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Relationships Among Major Body Components of Broiler Chicks1
Relationships Among Major Body Components of Broiler Chicks' M.S. WOLYNETZ Engineering and Statistical Research Centre, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6 I. R. SIBBALD Animal Research Centre, Agriculture Canada, Ottawa, Ontario, Canada KIA0C6 (Received for publication July 22, 1985)
1986 Poultry Science 65:2324-2329 INTRODUCTION
Measurement of the major chemical components of chicks (water, protein, fat, ash), as well as energy, is laborious and requires the use of equipment that may not be readily available. Prediction equations have been developed to simplify estimation of body composition, but the scope of such equations is generally limited. Summers and Fisher (1961) observed relatively constant watennitrogen ratios among the carcasses of chickens within experiments and proposed that the ratio, measured in chicks of one replication, be used to predict carcass nitrogen from measurements of carcass water in the remaining birds. Protein, fat, and water were expressed as proportions of body weight in the regression equations of Velu et al. (1972) and Cunningham and Morrison (1976). Farrell and Balnave (1977) reported a close relationship between the proportions of fat and water in hens. Work in this area has been extended from whole birds to eviserated carcasses (Pesti and Fletcher, 1983; Chambers and Fortin, 1984). There is interest in predicting body composition in terms of absolute quantities, proportions Contribution Numbers 1-737 Engineering and Statistical Research Centre and 1332 Animal Research Centre.
of body weight, and proportions of dry matter. Research examining the relationships that exist among the various body components was carried out to provide base data for developing prediction equations. This report presents the correlations found among the major chemical components in the entire bodies of growing broiler chicks. MATERIALS AND METHODS
Six data sets were obtained from comparative slaughter experiments with Shaver Starbro chicks. Some sets were subdivided on the basis of sex, age, or dietary treatment to increase homogeneity, consequently the strengths of the relationships described are more representative of those occurring in untreated broiler chick populations. The data sets and subsets are as follows. Set 1. 96 males, divided into 24 lots of four birds, 10 days of age, an initial slaughter group (Sibbald and Morse, 1984). Set 2. 25 males plus 29 females, 18 days of age, an initial slaughter group (Sibbald and Wolynetz, 1985). 2a. 25 males 2b. 29 females
2324
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ABSTRACT Prior to the development of equations to predict body composition, a study was made of the relationships among the major body components of growing broiler chicks. Nineteen data sets comprising information on the body compositions of 444 chicks were available. In addition to body weight variables studied included water, dry matter, protein, total neutral lipids, ash, and energy expressed in absolute amounts, as proportions of body weight, and as proportions of dry matter. There were strong, positive, linear relationships among all pairs of variables expressed as absolute amounts, indicating that an increase in one body component was accompanied by increases in the others. When data were expressed as proportions of body weight or of dry matter, the relationships were generally weaker and several were consistently negative. (Key words: water, protein, fat, body composition)
BODY COMPONENT RELATIONSHIPS
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Set 3. 40 males plus 80 females, 22 days of and Fortin, 1982). Chicks were weighed on reage, with varying energy intakes during the last moval from the freeze-dryer. Total water (TW) in the body was calculated by the equation TW four days (Sibbald and Wolynetz, 1985). = BW-TD. 3a. 40 males Total energy in the body (TE) was determined 3b. 80 females Set 4. 42 males, 10 days of age, an initial slaugh- by the following procedure. Carcass dry matter was equilibrated with atmospheric moisture and ter group (Sibbald and Wolynetz, 1986a). Set 5. 46 males plus 45 females, 10 to 16 days the air dry weight was measured. The air dry material was passed through a sieve and assayed of age (Sibbald and Wolynetz, 1986b). for gross energy using an adiabatic oxygen bomb 5a. 10 males, 10 days of age calorimiter. The TE was calculated by the equa5b. 12 males, 12 days of age tion TE = energy per unit weight X the air dry 5c. 10 males, 14 days of age weight. 5d. 14 males, 16 days of age Total protein in the body (TP) was determined 5e. 10 females, 10 days of age by the following procedure. The air dry carcass 5f. 10 females, 12 days of age was assayed for nitrogen by methods of the [As5g. 10 females, 14 days of age sociation of Official Analytical Chemists 5h. 15 females, 16 days of age Set 6. 113 males, 19 days of age, fed one of (AOAC), 1980]. The weight of the air dry carcass multiplied by the nitrogen per unit weight equals five lysine:TMEn diets (Sibbald and Wolynetz, total nitrogen (TN). Total protein in the body 1986a). 6a. 23 males, dietary lysine:TMEn ratio (g/ was calculated by the equation: TP = TN x 6.25. MJ2) = .59 Total neutral lipid in the body measured by 6b. 22 males, lysine:TMEn = .64 ether extraction of a sample of the air dry carcass 6c. 23 males, lysine:TMEn = .72 homogenate (AOAC, 1980). The weight of the 6d. 21 males, lysine:TMEn = .77 air dry carcass times the neutral lipid per unit 6e. 24 males, lysine:TMEn = .83 weight equals TL. The subsets created by separating birds of Total ash in the body (TA) was measured by different sexes or ages are easily understood. ashing a sample of the fat-extracted carcass Subsets 3a and 3b were not further subdivided (AOAC, 1980). The weight of the air dry carcass by diet because feeding was ad libitum and the times the ash per unit weight equals TA. number of birds for each sex by diet combination Total carcass residual (TR) is calculated by was small. Subsets 6a to 6e were obtained by the equation: TR = TD - TP - TL - TA. dividing the set into the five dietary lysine:TMEn treatments. Further subdivisions by basal dietxellulose ratio would have resulted in too RESULTS AND DISCUSSION small a subgroup size. There was no evidence Body composition data are summarized in that the arbitrary divisions into subgroups affected the nature of the relationships observed Table 1. There were large differences among the means of the data sets. However, the ranges among major body components. The data were examined using multiple linear within the sets were also large so that there was regression analysis. Pearson (rp) and Spearman overlapping among the sets. Thus, the high overrank (rs) correlation coefficients (Snedecor and all rp between some measurements were not due Cochran, 1967) were used to measure the body to there being six distinct and widely spaced clusters of observations. Data sets 1 and 4 did component relationships. Body weight (BW) was measured im- not lend themselves to subdivision; the ranges mediately after death, which was produced by for these two data sets were relatively small. administration of carbon dioxide. Total body dry The TR data are included to indicate the amount matter (TD), was determined by the following of the carcass composition unexplained by the procedure. After slaughter, each bird was laboratory analyses; they were excluded from weighed and frozen. Frozen chicks were auto- the statistical analyses. Subsequent analytical claved, homogenized, and freeze-dried (Sibbald work indicated that phospholipids are probably the major component of TR (Sibbald and Wolynetz, 1986b). 2 Expressing the data as a proportion of BW TME„ is true metabolizable energy corrected to zero or TD markedly reduced the relative variation nitrogen balance expressed as MJ (1 J = .239 cal).
1 2 3 4 5 6
1 2 3 4 5 6
1 2 3 4 5 6
3
2
1
24 54 120 42 91 113
158-211 289-563 361-609 156-200 159-432 144-512
.035 . 0 3 3 - . 0 3 7 .040 . 0 3 4 - . 0 4 3 .042 .038-.047 .036.033-.039 .037 . 0 3 4 - . 0 4 1 .039 . 0 3 4 - . 0 4 2
Total nitrogen/ total water
183 448 488 178 277 358
Body weight
(g)
2.59 2.10 2.11 2.21 2.08 2.36
.278 .324 .332 .312 .325 .299
2.44-2.75 1.67-2.57 1.84-2.56 2.01-2.37 1.80-2.54 1.88 2.90
TW d
.267-.291 .280-.374 .281-.352 .296-.332 .283-.357 .256-.347
TDb3
51 4 4 - 61 145 8 8 - 1 8 4 157 1 0 2 - 1 9 5 56 4 7 - 65 91 4 6 - 1 4 8 108 3 8 - 1 7 5
Total body dry matter
26.3 26.8 26.3 27.1 27.3 25.3
7.33 8.69 8.47 8.45 8.87 7.60
1.34 3.90 4.14 1.50 2.48 2.76 b
25.6-27.1 24.9-29.5 23.3-28.6 26.5-28.0 26.0-28.2 21.0-28.3
6 . 9 8 - 7.89 7.32-10.88 6 . 5 4 - 9.81 7 . 9 3 - 9.11 7 . 3 4 - 9.98 5 . 5 5 - 9.43 TEd
TE
1.14-1.77 2.31-4.96 2.36-5.40 1.26-1.76 1.21-4.09 .84-4.81
(MJ)
Total energy (TE) 2
b
(%)
.570 .528-.594 .530.443-.594 .558.483-.671 .496 . 4 5 9 - . 5 3 9 .484 . 4 4 0 - . 5 30 .576 . 4 6 9 - . 7 0 8
.151-.166 .154-.181 .164-.199 .143-.165 .146-.165 .151-.187 Tpd
TP
2 5 - 35 5 1 - 93 68-109 2 4 - 31 2 4 - 67 2 7 - 90
.159 .171 .179 .155 .157 .171
29 77 87 27 44 61
Total protein (TP)
The use of " b " and " d " as superscripts denotes proportions of body weight and total body dry matter, respectively.
10 18 22 10 10-16 19
(days)
Age
.320 .369 .338 .377 .391 .298
(%)
. . . . .
T
.0 .0 .0 .0 .0 .0
TL
13 2c IS 11 15 4-
.089 .120 .109 .118 .127 .091
16 54 54 21 36 34
Tot neut lipi (TL
TW D = 1 - T D D ; correlations of (X, TWD) and (X, T D b ) are of the same magnitude but opposite sign; X represents any other v
1 J = .239 cal.
Data set
No. of observations
TABLE 1. Summary of body composition: means and ranges of body components in tot and as a proportion of body weight and of total body dry matter.'
from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
BODY COMPONENT RELATIONSHIPS
much lower than the value of .85 reported by Velu et al. (1972). Conversely, the rp between TW1 and TPd was always positive and relatively strong. Similar results were evident for TWb with TAb when compared with TW1 and TAd. Many, but not all, of the relationships on a dry matter basis were stronger than those on a BW basis. On a per unit body weight or dry matter basis, some of the rp for subset c in Data set 5 seemed to be atypical compared with those for the other data sets (data not shown). There was no obvious explanation for this. The birds comprising Data set 5 were from a single hatch; after sexing, the males and females were reared in adjacent pens under identical conditions. The 10 bird of 5c were drawn at random from the 24 male birds alive at that time. The remaining 14 birds became 5d. On a per unit dry matter basis, some of the rp for Data set 1 were also atypical (data not shown). An objective of this study was to describe the nature and magnitude of the relationships among various body components. Such data serve to identify potentially fruitfull areas when attempting to develop prediction equations based upon body weight and water. The rp suggested that a satisfactory prediction of absolute composition should be possible. However, the rp also indicated that the prediction of proportions is less promising, perhaps because of the inverse relationship between the proportions of fat and water. Indeed, this relationship might be interpreted to suggest the use of fat plus water as a predictor, just as some early studies with other species considered fat-free empty body composition (see Mitchell, 1962). The fat:water relationship is well-known both in chickens (Mitchell et al., 1931) and in mammalian species (Spray and Widdowson, 1950) but as shown in Table 2, the variation in TW was not always satisfactorily explained by variation in TL. Many weaker but nevertheless significant (P<.05) trends were seen among the body component proportions making it apparent that variation in body composition, and therefore the prediction thereof, depends on the sum total of the changes in an array of variables. No attempt was made to test for equality of rp among subsets or for curvilinear relationships. Plots of the data (not shown) indicated that a low rp was due to an absence of any relationship between the variables and that a moderate rp corresponded to considerable scatter about a regression line; in particular, the plots did not in-
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(i.e., coefficient of variation) within data sets. Considering the extreme observations, it can be seen that in Data set 3, for example, TE ranged from 57 to 130% (i.e., 2.36 - 5.40 MJ) of the mean whereas comparable ranges from TE as a proportion of energy per unit of BW and TD, respectively, were 77 to 116% and 88 to 109%. The TN:TW ratio is included in Table 1. Although the range of absolute values was small (.033 to .047) relative to the mean of each data set, the observed range was substantial (11 to 23%). The rp between each pair of body components measured in absolute amounts is given in Table 2. All values are positive, indicating that an increase in one body component was accompanied by increases in the others. The rp of TW, TD, TE, and TP with BW were very high; those of TL and TA with BW were somewhat weaker. In most data sets, correlations between TD, TE, TP, TL and TA with BW were larger than with TW. A particularly strong relationship is that between TE and TD; the lowest value for rp was .98. The linear relationship between TE andTL was also strong. The rp among absolute amounts indicate that accurate predictions of total body composition may be possible from readily measured parameters such as BW, TW, and TD. This issue is examined in related papers (Wolynetz and Sibbald, 1986a,b). When the data were expressed as proportions of BW or TD, the relationships with BW and TD were noticeably weaker (Table 2). Similarly, the linear relationships among pairs of variables were generally weaker and more erratic. Exceptions included the relationships between the following pairs: TWb:TEb; TWb:TLb; TEb:TLb; TPd:TLd where the superscripts " b " and " d " denote proportions of BW and TD, respectively. The signs of the rp, which indicate the directions of the relationships, are perhaps more important than their magnitudes. For example, as BW increased, TWb, TPb, and TAb tended to decrease, whereas TLb and TEb increased. Together, these values indicated that heavier birds tended to be fatter both in absolute and proportional terms; however, the absolute amount of protein increased in heavier birds but the proportion of protein decreased. A comparison of the relationships between measurements expressed on a per unit body weight and on a per unit dry matter basis revealed many similarities, but there were some noteworthy differences. For example, the rp between TWb and TPb was weak and inconsistent and
2327
.97 .90 .99
.93 .83 .98
.59 .08 .91 -.29 .02
-.54 -.89 -.06 -.26 -.48
.04
.61 .21 .93 .11 .17
.15
-.60 -.94 -.24 .07 -.01
-.57 -.88 -.16 .35 .20
.22
TAd
-.36 -.64 .62 .39
.61
-.72 -.96 -.42 -.38 .64
-.54
TW d
-.72 -.94 -.46 -.38
-.54
.72 -.18 .96 -.25 .14
.10
TEd
.75 .43 .96 .04
.40
TEb .62
TPb
.02
Tpd
-.74 -.96 -.48 .00 -.11
TD
-.41 -.79 .56 .21
TD
.96 .80 .98
.99
TP
-.68 -.90 -.36 .35 .05
.11
.18
.76 .46 .96 .13 .27
TAd
-.35 -.62 .57 .43
.60
TA b
.91 .70 .98
.98
TA
TLd
.76 .41 .95 .23
.29
TLb
.73 .58 .94
.83
TL
b
-.82 -.94 -.36 -.15 -.52
-.74
TEd
-.97 -.99 -.86 -.68
-.96
TE
.99 .98 1.00
.99
XE
Pairs of variables 2
.94 .88 .99
.93
TL
.88 .46 .97 .53 .48
.74
TPd
.77 .39 .92 -.16 .54
.53
TAd
.21 -.16 .55 -.50
-.22
TAb
.88 .68 .96
.97
TA
-
-
T
-
-
. . .
.
T
Pooled within-subset correlation.
TW = Total water, TD = total body dry matter, TP = total protein, TL = total neutral lipid, TA = total ash, TE = total energy; b and d superscripts denot
-.90 -.97 -.43 -.25 -.56
-.82
TLd
TW d
-.94 -.98 -.62 -.49
-.90
.01 .28 -.61 .67 .08
TLb
TWb!
TD
TPb
.92 .84 .98
.97
TP
7
Minimum and maximum correlations for the 17 subsets omitting subsets 5c and 1.
Minimum and maximum correlations for the 18 subsets omitting subset 5c.
TD*> = 1 - TW D ; correlations of (X, TD^) and (X, TW^>) are of the same magnitude but opposite sign; X represens any other measurement.
6
!
Twbs
.91 .78 .98
.92 .80 .98
TA b
.94
.97
.98
.86 .68 .96
TE
TD
TA
TW
Critical values for 5% and 1% significance level, respectively, for both overall and pooled within-subset correlations are .10 and .12.
-.03
-.41
TLd
TEd
TW d
TPd
.59 .18 .91 .17
-.40 -.81 .48 .23
.56 .17 .90 -.06
-.52 -.87 -.06 -.26
BW
.15
.67
TWO'
.25
TLb
.83 .62 .96
.87
-.41
BW
.99
.97
TL
TPb
.96 .93 .99
.99 .96 1.00
TP
TE
TEb
.99
1.00
TD
"Minimum and maximum correlations for the 19 subsets.
3
3
1
Overall Withinsubset Pooled 2 Min.6 Max. 6 5c 1
Overall Withinsubset Pooled 3 Min.6 Max. 6 5c
Overall Withinsubset Pooled 3 Min.* Max. 4
TW
BW
TABLE 2. Overall, pooled within-sub set, and range of within-subset Pearson correlations1
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BODY COMPONENT RELATIONSHIPS
ACKNOWLEDGMENT
The authors thank S. Winter for her valuable technical assistance.
REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 11th ed. Assoc. Offic. Anal.
Chem., Washington, DC. Chambers, J. R., andA. Fortin, 1984. Live body and carcass measurements as predictors of chemical composition of carcasses of male broiler chickens. Poultry Sci. 63:2187-2196. Cunningham, D. C , and W. D. Morrison, 1976. Dietary energy and fat content as factors in the nutrition of developing egg strain pullets and young hens. 1. Effect of several parameters and body composition at sexual maturity. Poultry Sci. 55:85-97. Farrell, D. J., and D. Balnave, 1977. The in vivo estimation of body fat content in laying hens. Br. Poult. Sci. 18:381-384. Mitchell, H. H., 1962. Pages 193-195 in: Comparative Nutrition of Man and Domestic Animals. Vol. 1. Academic Press, New York, NY. Mitchell, H. H., L. E. Card, and T. S. Hamilton, 1931. A technical study of the growth of White Leghorn chickens. Univ. 111. Agric. Exp. St. Bull. 367. 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. Sibbald, I. R., and A. Fortin, 1982. Preparation of dry homogenates from whole and eviscerated chickens. Poultry Sci. 61:589-590. Sibbald, I. R., and P. M. Morse, 1984. Apreliminary investigation of the utilization of true metabolizable energy by chicks. Poultry Sci. 63:954-971. Sibbald, I. R., and M. S. Wolynetz, 1985. Short-term changes in broiler chick carcass composition associated with a range of intakes of a lipogenic diet. Poultry Sci. 64:2308-2313. Sibbald, I. R., and M. S. Wolynetz, 1986a. Effects of dietary lysine and feed intake on energy utilization and tissue synthesis by broiler chicks. Poultry Sci. 65:98-105. Sibbald, I. R., and M. S. Wolynetz, 1986b. Measurement of lipids in chicken carcass dry matter. Poultry Sci. 65:2299-2303. Sncdecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames, IA. Spray, C. M., and E. M. Widdowson, 1950. The effect of growth and development on the composition of mammals. Br. J. Nutr. 4:332-353. Summers, J. D., and H. Fisher, 1961. Net protein values for the growing chicken determined by carcass analysis: exploration of the method. J. Nutr. 75:435442. Velu, J. G., D. H. Baker, and H. M. Scott, 1972. Regression equations for determining body composition of young chicks. Poultry Sci. 51:698-699. Wolynetz, M. S., and I. R. Sibbald, 1986a. Prediction of major body components of broiler chicks. Poultry Sci. 65:2173-2185. Wolynetz, M. S., and I. R. Sibbald, 1986b. Prediction of major body components of broiler chicks from a small subset. Poultry Sci. 65:2167-2172.
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
dicate that low or moderate rp were indicative of a curvilinear relationship. For poultry breeders, the selection of birds (or of parents of birds) from a specific portion of the population distribution is important. In such situations, the relative postitions of birds within the population are of direct interest. Consequently the rs corresponding to the rp of Table 2 were calculated. The corresponding rs and rp were quite similar so that the former are not presented. The results obtained with these young chicks (10 to 22 days old) were similar to those obtained with market weight eviscerated carcasses by Chambers and Fortin (1984). Specifically, the pooled within-subset rp for TWb:TLb of -.94 was extremely similar to their reported fat:water correlation of-.96; their five correlations involving protein and ash on a dry matter basis differ by less than .05 from the corresponding pooled within-subset values shown in Table 2. These similarities suggest that the complex relationships observed in young birds may also exist in market weight birds. The lowest rp forTLb andTLd was .97, indicating very good agreement among the two methods of expressing the total neutral lipid proportion. In general, this agreement was reflected by a general similarity for an rp involving TLb and the corresponding value involving TLd. With regard to protein, the relationship between TPb and TPd was much weaker; rp ranged from .06 to .89. This report gives but a few examples to illustrate the complexity of the body component relationships and emphasize the importance of identifying correct selection parameters.
2329
1986 Poultry Science 65:2324-2329 INTRODUCTION
Measurement of the major chemical components of chicks (water, protein, fat, ash), as well as energy, is laborious and requires the use of equipment that may not be readily available. Prediction equations have been developed to simplify estimation of body composition, but the scope of such equations is generally limited. Summers and Fisher (1961) observed relatively constant watennitrogen ratios among the carcasses of chickens within experiments and proposed that the ratio, measured in chicks of one replication, be used to predict carcass nitrogen from measurements of carcass water in the remaining birds. Protein, fat, and water were expressed as proportions of body weight in the regression equations of Velu et al. (1972) and Cunningham and Morrison (1976). Farrell and Balnave (1977) reported a close relationship between the proportions of fat and water in hens. Work in this area has been extended from whole birds to eviserated carcasses (Pesti and Fletcher, 1983; Chambers and Fortin, 1984). There is interest in predicting body composition in terms of absolute quantities, proportions Contribution Numbers 1-737 Engineering and Statistical Research Centre and 1332 Animal Research Centre.
of body weight, and proportions of dry matter. Research examining the relationships that exist among the various body components was carried out to provide base data for developing prediction equations. This report presents the correlations found among the major chemical components in the entire bodies of growing broiler chicks. MATERIALS AND METHODS
Six data sets were obtained from comparative slaughter experiments with Shaver Starbro chicks. Some sets were subdivided on the basis of sex, age, or dietary treatment to increase homogeneity, consequently the strengths of the relationships described are more representative of those occurring in untreated broiler chick populations. The data sets and subsets are as follows. Set 1. 96 males, divided into 24 lots of four birds, 10 days of age, an initial slaughter group (Sibbald and Morse, 1984). Set 2. 25 males plus 29 females, 18 days of age, an initial slaughter group (Sibbald and Wolynetz, 1985). 2a. 25 males 2b. 29 females
2324
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
ABSTRACT Prior to the development of equations to predict body composition, a study was made of the relationships among the major body components of growing broiler chicks. Nineteen data sets comprising information on the body compositions of 444 chicks were available. In addition to body weight variables studied included water, dry matter, protein, total neutral lipids, ash, and energy expressed in absolute amounts, as proportions of body weight, and as proportions of dry matter. There were strong, positive, linear relationships among all pairs of variables expressed as absolute amounts, indicating that an increase in one body component was accompanied by increases in the others. When data were expressed as proportions of body weight or of dry matter, the relationships were generally weaker and several were consistently negative. (Key words: water, protein, fat, body composition)
BODY COMPONENT RELATIONSHIPS
2325
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
Set 3. 40 males plus 80 females, 22 days of and Fortin, 1982). Chicks were weighed on reage, with varying energy intakes during the last moval from the freeze-dryer. Total water (TW) in the body was calculated by the equation TW four days (Sibbald and Wolynetz, 1985). = BW-TD. 3a. 40 males Total energy in the body (TE) was determined 3b. 80 females Set 4. 42 males, 10 days of age, an initial slaugh- by the following procedure. Carcass dry matter was equilibrated with atmospheric moisture and ter group (Sibbald and Wolynetz, 1986a). Set 5. 46 males plus 45 females, 10 to 16 days the air dry weight was measured. The air dry material was passed through a sieve and assayed of age (Sibbald and Wolynetz, 1986b). for gross energy using an adiabatic oxygen bomb 5a. 10 males, 10 days of age calorimiter. The TE was calculated by the equa5b. 12 males, 12 days of age tion TE = energy per unit weight X the air dry 5c. 10 males, 14 days of age weight. 5d. 14 males, 16 days of age Total protein in the body (TP) was determined 5e. 10 females, 10 days of age by the following procedure. The air dry carcass 5f. 10 females, 12 days of age was assayed for nitrogen by methods of the [As5g. 10 females, 14 days of age sociation of Official Analytical Chemists 5h. 15 females, 16 days of age Set 6. 113 males, 19 days of age, fed one of (AOAC), 1980]. The weight of the air dry carcass multiplied by the nitrogen per unit weight equals five lysine:TMEn diets (Sibbald and Wolynetz, total nitrogen (TN). Total protein in the body 1986a). 6a. 23 males, dietary lysine:TMEn ratio (g/ was calculated by the equation: TP = TN x 6.25. MJ2) = .59 Total neutral lipid in the body measured by 6b. 22 males, lysine:TMEn = .64 ether extraction of a sample of the air dry carcass 6c. 23 males, lysine:TMEn = .72 homogenate (AOAC, 1980). The weight of the 6d. 21 males, lysine:TMEn = .77 air dry carcass times the neutral lipid per unit 6e. 24 males, lysine:TMEn = .83 weight equals TL. The subsets created by separating birds of Total ash in the body (TA) was measured by different sexes or ages are easily understood. ashing a sample of the fat-extracted carcass Subsets 3a and 3b were not further subdivided (AOAC, 1980). The weight of the air dry carcass by diet because feeding was ad libitum and the times the ash per unit weight equals TA. number of birds for each sex by diet combination Total carcass residual (TR) is calculated by was small. Subsets 6a to 6e were obtained by the equation: TR = TD - TP - TL - TA. dividing the set into the five dietary lysine:TMEn treatments. Further subdivisions by basal dietxellulose ratio would have resulted in too RESULTS AND DISCUSSION small a subgroup size. There was no evidence Body composition data are summarized in that the arbitrary divisions into subgroups affected the nature of the relationships observed Table 1. There were large differences among the means of the data sets. However, the ranges among major body components. The data were examined using multiple linear within the sets were also large so that there was regression analysis. Pearson (rp) and Spearman overlapping among the sets. Thus, the high overrank (rs) correlation coefficients (Snedecor and all rp between some measurements were not due Cochran, 1967) were used to measure the body to there being six distinct and widely spaced clusters of observations. Data sets 1 and 4 did component relationships. Body weight (BW) was measured im- not lend themselves to subdivision; the ranges mediately after death, which was produced by for these two data sets were relatively small. administration of carbon dioxide. Total body dry The TR data are included to indicate the amount matter (TD), was determined by the following of the carcass composition unexplained by the procedure. After slaughter, each bird was laboratory analyses; they were excluded from weighed and frozen. Frozen chicks were auto- the statistical analyses. Subsequent analytical claved, homogenized, and freeze-dried (Sibbald work indicated that phospholipids are probably the major component of TR (Sibbald and Wolynetz, 1986b). 2 Expressing the data as a proportion of BW TME„ is true metabolizable energy corrected to zero or TD markedly reduced the relative variation nitrogen balance expressed as MJ (1 J = .239 cal).
1 2 3 4 5 6
1 2 3 4 5 6
1 2 3 4 5 6
3
2
1
24 54 120 42 91 113
158-211 289-563 361-609 156-200 159-432 144-512
.035 . 0 3 3 - . 0 3 7 .040 . 0 3 4 - . 0 4 3 .042 .038-.047 .036.033-.039 .037 . 0 3 4 - . 0 4 1 .039 . 0 3 4 - . 0 4 2
Total nitrogen/ total water
183 448 488 178 277 358
Body weight
(g)
2.59 2.10 2.11 2.21 2.08 2.36
.278 .324 .332 .312 .325 .299
2.44-2.75 1.67-2.57 1.84-2.56 2.01-2.37 1.80-2.54 1.88 2.90
TW d
.267-.291 .280-.374 .281-.352 .296-.332 .283-.357 .256-.347
TDb3
51 4 4 - 61 145 8 8 - 1 8 4 157 1 0 2 - 1 9 5 56 4 7 - 65 91 4 6 - 1 4 8 108 3 8 - 1 7 5
Total body dry matter
26.3 26.8 26.3 27.1 27.3 25.3
7.33 8.69 8.47 8.45 8.87 7.60
1.34 3.90 4.14 1.50 2.48 2.76 b
25.6-27.1 24.9-29.5 23.3-28.6 26.5-28.0 26.0-28.2 21.0-28.3
6 . 9 8 - 7.89 7.32-10.88 6 . 5 4 - 9.81 7 . 9 3 - 9.11 7 . 3 4 - 9.98 5 . 5 5 - 9.43 TEd
TE
1.14-1.77 2.31-4.96 2.36-5.40 1.26-1.76 1.21-4.09 .84-4.81
(MJ)
Total energy (TE) 2
b
(%)
.570 .528-.594 .530.443-.594 .558.483-.671 .496 . 4 5 9 - . 5 3 9 .484 . 4 4 0 - . 5 30 .576 . 4 6 9 - . 7 0 8
.151-.166 .154-.181 .164-.199 .143-.165 .146-.165 .151-.187 Tpd
TP
2 5 - 35 5 1 - 93 68-109 2 4 - 31 2 4 - 67 2 7 - 90
.159 .171 .179 .155 .157 .171
29 77 87 27 44 61
Total protein (TP)
The use of " b " and " d " as superscripts denotes proportions of body weight and total body dry matter, respectively.
10 18 22 10 10-16 19
(days)
Age
.320 .369 .338 .377 .391 .298
(%)
. . . . .
T
.0 .0 .0 .0 .0 .0
TL
13 2c IS 11 15 4-
.089 .120 .109 .118 .127 .091
16 54 54 21 36 34
Tot neut lipi (TL
TW D = 1 - T D D ; correlations of (X, TWD) and (X, T D b ) are of the same magnitude but opposite sign; X represents any other v
1 J = .239 cal.
Data set
No. of observations
TABLE 1. Summary of body composition: means and ranges of body components in tot and as a proportion of body weight and of total body dry matter.'
from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
BODY COMPONENT RELATIONSHIPS
much lower than the value of .85 reported by Velu et al. (1972). Conversely, the rp between TW1 and TPd was always positive and relatively strong. Similar results were evident for TWb with TAb when compared with TW1 and TAd. Many, but not all, of the relationships on a dry matter basis were stronger than those on a BW basis. On a per unit body weight or dry matter basis, some of the rp for subset c in Data set 5 seemed to be atypical compared with those for the other data sets (data not shown). There was no obvious explanation for this. The birds comprising Data set 5 were from a single hatch; after sexing, the males and females were reared in adjacent pens under identical conditions. The 10 bird of 5c were drawn at random from the 24 male birds alive at that time. The remaining 14 birds became 5d. On a per unit dry matter basis, some of the rp for Data set 1 were also atypical (data not shown). An objective of this study was to describe the nature and magnitude of the relationships among various body components. Such data serve to identify potentially fruitfull areas when attempting to develop prediction equations based upon body weight and water. The rp suggested that a satisfactory prediction of absolute composition should be possible. However, the rp also indicated that the prediction of proportions is less promising, perhaps because of the inverse relationship between the proportions of fat and water. Indeed, this relationship might be interpreted to suggest the use of fat plus water as a predictor, just as some early studies with other species considered fat-free empty body composition (see Mitchell, 1962). The fat:water relationship is well-known both in chickens (Mitchell et al., 1931) and in mammalian species (Spray and Widdowson, 1950) but as shown in Table 2, the variation in TW was not always satisfactorily explained by variation in TL. Many weaker but nevertheless significant (P<.05) trends were seen among the body component proportions making it apparent that variation in body composition, and therefore the prediction thereof, depends on the sum total of the changes in an array of variables. No attempt was made to test for equality of rp among subsets or for curvilinear relationships. Plots of the data (not shown) indicated that a low rp was due to an absence of any relationship between the variables and that a moderate rp corresponded to considerable scatter about a regression line; in particular, the plots did not in-
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
(i.e., coefficient of variation) within data sets. Considering the extreme observations, it can be seen that in Data set 3, for example, TE ranged from 57 to 130% (i.e., 2.36 - 5.40 MJ) of the mean whereas comparable ranges from TE as a proportion of energy per unit of BW and TD, respectively, were 77 to 116% and 88 to 109%. The TN:TW ratio is included in Table 1. Although the range of absolute values was small (.033 to .047) relative to the mean of each data set, the observed range was substantial (11 to 23%). The rp between each pair of body components measured in absolute amounts is given in Table 2. All values are positive, indicating that an increase in one body component was accompanied by increases in the others. The rp of TW, TD, TE, and TP with BW were very high; those of TL and TA with BW were somewhat weaker. In most data sets, correlations between TD, TE, TP, TL and TA with BW were larger than with TW. A particularly strong relationship is that between TE and TD; the lowest value for rp was .98. The linear relationship between TE andTL was also strong. The rp among absolute amounts indicate that accurate predictions of total body composition may be possible from readily measured parameters such as BW, TW, and TD. This issue is examined in related papers (Wolynetz and Sibbald, 1986a,b). When the data were expressed as proportions of BW or TD, the relationships with BW and TD were noticeably weaker (Table 2). Similarly, the linear relationships among pairs of variables were generally weaker and more erratic. Exceptions included the relationships between the following pairs: TWb:TEb; TWb:TLb; TEb:TLb; TPd:TLd where the superscripts " b " and " d " denote proportions of BW and TD, respectively. The signs of the rp, which indicate the directions of the relationships, are perhaps more important than their magnitudes. For example, as BW increased, TWb, TPb, and TAb tended to decrease, whereas TLb and TEb increased. Together, these values indicated that heavier birds tended to be fatter both in absolute and proportional terms; however, the absolute amount of protein increased in heavier birds but the proportion of protein decreased. A comparison of the relationships between measurements expressed on a per unit body weight and on a per unit dry matter basis revealed many similarities, but there were some noteworthy differences. For example, the rp between TWb and TPb was weak and inconsistent and
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.97 .90 .99
.93 .83 .98
.59 .08 .91 -.29 .02
-.54 -.89 -.06 -.26 -.48
.04
.61 .21 .93 .11 .17
.15
-.60 -.94 -.24 .07 -.01
-.57 -.88 -.16 .35 .20
.22
TAd
-.36 -.64 .62 .39
.61
-.72 -.96 -.42 -.38 .64
-.54
TW d
-.72 -.94 -.46 -.38
-.54
.72 -.18 .96 -.25 .14
.10
TEd
.75 .43 .96 .04
.40
TEb .62
TPb
.02
Tpd
-.74 -.96 -.48 .00 -.11
TD
-.41 -.79 .56 .21
TD
.96 .80 .98
.99
TP
-.68 -.90 -.36 .35 .05
.11
.18
.76 .46 .96 .13 .27
TAd
-.35 -.62 .57 .43
.60
TA b
.91 .70 .98
.98
TA
TLd
.76 .41 .95 .23
.29
TLb
.73 .58 .94
.83
TL
b
-.82 -.94 -.36 -.15 -.52
-.74
TEd
-.97 -.99 -.86 -.68
-.96
TE
.99 .98 1.00
.99
XE
Pairs of variables 2
.94 .88 .99
.93
TL
.88 .46 .97 .53 .48
.74
TPd
.77 .39 .92 -.16 .54
.53
TAd
.21 -.16 .55 -.50
-.22
TAb
.88 .68 .96
.97
TA
-
-
T
-
-
. . .
.
T
Pooled within-subset correlation.
TW = Total water, TD = total body dry matter, TP = total protein, TL = total neutral lipid, TA = total ash, TE = total energy; b and d superscripts denot
-.90 -.97 -.43 -.25 -.56
-.82
TLd
TW d
-.94 -.98 -.62 -.49
-.90
.01 .28 -.61 .67 .08
TLb
TWb!
TD
TPb
.92 .84 .98
.97
TP
7
Minimum and maximum correlations for the 17 subsets omitting subsets 5c and 1.
Minimum and maximum correlations for the 18 subsets omitting subset 5c.
TD*> = 1 - TW D ; correlations of (X, TD^) and (X, TW^>) are of the same magnitude but opposite sign; X represens any other measurement.
6
!
Twbs
.91 .78 .98
.92 .80 .98
TA b
.94
.97
.98
.86 .68 .96
TE
TD
TA
TW
Critical values for 5% and 1% significance level, respectively, for both overall and pooled within-subset correlations are .10 and .12.
-.03
-.41
TLd
TEd
TW d
TPd
.59 .18 .91 .17
-.40 -.81 .48 .23
.56 .17 .90 -.06
-.52 -.87 -.06 -.26
BW
.15
.67
TWO'
.25
TLb
.83 .62 .96
.87
-.41
BW
.99
.97
TL
TPb
.96 .93 .99
.99 .96 1.00
TP
TE
TEb
.99
1.00
TD
"Minimum and maximum correlations for the 19 subsets.
3
3
1
Overall Withinsubset Pooled 2 Min.6 Max. 6 5c 1
Overall Withinsubset Pooled 3 Min.6 Max. 6 5c
Overall Withinsubset Pooled 3 Min.* Max. 4
TW
BW
TABLE 2. Overall, pooled within-sub set, and range of within-subset Pearson correlations1
ed from http://ps.oxfordjournals.org/ at Northern Arizona University on June 3, 2015
BODY COMPONENT RELATIONSHIPS
ACKNOWLEDGMENT
The authors thank S. Winter for her valuable technical assistance.
REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 11th ed. Assoc. Offic. Anal.
Chem., Washington, DC. Chambers, J. R., andA. Fortin, 1984. Live body and carcass measurements as predictors of chemical composition of carcasses of male broiler chickens. Poultry Sci. 63:2187-2196. Cunningham, D. C , and W. D. Morrison, 1976. Dietary energy and fat content as factors in the nutrition of developing egg strain pullets and young hens. 1. Effect of several parameters and body composition at sexual maturity. Poultry Sci. 55:85-97. Farrell, D. J., and D. Balnave, 1977. The in vivo estimation of body fat content in laying hens. Br. Poult. Sci. 18:381-384. Mitchell, H. H., 1962. Pages 193-195 in: Comparative Nutrition of Man and Domestic Animals. Vol. 1. Academic Press, New York, NY. Mitchell, H. H., L. E. Card, and T. S. Hamilton, 1931. A technical study of the growth of White Leghorn chickens. Univ. 111. Agric. Exp. St. Bull. 367. 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. Sibbald, I. R., and A. Fortin, 1982. Preparation of dry homogenates from whole and eviscerated chickens. Poultry Sci. 61:589-590. Sibbald, I. R., and P. M. Morse, 1984. Apreliminary investigation of the utilization of true metabolizable energy by chicks. Poultry Sci. 63:954-971. Sibbald, I. R., and M. S. Wolynetz, 1985. Short-term changes in broiler chick carcass composition associated with a range of intakes of a lipogenic diet. Poultry Sci. 64:2308-2313. Sibbald, I. R., and M. S. Wolynetz, 1986a. Effects of dietary lysine and feed intake on energy utilization and tissue synthesis by broiler chicks. Poultry Sci. 65:98-105. Sibbald, I. R., and M. S. Wolynetz, 1986b. Measurement of lipids in chicken carcass dry matter. Poultry Sci. 65:2299-2303. Sncdecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames, IA. Spray, C. M., and E. M. Widdowson, 1950. The effect of growth and development on the composition of mammals. Br. J. Nutr. 4:332-353. Summers, J. D., and H. Fisher, 1961. Net protein values for the growing chicken determined by carcass analysis: exploration of the method. J. Nutr. 75:435442. Velu, J. G., D. H. Baker, and H. M. Scott, 1972. Regression equations for determining body composition of young chicks. Poultry Sci. 51:698-699. Wolynetz, M. S., and I. R. Sibbald, 1986a. Prediction of major body components of broiler chicks. Poultry Sci. 65:2173-2185. Wolynetz, M. S., and I. R. Sibbald, 1986b. Prediction of major body components of broiler chicks from a small subset. Poultry Sci. 65:2167-2172.
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dicate that low or moderate rp were indicative of a curvilinear relationship. For poultry breeders, the selection of birds (or of parents of birds) from a specific portion of the population distribution is important. In such situations, the relative postitions of birds within the population are of direct interest. Consequently the rs corresponding to the rp of Table 2 were calculated. The corresponding rs and rp were quite similar so that the former are not presented. The results obtained with these young chicks (10 to 22 days old) were similar to those obtained with market weight eviscerated carcasses by Chambers and Fortin (1984). Specifically, the pooled within-subset rp for TWb:TLb of -.94 was extremely similar to their reported fat:water correlation of-.96; their five correlations involving protein and ash on a dry matter basis differ by less than .05 from the corresponding pooled within-subset values shown in Table 2. These similarities suggest that the complex relationships observed in young birds may also exist in market weight birds. The lowest rp forTLb andTLd was .97, indicating very good agreement among the two methods of expressing the total neutral lipid proportion. In general, this agreement was reflected by a general similarity for an rp involving TLb and the corresponding value involving TLd. With regard to protein, the relationship between TPb and TPd was much weaker; rp ranged from .06 to .89. This report gives but a few examples to illustrate the complexity of the body component relationships and emphasize the importance of identifying correct selection parameters.
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