supplemental fat and metabolizable-to-nutrient ratios for growing turkeys. Poultry Sci. 60:2293-2305. Sell, J. L„ and W. J. Owings, 1984. Influence of feeding supplemental fat by age sequence on the performance of growing turkeys. Poultry Sci. 6 3 : 1184-1189. Summers, J. E., 1983. Carcass composition of the heavy turkey. Turkeys 31(2): 3 0 - 3 1 . Sunde, M. L., 1954. The use of animal fats in poultry feeds. J. Am. Oil Chem. Soc. 31:49-52. Touchburn, S. P., and E. C. Naber, 1966. The energy value of fats for growing turkeys. Pages 190— 195 in Proc. 13th World's Poult. Congr., Kiev, USSR. Waibel, P. E., 1958. Effectiveness of unknown growth factors, antibiotic, and animal fat in turkey poult rations. Poultry Sci. 37:1144-1149. Waibel, P. E., 1978. Studies on protein and energy requirements of turkeys during the growing period. Pages 143—154 in Proc. 39th Minnesota Nutr. Conf., Univ. Minnesota, St. Paul, MN. Webb, J. E., J. D. Yates, and C. C. Brunson, 1975. Effect of dietary variables on turkey fat quantity, quality, and stability. Poultry Sci. 54:1349. (Abstr.)
INTRODUCTION Supplemental fats are used frequently to increase the metabolizable energy (ME) concentration of diets for growing turkeys, and the generally favorable effects of increasing dietary ME on performance of turkeys is well documented (Sunde, 1954; Waibel, 1958; Touchburn and Naber, 1966; Jensen et al, 1970; Potter et al, 1974; Sell and Owings, 1981, 1984; Owen et al, 1981). Much of the foregoing research was done with diets in which the concentration of protein remained constant, irrespective of change in ME concentration of the diet. In other instances, the concentration of protein and amino acids was changed com-
1 Journal Paper No. J-11639 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project 2561.
mensurate with changes in dietary ME. The importance of maintaining desirable energy-toprotein ratios, as suggested by Combs and Romoser (1955), has been a commonlyaccepted principle of poultry nutrition. Several reports, however (Day and Hill, 1957; Balloun et al, 1959; Touchburn and Naber, 1966), indicated that widely varying ME-to-protein ratios could be used without adversely affecting performance of growing turkeys. Data presented by Jensen et al. (1970) and Waibel (1978) showed that when various combinations of protein and ME concentrations were fed, significant main effects of protein and ME were observed, but that no protein X ME level interaction occurred. Sell and Owings (1981) and Owings and Sell (1982) found that increasing the ME, by using supplemental fat, improved performance of toms and hens, respectively, whether the concentrations of key nutrients remained constant or were increased commensurate with changes in ME level.
1527
SELL ET AL.
1528
The research reported here was conducted to obtain additional information about the independent and possible interaction effects of dietary ME and protein on weight gain and efficiency of nutrient utilization of growing turkeys. MATERIALS AND METHODS Nicholas Large White, male poults were brooded and grown in total confinement. Thirty one-day-old poults were placed in each of 36 floor pens. Each of nine diet treatments was assigned to four pens. Floor space allowance was .248 m 2 per turkey in the 18 pens of Barn E and .278 m 2 per turkey in Barn F. All treatments were represented equally in the two barns. The nine diet treatments consisted of a complete factorial arrangement of three ME levels and three protein levels within the age intervals of 9 to 12, 12 to 16, and 16 to 20 weeks of age. Treatments were not begun until 9 weeks of age because Sell and Owings (1984) reported that responses of turkeys to increased dietary ME were greatest after this age. The different ME levels were obtained by using an animal-vegetable fat blend (see footnote, Table 1) at 0, 4, or 8% of the diets. The ME and protein levels of the diets were adjusted for the respective age intervals as shown in Table 1. Dietary ME and protein were supplied primarily by corn and soybean meal, with some contributions from meat and bone meal, hydrolyzed feather meal, and DL-methionine. Least-cost, linear programming was used to formulate all diets. Protein content of corn and soybean meal, as determined by laboratory analysis, was used in the formulation. Corn and soybean meal protein levels were 8.1 and 47.1%, respectively, for the diets fed from 9 to 12 weeks of age and 8.4 and 48.2% protein, respectively, for diets fed from 12 to 20 weeks of age. Amino acid analyses listed by the National Research Council (1977), adjusted to the appropriate protein concentration of the ingredients, were used to calculate the amino acid concentration of the diets. Diet formulation was done so that the same relative concentrations of total sulfur amino acids (TSAA) and lysine in the protein were maintained within each age interval, irrespective of protein level of the diet. Ingredient composition of the diets, fed from 9 to 12 weeks of age, are presented in Table 2 to illustrate the alterations in ingredient use that occurred with changes in protein and added fat concentrations.
The dietary protein levels tested provided approximately 88, 97, and 107% of the level recommended by National Research Council (1977) for each age interval. The ME concentrations selected represented about 95, 100, and 105% of those commonly used in commercial feeding programs of the central United States. All diets were provided in mash form ad libitum. Body weights were determined at 9, 12, 16, and 20 weeks of age. Feed-consumption data were recorded at 12, 16, and 20 weeks. Records of mortality and causes of mortality were maintained. Approximately 10% of the toms from each pen were processed through the Iowa State University Meats Laboratory, where yield and grade data were obtained. Data were analyzed statistically by the Statistical Analysis System (Barr et al, 1979). RESULTS AND DISCUSSION Dietary ME and protein concentrations each had significant independent effects on gain in body weight and feed efficiency of toms from 9 to 20 weeks of age (Table 3). As each diet variable increased, performance was improved. Increasing dietary ME also reduced the amount of protein consumed per unit of weight gain but had no significant effect on amount of ME consumed per unit of gain. As dietary protein level increased, the amount of protein consumed per gain increased, while the ME consumed per gain decreased. Statistical analysis of data for each production characteristic showed that no significant (P>.10) interaction effect of dietary ME and protein occurred. Dietary protein concentration did not significantly affect carcass yields of the 20week-old toms. Increasing diet ME by adding fat, however, had the significant effect of a slight, inconsistent increase in yields (Table 4). The interaction effect of dietary protein and ME on yield was not significant (P>.10). Similarly, there were no significant main effects of dietary protein or the protein by ME interaction on percent water, protein, or ME in eviscerated carcasses. However, as dietary ME increased, carcass water decreased and carcass fat increased, reflecting a significant (P<.02) main effect of ME. The quantities of fat in the carcass were affected most extensively (Table 4). As dietary ME or protein concentration increased, quantity of carcass fat increased, especially in the instance of ME. Concurrently, amounts of carcass water decreased. There was no significant
22.0
-
.75
.83 .83 .83
.75 .75 .75
.68 .68 .68
(%) •
TSAA
1.35
1.19 1.19 1.19
1.08 1.08 1.08
.97 .97 .97
Lysine
3100
3070 3230 3390
3070 3230 3 390
3072 3232 3392
(kcal/kg)
ME
19.0
20.4 20.4 20.4
18.5 18.5 18.5
16.65 16.65 16.65
Protein i
.65
.72 .72 .72
.65 .65 .65
.59 .59 .59
('/a)
TSAA
12 to 16
Age of t:urkeys, wk
1.00
1.01 1.01 1.01
.92 .92 .92
.83 .83 .83
Lysin
3
2
Laboratory analysis showed that crude protein concentrations of the diets were within .4% of the calculated values
ME = Metabolizable energy, TSAA = total sulfur amino acids, NRC = National Research Council.
An animal-vegetable fat blend, which was analyzed to contain an MIU of 3.8% and the following fatty acid as C 1 6 : , , 2 . 5 ; C I 8 , 8 . 8 ; C J 8 : I , 3 0 . 4 ; C 1 8 : 2 , 30.8;C 1 8 : 3 , 3.3;other, 3.3.
NRC (1977)
3000
0 4 8
High High High
23.1 23.1 23.1
0 4 8
Medium Medium Medium
18.9 18.9 18.9
2970 3130 3290
2975 3135 3295
0 4 8
Low Low Low
21.0 21.0 21.0
(kcal/kg)
(%)
9 to 12
Protein 3
2970 3130 3295
ME2
Protein
Supplemental fat 1
TABLE 1. Selected characteristics of the dietary treatments
2975 19.2 .97 .68 .42 1.20 .74
.10
66.98 21.12 5.34 4.00 .12 .93 .81 .30 .30
Low 0
3135 19.1 .97 .68 .40 1.20 .75
61.49 23.64 2.15 4.00 1.14 1.26 1.66 .30 .30 4.00 .06
Low 4
3295 19.2 .99 .70 .43 1.20 .75
55.27 26.08 2.00 4.50 .45 1.24 1.73 .30 .30 8.00 .13
Low 8
2970 21.4 1.08 .75 .44 1.20 .75
.09
64.32 24.22 6.00 2.16 1.10 .92 .59 .30 .30
Medium 0
3130 20.9 1.08 .75 .43 1.20 .74
58.81 24.14 6.00 3.50 1.39 .87 .60 .30 .30 4.00 .09
(ni \
Medium 4
3
M 8
2
The mineral premix contributed the following per kilogram of diet: manganese, 70 mg; zinc, 40 mg; iron, 37 mg; co
' T h e vitamin premix contributed the following per kilogram of diet; vitamin A, 5000 IU; vitamin D 3 , 1500 IU; v mg; riboflavin, 2.7 mg; pantothenic acid, 7 mg; niacin, 75 mg; choline, 509 mg; folacin, .55 mg; biotin, 75 /xg.
Calculated analysis Metabolizable energy, kcal/kg Protein, by analysis, % Lysine, % Total sulfur amino acids, % Methionine, % Calcium, % Total phosphorus, %
Corn (8.1% protein) Soybean meal (47.1% protein) Meat and bone meal (50% protein) Dehydrated alfalfa meal (17% protein) Hydrolyzed feather meal Ground limestone Dicalcium phosphate Vitamin premix 1 Mineral premix 2 Animal-vegetable fat DL-Methionine
Protein level added fat, %
TABLE 2. Ingredient composition of diets fed from 9 to 12 weeks of
DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS
1531
TABLE 3. Influence of supplemental fat and dietary protein on performance of torn turkeys From 9 to 20 wk of age Dietary ME
Body weight
Low1 Low Low
Low Medium High
Medium Medium Medium
HI
Dietary protein
Weight gain
Feed/ gain
Protein/ gain
ME/gain
12.31 12.35 12.65
8.57 8.60 8.90
3.73 3.49 3.33
(kg/kg)
(Mcal/kg)
.61 .57 .54
11.51 11.33 11.35
Low Medium High
12.17 12.94 12.55
8.38 9.05 8.74
3.71 3.43 3.30
.67 .62 .59
11.43 11.10 11.22
Low Medium High
12.64 12.79 13.09
8.83 9.02 9.28
3.53 3.30 3.18
.70 .65 .63
10.89 10.71 10.82
.34
.11
.02
.36
(*%>
Standard deviation of means Source of variation ME Protein ME X protein 1
Probabilities of significance .03 .04 .30
.001 .002 .98
.001 .001 .98
.30 .001 .99
Protein and metabolizable energy (ME) concentrations of diets for each age interval are shown in Table 1.
interaction effect between dietary ME and protein on quantities of water or fat in the carcass. Quantities of protein in carcasses increased as dietary ME increased. This main effect of ME was significant (P<.05). However, there was an indication of dietary ME by protein interaction effect (P<.07), seemingly as a result of the greater influence of ME on carcass protein, when fed in conjunction with higher levels of protein. The changes in carcass composition of turkeys in this research, related to increasing dietary ME, correspond with those observed by Salmon and O'Neil (1971) and Webb et al. (1975). More recently, Hasiak (1985) described the increases in fat content of different parts of carcasses of turkeys, fed levels of added dietary fat ranging from 2 to 8%. In all instances, there was a linear relationship between dietary fat and ME, and fat in parts of the carcass. The main effect of dietary protein, the absolute increase in quantity of carcass fat, also agrees with earlier reports. Summers (1983) presented data showing that carcass fat of turkeys increased as dietary protein level
increased. Salmon (1984) indicated that an increase in dietary protein fed to broiler turkeys tended to increase "fat score" of the carcasses, although there was little effect on abdominal fat pad. The favorable effect of ME on quantities of carcass protein suggests that this source of additional energy augmented true growth. Also, the ME by protein interaction effect on quantities of carcass protein indicates that the extent of the effect of ME was contingent, in part, on dietary protein level. The proportion of parts in the eviscerated carcasses and the percentage of meat, skin, and bone contained in breasts and thighs are shown in Table 5. In most instances, dietary ME and protein did not significantly (P>.10) affect these carcass traits. However, ME level of the diet altered the percentage of meat and skin (P«.003 and P<.07, respectively) in the breast. These effects of ME were inconsistent; meat of the breast was increased by the intermediate level of ME but was not changed by the high level of ME, whereas skin of the breast decreased slightly with the intermediate ME level
1532
SELL ET AL. TABLE 4. Influence of supplemental fat and dietary protein on yield and composition of eviscerated carcasses of Large White male turkeys
Dietary protein
Dietary ME
Carcass yield
Water
(% of live weight) Low Low Low
1
Protein
Fat
Water
Protein
Fat
(kg carcass)
(% of carcass)
Low Medium High
81.65 83.15 79.88
65.53 65.35 64.70
19.52 19.68 19.02
10.95 11.60 12.45
8.06 8.07 8.18
2.40 2.43 2.41
1.35 1.43 1.58
Medium Medium Medium
Low Medium High
81.72 82.30 82.65
65.45 64.38 64.32
19.00 19.02 19.24
12.00 12.38 12.95
7.97 8.33 8.07
2.31 2.46 2.41
1.46 1.60 1.62
High High High
Low Medium High
80.91 83.24 80.91
65.50 65.25 64.08
19.18 19.51 19.10
11.48 11.80 13.20
8.28 8.34 8.39
2.42 2.50 2.50
1.45 1.51 1.73
1.39
.91
.56
1.08
.28
.11
.14
.05 .33 .07
.01 .02 .92
Standard deviation of means Source of variation ME Protein ME X protein 1
Probabilities of significance .02 .40 .13
.02 .46 .72
.47 .38 .55
.02 .23 .93
.09 .08 .14
Protein and metabolizable energy (ME) concentrations of diets for each age interval are shown in Table 1.
and increased notably with the high ME level. A protein effect (P<.06) was noted only with the proportion of bone in the thigh; proportion of bone was increased when the high protein diets were fed. There was no significant (P».10) interaction effects of dietary ME and protein on proportions of parts in carcasses. Total mortality during the 9 to 20-week age interval was 5.9%. More than 50% of the deaths were the result of aortic and(or) renal hemorrhage. Mortality was uniformly distributed among diet treatment groups. The results of this experiment support previous observations made with turkeys that dietary ME and protein exert independent effects on growth and feed efficiency. Also, the data show that there were no significant interaction effects between dietary ME and protein, with respect to turkey performance, even though a relatively wide range of ME and protein levels were tested. Balloun et al. (1959), working with poults from hatch to 6 weeks of age, found that the interaction effects between dietary ME and protein were negligible as compared with the main effects of each. Jensen et al. (1970) and Waibel (1978) reported similar findings after
feeding diets of various ME and protein contents to growing-finishing turkeys. Sell and Owings (1981) also were unable to detect ME X protein interaction effects on growth and feed efficiency of turkeys from hatch to 20 weeks of age. The absence of significant ME X protein interaction effects on growth and feed efficiency, in experiments designed to detect these effects, raises a question about the relevance of the commonly-accepted concept of "optimum energy to protein ratio." Balloun et al. (1959) stated that the ratio of dietary energy and protein was of relatively minor importance in determining the performance of young turkeys. Recently, Pesti and Fletcher (1983) evaluated a large amount of data obtained with broiler chickens and also found that differences in energy-to-protein ratios of diets was of secondary importance to dietary energy or protein concentrations per se for explaining variation in growth rate or carcass composition. In the current research, a relatively wide range of ME-to-protein ratios was tested within each age interval (Table 6). Regression analysis of the data showed that neither weight gains nor feed
DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS
1533
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DIETARY METABOLIZABLE ENERGY AND PROTEIN FOR TURKEYS efficiencies by poults, within any of the three age intervals, were related significantly with ME-to-protein ratios of the diets (Table 6). Correlation coefficients between ME-to-protein ratios and weight gain ranged from .06 to .28 across age intervals, while those for feed efficiency varied from .03 to .10. Data on carcass composition obtained from the current research indicated that a ME protein interaction may affect absolute amounts of protein in turkey carcasses, and this deserves further investigation. Also, in view of potential importance to further processing of turkey parts, the effects of dietary ME on proportions of meat and skin in the breast should be given consideration in future research. From a practical point of view, data from this experiment and results of other research suggest that the use of "optimum ME-to-protein ratios" as a guideline for ration formulation for growing turkeys may be inappropriate. Use of optimum ME-to-protein ratios may place an unnecessary, costly constraint on formulation. It seems more appropriate to place greater emphasis on the nutritional and economic implications of the independent effects of dietary ME and dietary protein on growth, feed efficiency, and carcass composition of turkeys and to minimize the concern about optimum ME-to-protein ratios.
REFERENCES Balloun, S. L., W. J. Owings, J. L. Sell, and R. E. Phillips, 1959. Energy and protein requirements for turkey starting diets. Poultry Sci. 38:1328— 1340. Barr, A. J., J. H. Goodnight, J. P. Sail, W. H. Blair, and D. M. Chilko, 1979. SAS User's Guide. J. T. Helwig and K. A. Council, ed. SAS Inst., Inc., Raleigh, NC. Combs, G. F., and G. L. Romoser, 1955. A new approach to poultry feed formulation. Maryland Agric. Exp. Stn. Misc. Publ. 226. Day, E. J„ and J. E. Hill, 1957. The effect of calorie: protein ratio of the ration on growth and feed efficiency of turkeys. Poultry Sci. 36:773-779. Hasiak, R. J., 1985. Effect of supplemental dietary fat and growing season on the yield and composition
1535
of torn turkeys. Poultry Sci. 64: (in press). Jensen, L. S., G. W. Schumaier, and J. D. Latshaw, 1970. Extra-caloric effect of dietary fat for developing turkeys as influenced by calorie: protein ratio. Poultry Sci. 49:1697-1704. National Research Council, 1977. Nutrient Requirements of Poultry. 7th ed. Natl. Acad. Sci., Washington, DC. Owen, J. A., P. W. Waldroup, C. J. Mabray, and P. J. Slagter, 1981. Response of growing turkeys to dietary energy levels. Poultry Sci. 60:418—424. Owings, W. J., and J. L. Sell, 1982. Performance of growing turkey hens as influenced by supplemental dietary fat and different ME:nutrient ratios. Poultry Sci. 61:1897-1904. Pesti, G. M., and D. L. Fletcher, 1983. The response of male broiler chickens to diets with various protein and energy contents during the growing phase. Br. Poult. Sci. 24:91-99. Potter, L. M., J. R. Shelton, and L. G. Melton, 1974. Zinc bacitracin and added fat in diets of growing turkeys. Poultry Sci. 53:2072-2081. Salmon, R. E., 1984. Effect of grower and finisher protein on performance, carcass grade, and meat yield of turkey broilers. Poultry Sci. 63:1980— 1986. Salmon, R. E., and J. B. O'Neil, 1971. The effect of the level and source of dietary fat on the growth, feed efficiency, grade, and carcass composition of turkeys. Poultry Sci. 50:1456-1467. Sell, J. L., and W. J. Owings, 1981. Supplemental fat and metabolizable-to-nutrient ratios for growing turkeys. Poultry Sci. 60:2293-2305. Sell, J. L„ and W. J. Owings, 1984. Influence of feeding supplemental fat by age sequence on the performance of growing turkeys. Poultry Sci. 6 3 : 1184-1189. Summers, J. E., 1983. Carcass composition of the heavy turkey. Turkeys 31(2): 3 0 - 3 1 . Sunde, M. L., 1954. The use of animal fats in poultry feeds. J. Am. Oil Chem. Soc. 31:49-52. Touchburn, S. P., and E. C. Naber, 1966. The energy value of fats for growing turkeys. Pages 190— 195 in Proc. 13th World's Poult. Congr., Kiev, USSR. Waibel, P. E., 1958. Effectiveness of unknown growth factors, antibiotic, and animal fat in turkey poult rations. Poultry Sci. 37:1144-1149. Waibel, P. E., 1978. Studies on protein and energy requirements of turkeys during the growing period. Pages 143—154 in Proc. 39th Minnesota Nutr. Conf., Univ. Minnesota, St. Paul, MN. Webb, J. E., J. D. Yates, and C. C. Brunson, 1975. Effect of dietary variables on turkey fat quantity, quality, and stability. Poultry Sci. 54:1349. (Abstr.)