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Effect of Severity of Early Protein Restriction on Large Turkey Toms.
Effect of Severity of Early Protein Restriction on Large Turkey Toms. 2. Carcass Characteristics 1 P. R. FERKET2 and J. L. SELL Department of Animal Science, Iowa State University, Ames, Iowa 50011 (Received for publication March 1, 1988)
1989 Poultry Science 68:687-697 INTRODUCTION
There has been considerable interest in the potential of early protein restriction for practical turkey feeding programs. The advantages of early protein restriction for the efficient use of dietary protein has been documented (Auckland et al., 1969; Auckland and Morris, 1971a,b; Ferket, 1987; Ferket and Sell, 1989). Furthermore, early protein restriction may reduce the incidence of leg weakness near market age (Stevens and Salmon, 1987; Ferket and Sell, 1989). However, there is evidence indicating that large type turkey toms have a limited ability to exhibit a classical compensatory growth response whereby full recovery of body weight is achieved within the desired time period (Auckland, 1972; Ferket, 1987; Ferket and Sell, 1989). Also, the extent of
'Journal Paper Number J-12936 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project Number 2577. 2 Address correspondence to P. R. Ferket, Department of Poultry Science, North Carolina State University, Raleigh, NC 27695-7608.
recovery from early growth restriction is dependent upon the severity of the restriction imposed (Wilson and Osbourn, 1960; Johnson and Sell, 1976). Ferket and Sell (1989) reported the effects of severity of early protein restriction on the performance characteristics of large turkey toms. Toms were fed diets containing 100, 80, 70, or 60% of the National Research Council (NRC, 1984) recommendations for protein from 1 to 6 wk of age and subsequently were fed according to NRC (1984) dietary recommendations. Body weight at 6 wk of age decreased as the severity of protein restriction increased; this relationship persisted until 20 wk of age: weight gains among treatment groups were not significantly different from 6 to 20 wk of age. Attractive features of the results were an increase in overall protein efficiency and decrease in the incidence of leg weakness near market age as the level of early protein nutrition decreased. Carcass characteristics are important factors to consider in the evaluation of alternative feeding programs. Ferket (1987) reported that early protein restriction may influence the proportionality of key tissues and organs.
687
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ABSTRACT The effect of early protein (Pr) nutrition on the carcass characteristics of turkey toms was studied. Four levels of dietary protein [100, 80, 70, or 60% of National Research Council (NRC) recommendations in 1984] were fed as isocaloric diets ad libitum from 1 to 6 wk of age. Subsequently, the four treatment groups were fed according to NRC recommendations in 1984 to 20 wk of age. Toms from all treatment groups were sampled at 6,12, and 20 wk of age, and New York-dressed carcasses were evaluated for chemical composition and yield of commercial cuts. Fat and DM content in the carcass increased, whereas ash and crude Pr content decreased as the toms aged. Yields of breast and back increased, drumsticks and wings decreased, and thighs did not change as the toms aged. At 6 wk, percentages of carcass Pr and ash were not affected by Pr, but fat increased linearly as the level of Pr decreased (P<.005). Breast and thigh meat yields decreased, and skin yield increased as the level of Pr decreased. Yields of bone and other carcass parts were not influenced by Pr. At 12 and 20 wk, breast and thigh meat yields and chemical composition were restored to normal proportions, irrespective of early Pr nutrition. At 20 wk of age, only breast yield was significantly reduced by 60% Pr (P<.05). The amount of dietary Pr consumed per carcass Pr gain decreased at all stages of growth as the level of Pr decreased. Early Pr had minimal effects on relative organ weights. Toms recover from the effects of early Pr restriction on carcass parts, but restriction to the 60% level may reduce breast meat yield. (Key words: turkey toms, early protein restriction, carcass characteristics, compensatory growth)
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FERKET AND SELL
Concurrent with the recording of live performance data (Ferket and Sell, 1989), carcass characteristics, as influenced by the severity of early protein restriction, were determined and are reported herein. MATERIALS AND METHODS
RESULTS AND DISCUSSION
Performance Characteristics. Ferket and Sell (1989) described the live performance of the toms employed in this experiment. In summary, as the level of dietary protein decreased, body weight at 6 wk decreased [2.23, 1.94, 1.63, and 1.39 kg for 100, 80, 70, and 60% of NRC (1984) protein recommendations, respectively (P<.005)], and feed:gain ratios from 1 to 6 wk of age increased (1.63, 1.73, 1.90, and 2.16, respectively, P<.005). Early protein restriction continued to have a significant carry-over effect on absolute body weight, i.e., restricted toms were lighter in weight at 20 wk of age than were tfiose fed 100% of the NRC (1984) recommended protein level. Feed:gain ratios during the 6 to 20-wk realimentation period improved linearly as the level of early protein nutrition decreased (3.25, 3.20, 3.14, and 3.13, P<.005), but cumulative feed:gain ratios from 1 to 20 wk of age were not affected by early protein nutrition (3.02, 3.02, 3.01, and 3.05, respectively, P> .05). Carcass Composition. Proximate analyses of the carcasses of toms sampled at 6, 12, and 20 wk of age are shown in Table 1. In general,
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Large White Nicholas male poults were reared to 1 wk of age on a starter diet approximating NRC (1984) recommendations. Subsequendy the poults were randomly distributed among 32 floor pens of 28 birds each; 8 replicate pens were assigned to each of four dietary treatments. From 1 to 6 wk of age, toms were fed isocaloric diets containing 100, 80, 70, or 60% of the NRC (1984) recommended level of dietary protein. Subsequently, all treatment groups were fed according to NRC (1984) recommendations until 20 wk of age. All diets were available to the toms ad libitum in mash form. Experimental design and management practices are described in detail by Ferket and Sell (1989). Body weight and feed consumption data were recorded at 3, 6, 8, 10, 12, 16, and 20 wk of age. At 6, 12, and 20 wk of age, two toms were sampled from each pen for carcass evaluation. Toms were weighed, fasted for 18 h and then weighed to determine shrinkage. The toms were stunned electrically and killed by exsanguination. Toms were immersed in 60 C water for 2 min, deplumed, weighed, and chilled in ice water for 20 h. Toms were removed from the chill tanks and weighed. Then they were eviscerated, and the weights of liver, heart, gizzard, and intestines were recorded. The eviscerated carcasses were separated into the component parts of breast, thigh, drumsticks, wings, and back. Breast and thighs were further separated into meat, skin, and bone. All the parts of a turkey carcass were put together in a plastic bag after weighing. The carcasses were then stored at -20 C until time of grinding, blending, and proximate analysis. Grinding of carcasses and sample preparation for proximate analysis were performed in the following manner: frozen turkey carcasses were cut into sections by using a band saw (Butcher Boy 0299, Laser Manufacturing Co., Inc., Des Moines, IA) and passed through a mechanical grinder (Buffalo 66BX, Enterprise, Inc., address unknown) three times: first through a 2.5-cm die, then through a .7-cm die, and finally through a .3-cm die to get adequate
mixing and the desired consistency. A 300-g sample was taken from each replicate batch consisting of two turkeys. Two 4-g subsamples from each of these samples were placed in an oven at 100 C for 48 h to determine dry-matter content and then heated to 600 C in a muffle oven for 12 h to obtain ash content. Two 4-g subsamples of each carcass were oven-dried at 70 C for 48 h and extracted with ethyl emer to determine fat content. Finally, two 10-g subsamples were processed to determine crude protein (Kjeldahl N) content by the Nesslerization procedure using the Hach method (Hach Co., Loveland, CO) as described by Ferket (1987). All data were analyzed statistically according to the general linear model procedure for the analysis of variance and regression analysis (SAS, 1982). A completely randomized block design was used, with the experimental unit consisting of the pen averages. Pens on both halves of two houses were blocked. Carcass data obtained at 6 wk of age were evaluated for the direct effect of protein nutrition. Subsequent carcass data were evaluated for the carry-over effect of early protein nutrition.
h).
Dry matter Protein4 Fat Ash Dry matter Protein Fat Ash Dry matter Protein Fat Ash
Measurement
26.9 18.4 1.7 3.9 31.4 18.1 6.8 3.2 35.2 16.4 12.0 2.9
100
34.3 16.6 11.4 3.1
27.3 18.2 2.3 3.7 31.5 18.1 6.8 3.2
80 27.6 18.2 3.4 3.9 31.3 18.2 6.5 3.8 34.8 16.4 11.9 2.9
70
(%)28.0 17.9 3.7 3.9 30.8 18.1 6.3 3.3 35.4 16.9 12.1 2.9
60 .18 .23 .19 .15 .25 .17 .30 .21 .62 .52 .84 .11
SEM3
Crude protein as determined by the Hach method (Hach Co., Loveland, CO).
df = 25.
NRC = National Research Council.
***P<.005.
4
3
2
'Means of eight samples each being ai pooled composite of two toms. The values are expressed as a percentage of wet sa
20 wk
12 wk
6 wk
Age
Dietary protein, % of NRC requirement2
TABLE 1. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass composition of la
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690
FERKET AND SELL
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toms (New York-dressed carcass) underwent realimentation (Table 1). Other researchers considerable change in body composition as have also shown that early protein-restricted they grew older. Fat and dry matter concentra- toms were able to achieve normal body tion in the body increased, whereas body ash composition by market age (Auckland and concentrations decreased as the age of the toms Morris, 1971b; Yates et al., 1976; Ferket, increased. Crude protein concentration, howev- 1987). Conversion of Dietary Protein to Body er, remained about the same at 6 and 12 wk of age, but then decreased by about 1.6 percent- Protein. The treatment effects observed in age units at 20-wk of age. Ferket (1987) body composition over age indicated that early observed similar changes in body composition protein restriction may alter energy metaboas toms aged, but he observed higher carcass lism. Percentage body fat content at 6 wk of protein concentrations than found in the age increased as the level of protein nutrition present experiment, especially in the carcasses decreased during the restriction period, but of 20- wk-old toms. Differences between the upon realimentation, body fat content returned Kjeldahl and Hoch methods used to determine to normal proportions. carcass crude protein may explain the differThe level of early protein nutrition had a ences observed in the results reported by significant influence on protein conversion Ferket (1987) and the present experiment. (Table 2). During the restriction period (1 to 6 Level of protein nutrition had a significant wk of age), dietary protein consumption effect on the composition of carcasses of toms decreased linearly as the level of early protein sampled at 6 wk of age (Table 1). Fat and dry nutrition decreased, and this effect carried over matter concentration in the body increased through the realimentation period. The total linearly by about .5 and .27 percentage units, amount of body protein accretion between 6 respectively, per 10% decrement in the plane and 12 wk of age also decreased as the level of of protein nutrition. Comparison of the body dietary protein decreased. The decrease in fat and dry matter contents suggests that about protein consumption, and thus reduced body half of the increase in body fat was at the protein accretion during this period, was likely expense of body water. Percentage crude due to the lower feed consumption and die protein and ash content at 6 wk of age were smaller body weights for the birds fed the low not influenced significantly by the level of protein diets than those fed the higher protein early protein nutrition. Auckland and Morris diets. At 20 wk of age, however, total body (1971b) and Ferket (1987) also reported that protein content of the protein-restricted toms protein restriction increased fat and dry matter was equal to that of the unrestricted toms, content significantly without affecting crude giving evidence to some compensatory body protein or ash content in the carcasses of toms. protein accretion. Ferket and Sell (1989) showed that the caloric In general, protein consumed by the prointake per kilogram body weight gain of the tein-restricted toms was deposited into die toms reported herein increased as the severity carcass more efficiendy, regardless of the age of protein restriction increased, whereas pro- period. These data are in agreement witii the tein intake per kilogram body weight gain data reported by Ferket (1987). In the present decreased. Evidently, toms consumed an ex- experiment, the amount of dietary protein cessive amount of energy while trying to meet required per kilogram body protein gained protein requirements. Consequently, this ex- during the 1 to 6-wk restriction period cess energy was deposited as body fat. Bartov decreased about 5% for each 10% decrement and Bornstein (1976) made similar observa- in the level of protein nutrition down to the tions when broiler chickens were fed low 70% level. No additional advantage in protein protein diets. conversion was observed by restricting protein Although the level of early protein restric- to die 60% level. During the initial stage of tion had highly significant carry-over effects realimentation, all levels of early protein on body weight and feed efficiency, carry-over restriction were equally effective in improving effects on carcass composition were minimal. protein conversion. During the latter stage of Treatment effects on body composition ob- realimentation, however, protein conversion served at 6 wk of age were no longer evident was improved linearly as the level of early at 12 and 20 wk of age, indicating that normal protein nutrition decreased. Consequently, probody composition had been restored upon tein conversion from 1 to 20 wk of age
'NRC = National Research Council.
.96 3.02 4.59 7.61 8.57 .03 .41 1.47 2.53 2.41 2.85 4.33 3.59 3.43
100
2.10 2.60 4.15 3.46 3.30
.72 2.95 4.57 7.52 8.23 .03 .35 1.42 2.52
80 .56 2.79 4.56 7.35 7.92 .03 .29 1.35 2.45 1.99 2.63 4.14 3.40 3.27
70 .48 2.69 4.54 7.23 7.70 .03 .24 1.27 2.45 2.00 2.61 3.85 3.27 3.18
60
Means of eight samples each, being a pooled composite of two torn carcasses (New York dressed).
***P<.005.
**P<.01.
*P<.05.
4
'Means of eight replicates of ca. 28 toms/replicate.
df = 25.
2
to 6 wk to 12 wk to 20 wk to 20 wk to 20 wk wk wk wk wk to 6 wk to 12 wk to 20 wk to 20 wk to 20 wk
Age period
1 6 12 6 1 Carcass protein, kgAom" 1 6 12 20 Protein consumption xarcass protein gain 1 6 12 6 1
3
Protein consumption, kg/tom
Measurement
Dietary protein, % of NRC requirement1 .00 .02 .04 .07 .07 .00 .00 .01 .07 .03 .05 .10 .08 .08
SE
TABLE 2. Ejfect of severity of early (1 to 6 weeks of age) protein restriction on protein consumption, carcass
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FERKET AND SELL
absolute weights of these parts were still less than those from unrestricted toms. At 20 wk of age, toms subjected to the 60% level of restriction during early development had significantly lower breast yields than toms that were less severely restricted (Table 5). Otherwise, body proportionality was normal for all treatments. Organ Size. Early protein restriction had minimal effects on relative organ weights (Table 6). At 6 wk of age, the relative weight of the liver increased linearly as the level of protein nutrition decreased, whereas relative weights of the gizzard, intestines, and heart were unaffected. In comparison, Ferket (1987) reported that early protein restriction to 70% of NRC (1984) recommendations caused a significant increase in the relative weights of liver, gizzard, and intestine at 6 wk of age. The increase in liver weight observed by Ferket (1987) and in the present experiment was possibly due to an increase in Hpogenesis and fat content associated with dietary protein restriction. Fat content of livers was not determined in this experiment, but the most severely restricted toms had yellowish colored livers characteristic of fatty liver. Relative liver size, hepatic hpogenesis, and percentage of body fat content have been shown to increase in poultry as dietary protein decreases (Yeh and Leveille, 1969; Rosebrough and Steele, 1985). By 12 wk of age, the liver was back to normal proportions, and this state persisted until 20 wk of age. Relative weight of the gizzard and intestines continued to be unaffected by early protein restriction at 12 and 20 wk of age. Restricting protein to the 70 or 60% level, however, resulted in a significant increase in the relative weight of the heart at 12 wk of age, but this effect was not so evident by 20 wk of age. The transient carry-over effects of early protein restriction on relative heart size cannot be explained on the basis of information obtained herein. The results of this experiment are consistent with the contention that toms respond favorably to early protein restriction (Auckland et al., 1969; Auckland and Morris, 1971a,b; Ferket, 1987). This advantage is not necessarily due to a compensatory growth response after early protein restriction, but rather due to an improvement in the efficiency with which dietary protein is utilized for growth. Even though body weight at 20 wk of age decreased as the severity of early protein restriction
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improved linearly as the level of early protein nutrition decreased. Carcass Yield. Early protein nutrition did not influence the degree of body weight shrinkage during the 18-h fast before slaughter or the degree of water taken up by the carcass during the 20-h ice-water chilling, irrespective of the age of the toms sampled. The effect of age on carcass yield can be seen by comparing the values in Tables 3, 4, and 5. As the toms grew older, dressed yield increased, which was largely attributed to increases in yield of breast meat. Concurrently, yield of the thighs did not change, yields of drumsticks and wings decreased, and yield of the back increased as the toms aged. The relationships between age and yield of carcass parts observed in this experiment are in general agreement with those in the literature. Breast yield (as a percentage of eviscerated carcass weight without giblets and neck) has been shown to increase with age, whereas drumstick and wing yield decrease (Salmon, 1974; 1983; Wesley et al., 1981; Salmon et al., 1982). However, data in the literature on yield of thigh meat vary. Yield of thigh meat has been reported to decrease (Salmon, 1974; Wesley et al., 1981), stay the same (Hasiak, 1978), or increase (Salmon, 1974) with increasing age. The data reported herein show a positive relationship between yield of thigh meat and age of toms, irrespective of early protein nutrition. The increase in breast and thigh meat yield with age observed in the present experiment was independent of the level of early protein nutrition. However, early protein restriction evidently affected the development of the major meat-yielding parts of the carcass (breast and thigh) without affecting the development of other carcass parts. At 6 wk of age, the proportion of the breasts and thighs decreased as the level of protein nutrition decreased (Table 3). This decrease was largely attributed to a decrease in yields of breast and thigh meat as a percentage of the New York-dressed carcass. Proportions of skin on the breast and thigh increased as the level of protein nutrition decreased; this was likely related to subcutaneous fat deposition. The yields of drums, wings, and backs, which yield less meat than breasts and thighs, were not influenced by the level of protein nutrition. The breasts and thighs of the protein-restricted toms returned to normal proportions by 12 wk of age (Table 4), but
100
68.5 9.6 21.8 11.1 70.6 8.1 24.5 10.8 13.1 13.5 72.3
70.2 8.4 21.5 11.9 73.1 6.1 20.3 11.5 13.5 14.4 76.1
71.5 7.9 18.6 11.8
73.2 5.9 20.7 10.9 12.9 13.9 74.8
.52 .32 1.70 .22 .35 .32 1.55
.70 .25 1.10 .24
.08 .42
1.34 23.8
1.59 24.8
1.82 25.3
SEM3
60
70
80
NS NS NS NS NS
*** ***
*
NS
* ***
*** ***
Pro
NRC = National Research Council.
df = 25.
***P<005.
**P<.01.
*P<.05.
Yield of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
2
"Means of eight samples each representing the values of two toms. The values are expressed as a percentage of chilled w unless indicated otherwise.
Chilled weight, kg 2.00 25.7 Breast, % % of breast Meat 70.8 Skin 7.7 20.1 Bone 12.1 Thighs, % % of thighs 73.8 Meat Skin 5.5 20.3 Bone 11.0 Drumsticks, % Wings, % 12.8 Back, % 13.3 Dressed yield, %* 74.9
Measurement
Dietary protein, % of NRC requirement2
TABLE 3. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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100
75.5 8.1 16.2
75.8 8.5 15.8 11.5
77.4 5.2 11.1 11.5 18.3 83.3
7.38 29.7
7.78 30.9
77.1 4.9 11.6 11.7 18.1 82.6
11.5
70
80
.39 .14 .12 .17 .29 1.09
.94 .32 .35 .12
75.2 8.3 16.3 11.6 76.3 4.8 11.2 11.5 17.9 82.7
.12 .39
SEM3
6.96 30.5
60
NS NS NS NS NS NS
NS NS NS NS
NS
***
Pro
df = 25.
***P<.005.
*P<05.
Yicld of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
NRC = National Research Council.
2
'Means of eight samples eachrepresentingthe values of two toms. The values are expressed as a percentage of chilled w unless indicated otherwise.
77.3 5.0 11.4 Drumsticks, % 11.6 Wings, % 18.5 Back, % Dressed yield, %* 83.5
% of thighs Meat Skin
Chilled weight, kg 7.80 Breast, % 30.4 % of breast Meat 77.1 8.5 Skin 15.7 Bone 11.6 Thighs, %
Measurement
Dietary protein, % of NRC requirement2
TABLE 4. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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10.8 10.3 20.1 87.8
1.09 .28 .32 .15 .16 .39 1.38
.68 .42 .41 .27
77.7 8.5 13.4 12.7 80.8 7.6 11.4
* *
.194 .41
13.65 33.9
NS NS NS
*
NS NS NS
NS NS NS NS
Prote
SEM3
60
df = 25.
**P<.01.
*P<.05.
Yield of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
NRC = National Research Council.
2
'Means of eight samples each representing the values of two toms. The values are expressed as a percentage of chilled we unless indicated otherwise.
80.4 7.3 11.4 10.4 10.3 19.7 87.9
81.0 7.1 10.3 10.7 10.6 19.7 88.4
% of thighs Meat Skin Bone Drumsticks, % Wings, % Back, % Dressed yield, %'
81.1 7.2 11.0 10.3 10.0 19.3 87.8
78.1 8.3 13.0 12.5
78.5 8.0 13.7 13.0
70 14.10 35.0
80
14.15 34.4
100
Chilled weight, kg 14.53 Breast, % 35.8 % of breast Meat 77.0 Skin 9.0 Bone 13.2 12.4 Thighs, %
Measurement
Dietary protein, % of NRC requirement2
TABLE 5. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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100
1.79 3.22 5.06 .65 1.31 1.67 2.82 .55 1.05 1.20 2.05 .41
Measurement
Liver Gizzard Intestine Heart Liver Gizzard Intestine Heart Liver Gizzard Intestine Heart
70 2.19 3.55 5.49 .66 1.41 1.77 2.94 .60 1.11 1.13 1.97 .44
80
2.09 3.15 5.31 .63 1.31 1.65 2.90 .56 1.11 1.13 2.01 .44
(%) 2.30 3.37 5.32 .68 1.36 1.83 2.93 .60 1.08 1.23 2.00 .40
60 .08 .18 .18 .01 .03 .06 .07 .016 .05 .05 .05 .015
SEM3
NRC = National Research Council.
***P<.005.
**P<.01.
*P<05.
df = 25.
3
2
'Means of eight samples each representing the values from two toms. The values are expressed as a percentage of chilled w
Age
Dietary protein, % of NRC requirement2
TABLE 6. Effect of severity of protein restriction from 1 to 6 weeks of age on liver, gizzard, intestine, and heart we
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PROTEIN NUTRITION AND CARCASS YIELD OF TOMS
ACKNOWLEDGMENTS
The financial assistance provided by the Fats and Protein Research Foundation, Des Plaines, IL, and the Iowa Turkey Marketing Council is gratefully acknowledged. Technical help of F. Escribano, S. Scheideler, I. Zatari, R. Angel, B. Rahn, and the ISU Poultry Farm Staff is appreciated. REFERENCES Auckland, J. N., 1972. Compensatory growth in turkeys: Practical implications and limitations. World's Poult. Sci. J. 28:291-300. Auckland, J. N., and T. R. Morris, 1971a. Compensatory growth in turkeys: Effect of undernutrition on subsequent protein requirements. Br. Poult. Sci. 12:42-48. Auckland, J. N., and T. R. Morris, 1971b. Compensatory growth after undernutrition in market turkeys: Effect of low protein feeding and realimentation on body composition. Br. Poult. Sci. 12:137-150. Auckland, J. N., T. R. Morris, and R. C. Jennings, 1969. Compensatory growth after undernutrition in market turkeys. Br. Poult. Sci. 10:293-302.
Bartov, I., and S. Bomstein, 1976. Effect of degree of fatness in broilers and other carcass characteristics: Relationship between fatness and the composition of carcass fat. Br. Poult. Sci. 17:29-38. Ferket, P. R., 1987. The effect of early nutrient restriction on subsequent compensatory growth in market turkeys. Ph.D. Diss. Iowa State Univ., Ames, LA. Ferket, P. R., and J. L. Sell, 1989. Effect of severity of early protein restriction on large turkey toms. 1. Performance characteristics and leg weakness. Poultry Sci. 68: Hasiak, R. J., 1978. Influence of production practices, season, and transportation variables on the yield and grade of torn turkeys. Poultry Sci. 57:1143. (Abstr.) Johnson, R. L., and J. L. Sell, 1976. Compensatory growth. A new production concept. North Dakota Farm Res. 33:17-20. National Research Council, 1984. Nutrient Requirements of Poultry. 8th ed. Natl. Acad. Sci., Washington, DC. Rosebrough, R. W., and N. C. Steele, 1985. Energy and protein relations in the broiler chicken. 2. Effect of varied protein and constant carbohydrate levels on body composition and lipid metabolism. Growth 49: 479-489. Salmon, R. E., 1974. Effect of dietary fat concentration and energy to protein ratio on the performance yield of carcass components and composition of skin and meat of turkeys as related to age. Br. Poult. Sci. 15:543-560. Salmon, R. E., 1983. The effect of energy protein ratio of the diet, strain, and age at slaughter on performance and carcass of dietary protein concentration and frequency of diet changes on rate of growth, efficiency of food utilization and carcass quality of large white turkeys. Br. Poult. Sci. 23:501-517. SAS, 1982. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Stevens, V. I., and R. E. Salmon, 1987. Effect of dietary protein on leg disorders in turkeys. Poultry Sci. 66(Suppl. 1):181. (Abstr.) Wesley, R. D., R. L. Adams, and W. J. Stadelman, 1981. Effects of amino acid restriction and age on weights and meat yields of turkeys. Poultry Sci. 60:1422-1428. Wilson, P. N., and D. F. Osbourn, 1960. Compensatory growth after undernutrition in mammals and birds. Biol. Rev. 35:325-361. Yates, J. D., W. D. Clower, and J. E. Webb, 1976. Influence of low and conventional protein rations for young turkeys upon subsequent performance and carcass composition. Poultry Sci. 55:2109. (Abstr.) Yeh, Y. Y., and G. A. Leveille, 1969. Effect of dietary protein on hepatic lipogenesis in the growing chick. J. Nutr. 98:356-366.
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increased (Ferket and Sell, 1989), conversion of dietary protein to carcass protein improved significantly during the restriction period and during the subsequent realimentation period. The improved protein conversion observed during realimentation was accompanied by a restoration of normal carcass chemical composition, and normal proportionality of body tissues by 20 wk of age, provided that early protein nutrition was not restricted below the 70% level. Restricting dietary protein to 60% of NRC (1984) during early development continued to have a detrimental effect on breast yield at 20 wk of age. Early protein restriction seemed to shift muscle development to a later age, when dietary conditions were more adequate. This alteration in muscle development was evident in the selective effect of early protein restriction on the reduction and subsequent restoration of breast and thigh meat yield.
697
1989 Poultry Science 68:687-697 INTRODUCTION
There has been considerable interest in the potential of early protein restriction for practical turkey feeding programs. The advantages of early protein restriction for the efficient use of dietary protein has been documented (Auckland et al., 1969; Auckland and Morris, 1971a,b; Ferket, 1987; Ferket and Sell, 1989). Furthermore, early protein restriction may reduce the incidence of leg weakness near market age (Stevens and Salmon, 1987; Ferket and Sell, 1989). However, there is evidence indicating that large type turkey toms have a limited ability to exhibit a classical compensatory growth response whereby full recovery of body weight is achieved within the desired time period (Auckland, 1972; Ferket, 1987; Ferket and Sell, 1989). Also, the extent of
'Journal Paper Number J-12936 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project Number 2577. 2 Address correspondence to P. R. Ferket, Department of Poultry Science, North Carolina State University, Raleigh, NC 27695-7608.
recovery from early growth restriction is dependent upon the severity of the restriction imposed (Wilson and Osbourn, 1960; Johnson and Sell, 1976). Ferket and Sell (1989) reported the effects of severity of early protein restriction on the performance characteristics of large turkey toms. Toms were fed diets containing 100, 80, 70, or 60% of the National Research Council (NRC, 1984) recommendations for protein from 1 to 6 wk of age and subsequently were fed according to NRC (1984) dietary recommendations. Body weight at 6 wk of age decreased as the severity of protein restriction increased; this relationship persisted until 20 wk of age: weight gains among treatment groups were not significantly different from 6 to 20 wk of age. Attractive features of the results were an increase in overall protein efficiency and decrease in the incidence of leg weakness near market age as the level of early protein nutrition decreased. Carcass characteristics are important factors to consider in the evaluation of alternative feeding programs. Ferket (1987) reported that early protein restriction may influence the proportionality of key tissues and organs.
687
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ABSTRACT The effect of early protein (Pr) nutrition on the carcass characteristics of turkey toms was studied. Four levels of dietary protein [100, 80, 70, or 60% of National Research Council (NRC) recommendations in 1984] were fed as isocaloric diets ad libitum from 1 to 6 wk of age. Subsequently, the four treatment groups were fed according to NRC recommendations in 1984 to 20 wk of age. Toms from all treatment groups were sampled at 6,12, and 20 wk of age, and New York-dressed carcasses were evaluated for chemical composition and yield of commercial cuts. Fat and DM content in the carcass increased, whereas ash and crude Pr content decreased as the toms aged. Yields of breast and back increased, drumsticks and wings decreased, and thighs did not change as the toms aged. At 6 wk, percentages of carcass Pr and ash were not affected by Pr, but fat increased linearly as the level of Pr decreased (P<.005). Breast and thigh meat yields decreased, and skin yield increased as the level of Pr decreased. Yields of bone and other carcass parts were not influenced by Pr. At 12 and 20 wk, breast and thigh meat yields and chemical composition were restored to normal proportions, irrespective of early Pr nutrition. At 20 wk of age, only breast yield was significantly reduced by 60% Pr (P<.05). The amount of dietary Pr consumed per carcass Pr gain decreased at all stages of growth as the level of Pr decreased. Early Pr had minimal effects on relative organ weights. Toms recover from the effects of early Pr restriction on carcass parts, but restriction to the 60% level may reduce breast meat yield. (Key words: turkey toms, early protein restriction, carcass characteristics, compensatory growth)
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FERKET AND SELL
Concurrent with the recording of live performance data (Ferket and Sell, 1989), carcass characteristics, as influenced by the severity of early protein restriction, were determined and are reported herein. MATERIALS AND METHODS
RESULTS AND DISCUSSION
Performance Characteristics. Ferket and Sell (1989) described the live performance of the toms employed in this experiment. In summary, as the level of dietary protein decreased, body weight at 6 wk decreased [2.23, 1.94, 1.63, and 1.39 kg for 100, 80, 70, and 60% of NRC (1984) protein recommendations, respectively (P<.005)], and feed:gain ratios from 1 to 6 wk of age increased (1.63, 1.73, 1.90, and 2.16, respectively, P<.005). Early protein restriction continued to have a significant carry-over effect on absolute body weight, i.e., restricted toms were lighter in weight at 20 wk of age than were tfiose fed 100% of the NRC (1984) recommended protein level. Feed:gain ratios during the 6 to 20-wk realimentation period improved linearly as the level of early protein nutrition decreased (3.25, 3.20, 3.14, and 3.13, P<.005), but cumulative feed:gain ratios from 1 to 20 wk of age were not affected by early protein nutrition (3.02, 3.02, 3.01, and 3.05, respectively, P> .05). Carcass Composition. Proximate analyses of the carcasses of toms sampled at 6, 12, and 20 wk of age are shown in Table 1. In general,
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Large White Nicholas male poults were reared to 1 wk of age on a starter diet approximating NRC (1984) recommendations. Subsequendy the poults were randomly distributed among 32 floor pens of 28 birds each; 8 replicate pens were assigned to each of four dietary treatments. From 1 to 6 wk of age, toms were fed isocaloric diets containing 100, 80, 70, or 60% of the NRC (1984) recommended level of dietary protein. Subsequently, all treatment groups were fed according to NRC (1984) recommendations until 20 wk of age. All diets were available to the toms ad libitum in mash form. Experimental design and management practices are described in detail by Ferket and Sell (1989). Body weight and feed consumption data were recorded at 3, 6, 8, 10, 12, 16, and 20 wk of age. At 6, 12, and 20 wk of age, two toms were sampled from each pen for carcass evaluation. Toms were weighed, fasted for 18 h and then weighed to determine shrinkage. The toms were stunned electrically and killed by exsanguination. Toms were immersed in 60 C water for 2 min, deplumed, weighed, and chilled in ice water for 20 h. Toms were removed from the chill tanks and weighed. Then they were eviscerated, and the weights of liver, heart, gizzard, and intestines were recorded. The eviscerated carcasses were separated into the component parts of breast, thigh, drumsticks, wings, and back. Breast and thighs were further separated into meat, skin, and bone. All the parts of a turkey carcass were put together in a plastic bag after weighing. The carcasses were then stored at -20 C until time of grinding, blending, and proximate analysis. Grinding of carcasses and sample preparation for proximate analysis were performed in the following manner: frozen turkey carcasses were cut into sections by using a band saw (Butcher Boy 0299, Laser Manufacturing Co., Inc., Des Moines, IA) and passed through a mechanical grinder (Buffalo 66BX, Enterprise, Inc., address unknown) three times: first through a 2.5-cm die, then through a .7-cm die, and finally through a .3-cm die to get adequate
mixing and the desired consistency. A 300-g sample was taken from each replicate batch consisting of two turkeys. Two 4-g subsamples from each of these samples were placed in an oven at 100 C for 48 h to determine dry-matter content and then heated to 600 C in a muffle oven for 12 h to obtain ash content. Two 4-g subsamples of each carcass were oven-dried at 70 C for 48 h and extracted with ethyl emer to determine fat content. Finally, two 10-g subsamples were processed to determine crude protein (Kjeldahl N) content by the Nesslerization procedure using the Hach method (Hach Co., Loveland, CO) as described by Ferket (1987). All data were analyzed statistically according to the general linear model procedure for the analysis of variance and regression analysis (SAS, 1982). A completely randomized block design was used, with the experimental unit consisting of the pen averages. Pens on both halves of two houses were blocked. Carcass data obtained at 6 wk of age were evaluated for the direct effect of protein nutrition. Subsequent carcass data were evaluated for the carry-over effect of early protein nutrition.
h).
Dry matter Protein4 Fat Ash Dry matter Protein Fat Ash Dry matter Protein Fat Ash
Measurement
26.9 18.4 1.7 3.9 31.4 18.1 6.8 3.2 35.2 16.4 12.0 2.9
100
34.3 16.6 11.4 3.1
27.3 18.2 2.3 3.7 31.5 18.1 6.8 3.2
80 27.6 18.2 3.4 3.9 31.3 18.2 6.5 3.8 34.8 16.4 11.9 2.9
70
(%)28.0 17.9 3.7 3.9 30.8 18.1 6.3 3.3 35.4 16.9 12.1 2.9
60 .18 .23 .19 .15 .25 .17 .30 .21 .62 .52 .84 .11
SEM3
Crude protein as determined by the Hach method (Hach Co., Loveland, CO).
df = 25.
NRC = National Research Council.
***P<.005.
4
3
2
'Means of eight samples each being ai pooled composite of two toms. The values are expressed as a percentage of wet sa
20 wk
12 wk
6 wk
Age
Dietary protein, % of NRC requirement2
TABLE 1. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass composition of la
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690
FERKET AND SELL
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toms (New York-dressed carcass) underwent realimentation (Table 1). Other researchers considerable change in body composition as have also shown that early protein-restricted they grew older. Fat and dry matter concentra- toms were able to achieve normal body tion in the body increased, whereas body ash composition by market age (Auckland and concentrations decreased as the age of the toms Morris, 1971b; Yates et al., 1976; Ferket, increased. Crude protein concentration, howev- 1987). Conversion of Dietary Protein to Body er, remained about the same at 6 and 12 wk of age, but then decreased by about 1.6 percent- Protein. The treatment effects observed in age units at 20-wk of age. Ferket (1987) body composition over age indicated that early observed similar changes in body composition protein restriction may alter energy metaboas toms aged, but he observed higher carcass lism. Percentage body fat content at 6 wk of protein concentrations than found in the age increased as the level of protein nutrition present experiment, especially in the carcasses decreased during the restriction period, but of 20- wk-old toms. Differences between the upon realimentation, body fat content returned Kjeldahl and Hoch methods used to determine to normal proportions. carcass crude protein may explain the differThe level of early protein nutrition had a ences observed in the results reported by significant influence on protein conversion Ferket (1987) and the present experiment. (Table 2). During the restriction period (1 to 6 Level of protein nutrition had a significant wk of age), dietary protein consumption effect on the composition of carcasses of toms decreased linearly as the level of early protein sampled at 6 wk of age (Table 1). Fat and dry nutrition decreased, and this effect carried over matter concentration in the body increased through the realimentation period. The total linearly by about .5 and .27 percentage units, amount of body protein accretion between 6 respectively, per 10% decrement in the plane and 12 wk of age also decreased as the level of of protein nutrition. Comparison of the body dietary protein decreased. The decrease in fat and dry matter contents suggests that about protein consumption, and thus reduced body half of the increase in body fat was at the protein accretion during this period, was likely expense of body water. Percentage crude due to the lower feed consumption and die protein and ash content at 6 wk of age were smaller body weights for the birds fed the low not influenced significantly by the level of protein diets than those fed the higher protein early protein nutrition. Auckland and Morris diets. At 20 wk of age, however, total body (1971b) and Ferket (1987) also reported that protein content of the protein-restricted toms protein restriction increased fat and dry matter was equal to that of the unrestricted toms, content significantly without affecting crude giving evidence to some compensatory body protein or ash content in the carcasses of toms. protein accretion. Ferket and Sell (1989) showed that the caloric In general, protein consumed by the prointake per kilogram body weight gain of the tein-restricted toms was deposited into die toms reported herein increased as the severity carcass more efficiendy, regardless of the age of protein restriction increased, whereas pro- period. These data are in agreement witii the tein intake per kilogram body weight gain data reported by Ferket (1987). In the present decreased. Evidently, toms consumed an ex- experiment, the amount of dietary protein cessive amount of energy while trying to meet required per kilogram body protein gained protein requirements. Consequently, this ex- during the 1 to 6-wk restriction period cess energy was deposited as body fat. Bartov decreased about 5% for each 10% decrement and Bornstein (1976) made similar observa- in the level of protein nutrition down to the tions when broiler chickens were fed low 70% level. No additional advantage in protein protein diets. conversion was observed by restricting protein Although the level of early protein restric- to die 60% level. During the initial stage of tion had highly significant carry-over effects realimentation, all levels of early protein on body weight and feed efficiency, carry-over restriction were equally effective in improving effects on carcass composition were minimal. protein conversion. During the latter stage of Treatment effects on body composition ob- realimentation, however, protein conversion served at 6 wk of age were no longer evident was improved linearly as the level of early at 12 and 20 wk of age, indicating that normal protein nutrition decreased. Consequently, probody composition had been restored upon tein conversion from 1 to 20 wk of age
'NRC = National Research Council.
.96 3.02 4.59 7.61 8.57 .03 .41 1.47 2.53 2.41 2.85 4.33 3.59 3.43
100
2.10 2.60 4.15 3.46 3.30
.72 2.95 4.57 7.52 8.23 .03 .35 1.42 2.52
80 .56 2.79 4.56 7.35 7.92 .03 .29 1.35 2.45 1.99 2.63 4.14 3.40 3.27
70 .48 2.69 4.54 7.23 7.70 .03 .24 1.27 2.45 2.00 2.61 3.85 3.27 3.18
60
Means of eight samples each, being a pooled composite of two torn carcasses (New York dressed).
***P<.005.
**P<.01.
*P<.05.
4
'Means of eight replicates of ca. 28 toms/replicate.
df = 25.
2
to 6 wk to 12 wk to 20 wk to 20 wk to 20 wk wk wk wk wk to 6 wk to 12 wk to 20 wk to 20 wk to 20 wk
Age period
1 6 12 6 1 Carcass protein, kgAom" 1 6 12 20 Protein consumption xarcass protein gain 1 6 12 6 1
3
Protein consumption, kg/tom
Measurement
Dietary protein, % of NRC requirement1 .00 .02 .04 .07 .07 .00 .00 .01 .07 .03 .05 .10 .08 .08
SE
TABLE 2. Ejfect of severity of early (1 to 6 weeks of age) protein restriction on protein consumption, carcass
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692
FERKET AND SELL
absolute weights of these parts were still less than those from unrestricted toms. At 20 wk of age, toms subjected to the 60% level of restriction during early development had significantly lower breast yields than toms that were less severely restricted (Table 5). Otherwise, body proportionality was normal for all treatments. Organ Size. Early protein restriction had minimal effects on relative organ weights (Table 6). At 6 wk of age, the relative weight of the liver increased linearly as the level of protein nutrition decreased, whereas relative weights of the gizzard, intestines, and heart were unaffected. In comparison, Ferket (1987) reported that early protein restriction to 70% of NRC (1984) recommendations caused a significant increase in the relative weights of liver, gizzard, and intestine at 6 wk of age. The increase in liver weight observed by Ferket (1987) and in the present experiment was possibly due to an increase in Hpogenesis and fat content associated with dietary protein restriction. Fat content of livers was not determined in this experiment, but the most severely restricted toms had yellowish colored livers characteristic of fatty liver. Relative liver size, hepatic hpogenesis, and percentage of body fat content have been shown to increase in poultry as dietary protein decreases (Yeh and Leveille, 1969; Rosebrough and Steele, 1985). By 12 wk of age, the liver was back to normal proportions, and this state persisted until 20 wk of age. Relative weight of the gizzard and intestines continued to be unaffected by early protein restriction at 12 and 20 wk of age. Restricting protein to the 70 or 60% level, however, resulted in a significant increase in the relative weight of the heart at 12 wk of age, but this effect was not so evident by 20 wk of age. The transient carry-over effects of early protein restriction on relative heart size cannot be explained on the basis of information obtained herein. The results of this experiment are consistent with the contention that toms respond favorably to early protein restriction (Auckland et al., 1969; Auckland and Morris, 1971a,b; Ferket, 1987). This advantage is not necessarily due to a compensatory growth response after early protein restriction, but rather due to an improvement in the efficiency with which dietary protein is utilized for growth. Even though body weight at 20 wk of age decreased as the severity of early protein restriction
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improved linearly as the level of early protein nutrition decreased. Carcass Yield. Early protein nutrition did not influence the degree of body weight shrinkage during the 18-h fast before slaughter or the degree of water taken up by the carcass during the 20-h ice-water chilling, irrespective of the age of the toms sampled. The effect of age on carcass yield can be seen by comparing the values in Tables 3, 4, and 5. As the toms grew older, dressed yield increased, which was largely attributed to increases in yield of breast meat. Concurrently, yield of the thighs did not change, yields of drumsticks and wings decreased, and yield of the back increased as the toms aged. The relationships between age and yield of carcass parts observed in this experiment are in general agreement with those in the literature. Breast yield (as a percentage of eviscerated carcass weight without giblets and neck) has been shown to increase with age, whereas drumstick and wing yield decrease (Salmon, 1974; 1983; Wesley et al., 1981; Salmon et al., 1982). However, data in the literature on yield of thigh meat vary. Yield of thigh meat has been reported to decrease (Salmon, 1974; Wesley et al., 1981), stay the same (Hasiak, 1978), or increase (Salmon, 1974) with increasing age. The data reported herein show a positive relationship between yield of thigh meat and age of toms, irrespective of early protein nutrition. The increase in breast and thigh meat yield with age observed in the present experiment was independent of the level of early protein nutrition. However, early protein restriction evidently affected the development of the major meat-yielding parts of the carcass (breast and thigh) without affecting the development of other carcass parts. At 6 wk of age, the proportion of the breasts and thighs decreased as the level of protein nutrition decreased (Table 3). This decrease was largely attributed to a decrease in yields of breast and thigh meat as a percentage of the New York-dressed carcass. Proportions of skin on the breast and thigh increased as the level of protein nutrition decreased; this was likely related to subcutaneous fat deposition. The yields of drums, wings, and backs, which yield less meat than breasts and thighs, were not influenced by the level of protein nutrition. The breasts and thighs of the protein-restricted toms returned to normal proportions by 12 wk of age (Table 4), but
100
68.5 9.6 21.8 11.1 70.6 8.1 24.5 10.8 13.1 13.5 72.3
70.2 8.4 21.5 11.9 73.1 6.1 20.3 11.5 13.5 14.4 76.1
71.5 7.9 18.6 11.8
73.2 5.9 20.7 10.9 12.9 13.9 74.8
.52 .32 1.70 .22 .35 .32 1.55
.70 .25 1.10 .24
.08 .42
1.34 23.8
1.59 24.8
1.82 25.3
SEM3
60
70
80
NS NS NS NS NS
*** ***
*
NS
* ***
*** ***
Pro
NRC = National Research Council.
df = 25.
***P<005.
**P<.01.
*P<.05.
Yield of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
2
"Means of eight samples each representing the values of two toms. The values are expressed as a percentage of chilled w unless indicated otherwise.
Chilled weight, kg 2.00 25.7 Breast, % % of breast Meat 70.8 Skin 7.7 20.1 Bone 12.1 Thighs, % % of thighs 73.8 Meat Skin 5.5 20.3 Bone 11.0 Drumsticks, % Wings, % 12.8 Back, % 13.3 Dressed yield, %* 74.9
Measurement
Dietary protein, % of NRC requirement2
TABLE 3. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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100
75.5 8.1 16.2
75.8 8.5 15.8 11.5
77.4 5.2 11.1 11.5 18.3 83.3
7.38 29.7
7.78 30.9
77.1 4.9 11.6 11.7 18.1 82.6
11.5
70
80
.39 .14 .12 .17 .29 1.09
.94 .32 .35 .12
75.2 8.3 16.3 11.6 76.3 4.8 11.2 11.5 17.9 82.7
.12 .39
SEM3
6.96 30.5
60
NS NS NS NS NS NS
NS NS NS NS
NS
***
Pro
df = 25.
***P<.005.
*P<05.
Yicld of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
NRC = National Research Council.
2
'Means of eight samples eachrepresentingthe values of two toms. The values are expressed as a percentage of chilled w unless indicated otherwise.
77.3 5.0 11.4 Drumsticks, % 11.6 Wings, % 18.5 Back, % Dressed yield, %* 83.5
% of thighs Meat Skin
Chilled weight, kg 7.80 Breast, % 30.4 % of breast Meat 77.1 8.5 Skin 15.7 Bone 11.6 Thighs, %
Measurement
Dietary protein, % of NRC requirement2
TABLE 4. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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10.8 10.3 20.1 87.8
1.09 .28 .32 .15 .16 .39 1.38
.68 .42 .41 .27
77.7 8.5 13.4 12.7 80.8 7.6 11.4
* *
.194 .41
13.65 33.9
NS NS NS
*
NS NS NS
NS NS NS NS
Prote
SEM3
60
df = 25.
**P<.01.
*P<.05.
Yield of eviscerated carcass without neck, feet, and giblets expressed as a percentage of chilled weight.
4
3
NRC = National Research Council.
2
'Means of eight samples each representing the values of two toms. The values are expressed as a percentage of chilled we unless indicated otherwise.
80.4 7.3 11.4 10.4 10.3 19.7 87.9
81.0 7.1 10.3 10.7 10.6 19.7 88.4
% of thighs Meat Skin Bone Drumsticks, % Wings, % Back, % Dressed yield, %'
81.1 7.2 11.0 10.3 10.0 19.3 87.8
78.1 8.3 13.0 12.5
78.5 8.0 13.7 13.0
70 14.10 35.0
80
14.15 34.4
100
Chilled weight, kg 14.53 Breast, % 35.8 % of breast Meat 77.0 Skin 9.0 Bone 13.2 12.4 Thighs, %
Measurement
Dietary protein, % of NRC requirement2
TABLE 5. Effect of severity of protein restriction from 1 to 6 weeks of age on carcass yield
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100
1.79 3.22 5.06 .65 1.31 1.67 2.82 .55 1.05 1.20 2.05 .41
Measurement
Liver Gizzard Intestine Heart Liver Gizzard Intestine Heart Liver Gizzard Intestine Heart
70 2.19 3.55 5.49 .66 1.41 1.77 2.94 .60 1.11 1.13 1.97 .44
80
2.09 3.15 5.31 .63 1.31 1.65 2.90 .56 1.11 1.13 2.01 .44
(%) 2.30 3.37 5.32 .68 1.36 1.83 2.93 .60 1.08 1.23 2.00 .40
60 .08 .18 .18 .01 .03 .06 .07 .016 .05 .05 .05 .015
SEM3
NRC = National Research Council.
***P<.005.
**P<.01.
*P<05.
df = 25.
3
2
'Means of eight samples each representing the values from two toms. The values are expressed as a percentage of chilled w
Age
Dietary protein, % of NRC requirement2
TABLE 6. Effect of severity of protein restriction from 1 to 6 weeks of age on liver, gizzard, intestine, and heart we
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PROTEIN NUTRITION AND CARCASS YIELD OF TOMS
ACKNOWLEDGMENTS
The financial assistance provided by the Fats and Protein Research Foundation, Des Plaines, IL, and the Iowa Turkey Marketing Council is gratefully acknowledged. Technical help of F. Escribano, S. Scheideler, I. Zatari, R. Angel, B. Rahn, and the ISU Poultry Farm Staff is appreciated. REFERENCES Auckland, J. N., 1972. Compensatory growth in turkeys: Practical implications and limitations. World's Poult. Sci. J. 28:291-300. Auckland, J. N., and T. R. Morris, 1971a. Compensatory growth in turkeys: Effect of undernutrition on subsequent protein requirements. Br. Poult. Sci. 12:42-48. Auckland, J. N., and T. R. Morris, 1971b. Compensatory growth after undernutrition in market turkeys: Effect of low protein feeding and realimentation on body composition. Br. Poult. Sci. 12:137-150. Auckland, J. N., T. R. Morris, and R. C. Jennings, 1969. Compensatory growth after undernutrition in market turkeys. Br. Poult. Sci. 10:293-302.
Bartov, I., and S. Bomstein, 1976. Effect of degree of fatness in broilers and other carcass characteristics: Relationship between fatness and the composition of carcass fat. Br. Poult. Sci. 17:29-38. Ferket, P. R., 1987. The effect of early nutrient restriction on subsequent compensatory growth in market turkeys. Ph.D. Diss. Iowa State Univ., Ames, LA. Ferket, P. R., and J. L. Sell, 1989. Effect of severity of early protein restriction on large turkey toms. 1. Performance characteristics and leg weakness. Poultry Sci. 68: Hasiak, R. J., 1978. Influence of production practices, season, and transportation variables on the yield and grade of torn turkeys. Poultry Sci. 57:1143. (Abstr.) Johnson, R. L., and J. L. Sell, 1976. Compensatory growth. A new production concept. North Dakota Farm Res. 33:17-20. National Research Council, 1984. Nutrient Requirements of Poultry. 8th ed. Natl. Acad. Sci., Washington, DC. Rosebrough, R. W., and N. C. Steele, 1985. Energy and protein relations in the broiler chicken. 2. Effect of varied protein and constant carbohydrate levels on body composition and lipid metabolism. Growth 49: 479-489. Salmon, R. E., 1974. Effect of dietary fat concentration and energy to protein ratio on the performance yield of carcass components and composition of skin and meat of turkeys as related to age. Br. Poult. Sci. 15:543-560. Salmon, R. E., 1983. The effect of energy protein ratio of the diet, strain, and age at slaughter on performance and carcass of dietary protein concentration and frequency of diet changes on rate of growth, efficiency of food utilization and carcass quality of large white turkeys. Br. Poult. Sci. 23:501-517. SAS, 1982. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Stevens, V. I., and R. E. Salmon, 1987. Effect of dietary protein on leg disorders in turkeys. Poultry Sci. 66(Suppl. 1):181. (Abstr.) Wesley, R. D., R. L. Adams, and W. J. Stadelman, 1981. Effects of amino acid restriction and age on weights and meat yields of turkeys. Poultry Sci. 60:1422-1428. Wilson, P. N., and D. F. Osbourn, 1960. Compensatory growth after undernutrition in mammals and birds. Biol. Rev. 35:325-361. Yates, J. D., W. D. Clower, and J. E. Webb, 1976. Influence of low and conventional protein rations for young turkeys upon subsequent performance and carcass composition. Poultry Sci. 55:2109. (Abstr.) Yeh, Y. Y., and G. A. Leveille, 1969. Effect of dietary protein on hepatic lipogenesis in the growing chick. J. Nutr. 98:356-366.
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increased (Ferket and Sell, 1989), conversion of dietary protein to carcass protein improved significantly during the restriction period and during the subsequent realimentation period. The improved protein conversion observed during realimentation was accompanied by a restoration of normal carcass chemical composition, and normal proportionality of body tissues by 20 wk of age, provided that early protein nutrition was not restricted below the 70% level. Restricting dietary protein to 60% of NRC (1984) during early development continued to have a detrimental effect on breast yield at 20 wk of age. Early protein restriction seemed to shift muscle development to a later age, when dietary conditions were more adequate. This alteration in muscle development was evident in the selective effect of early protein restriction on the reduction and subsequent restoration of breast and thigh meat yield.
697