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The Appraisal of Conformation in Broilers1
The Appraisal of Conformation in Broilers1 W. L. BLOW AND E. W. GLAZENER North Carolina Agricultural Experiment Station, Raleigh (Received for publication November 9, 1951)
T N RECENT years increased interest -*• in the improvement of conformation in broilers has been initiated by consumer preferences for chickens with superior fleshing qualities. This interest has been fostered to a large extent by the rapid expansion of the broiler industry and the stimulating effects of the "Chicken-ofTomorrow" contest, which was designed to improve the meat quality of poultry. Major emphasis in this improvement of broilers has been placed on increased weight at marketing age, or earlier marketing at broiler weight, with improved conformation. At the present time general impressions of conformation and meat quality in broilers have become more or less synonymous with fleshing or development of the breast area. This improvement of conformation has been sought through various measurements which have been used to appraise the desirability of the dressed carcass from the phenotype of the live bird. Since very little is known about the relative effectiveness of these attempts to evaluate confor nation objectively, the following investigation was undertaken to secure some information on the relative value of various measurements for appraising conformation in broilers as reflected by breast fleshing. Body measurements which are used to evaluate conformation in broilers can 1
Contribution from the Department of Poultry Science, North Carolina Agricultural Experiment Station as Journal Paper 403.
only assume a degree of utility after it has been shown that this character can be improved by selection. That the body shape of the sire is transmitted to his progeny was observed by Maw and Maw (1938) and confirmed by Jaap and Thompson (1940). Lerner, Asmundson and Cruden (1947) indicated that breast width was amenable to selection when they obtained a heritability estimate of approximately .20 for breast width in a randomly selected sample of New Hampshire broilers. Various workers have attempted to determine methods of measuring living birds which would describe the quality of the dressed carcass. Jaap and Penquite (1938), in evaluating several criteria of conformation in turkeys and roosters, found that the relation between body weight and breast width measured by the wire solder method was a sensitive criterion of market quality. This method, however, was accepted by these workers as being a less reliable index than the ratio of shank length to the cube root of body weight. This cube root ratio has proved unsatisfactory for evaluating conformation in the work of Scott (1940), Doleck, Wilson and Poley (1941), and Frischknecht and Jull (1946). Gutteridge and O'Neil (1942) assumed that the angle of the breast was the most important of the individual body measurements for appraising market grade. Frischknecht and Jull (1946) rated various body measurements as criteria for measuring the body conformation of
654
CONFORMATION IN BROILERS
broilers as reflected by market grade. In this study the cross-sectional breast area proved to be the best index of market grade; however, live weight of the birds had the highest degree of relationship with the amount of breast fleshing. Breast width was measured relative to body depth by Bird (1948) through the use of a scale which made both measurements simultaneously. Selection in this case was based on the size of the deviation of actual breast width from the width expected to conform to a specified depth of body. MATERIALS AND METHODS
One hundred cockerels, approximately eleven weeks of age, from a broiler strain of New Hampshires were used in this study. Feed was withdrawn from the birds on the afternoon before the measurements were made on the live birds. The following day the birds were weighed to the nearest half-ounce, and a handling score based on the observed breast fleshing was assigned to each bird. Handling score was divided into three grades (1, 2, and 3) with the smallest numeral assigned to the birds with apparent superior fleshing qualities. Only one weight or measurement was made on each bird at a particular handling in order to eliminate any prejudice in subsequent measurements. The following breast measurements were made on each bird: 1. Width of the breast with vernier calipers at a point approximately f of an inch posterior to the tip of the keel and 1 | inches above the keel. 2. Impressions of the contour of the breast from the same point on the keel, using wire solder which was firmly molded over the breast. These impressions were transferred to ruled paper, and later the area included in this cross-sectional area to a depth of 1 | inches above the keel was computed.
655
3. The angle of slope of the breast from the same point on the keel using an instrument which was developed for this study. 4. The series of measurements using the Bird scale which measures \ the breast width at a point above the keel equivalent to \ of the body depth. The regression of breast width on body depth was computed from the above measurements which were collected in this study. Deviations of the observed breast widths from this regression line were the phenotypic values which were assigned to the birds for the analysis of data. A positive deviation was indicative of a breast width greater than that expected to conform to a specified body depth. After the live measurements were completed, the birds were killed, dressed, and eviscerated. The same series of measurements and observations were then repeated on these birds; after which, the pectoral muscles were removed from the sternum, and the total breast meat of each bird weighed to the nearest gram. RESULTS AND DISCUSSION
It is generally assumed that roundness of breast or superior conformation is associated with the meat yield of poultry; although, Maw and Maw (1939) observed that the correlations between edible flesh and various body measurements not including breast measurements were very low. Frischknecht and Jull (1946), however, found that there were reasonably high correlations between various breast measurements and the amount of breast meat. Since the production of meat is the ultimate aim in broiler production, the criteria for measuring breast development were evaluated on the basis of their degree of association with the amount of breast meat on the birds in this study. This objective manner of appraising the
656
W. L. BLOW AND E. W. GLAZENER
TABLE 1.—Mean weight and measurements of
scale appears to offer an extremely limited opportunity to appraise carcass conforMeasurement Live Eviscerated mation through the live index. Weight in oz. 49.66±.57 38.88± .46* A comparison of the total correlations Breast width in cm. 3.94±.04 4.06± .05 Angle in degrees 58.13±.49 57.43± .48 between the various live measurements Cross-section area in sq. cm. 10.91±.ll 10.57± .10 Bird scale and the yield of breast meat illustrates Depth in cm. 10.49±.06 9.79± .05 i breast width in cm. 2.32±.04 2.06± .04 that the weight of the birds was the most Weight of breast meat in gms. — 144.95±2.48 efficient of these measurements for esti* Includes gizzard, liver, and heart. mating the amount of breast fleshing. Of different measurements was not due to an the breast measurements the cross-secunderestimate of the importance of con- tional area of the breast had the highest tour, but to the seemingly greater im- correlation with the amount of breast portance of meat yield, whatever its rela- meat, while the breast width and angle tion to conformation may be. This is proved much more efficient criteria than especially true in view of present market- the Bird index. Thus these data show that ing methods when an increasing percent- changes in body weight and breast measage of young birds for frying is being sold urements are generally attended by concomitant changes in the amount of breast as "cut-up" chicken. fleshing, and that body weight is the The mean weights and measurements superior single measurement for estimatwith their standard errors are presented ing the quantity of meat on the breast. in Table 1. Correlations between these Correlations involving the Bird index live and eviscerated measurements (see are not strictly comparable with those Table 2) indicate that with the exception involving other measurements, since a of body weight, the live measurements prior effort has been made to remove the have a relatively limited predictive value for estimating the corresponding measure- influence of body size from the index by ment on the eviscerated birds. Little discounting the postive effect of body difference is observed here between breast depth. Therefore, the correlation between width, cross-sectional area, and breast the Bird index and the yield of breast angle where at best only 61 percent of the meat is in effect a partial correlation since variance in live measurements is dupli- the breast widths have been adjusted for cated in that of the eviscerated birds. A differences in body depth. That this incorrelation value of .2942 between the fluence has not been entirely removed is paired indexes derived from the Bird apparent from the positive correlation between the Bird index and live weight. T A B L E 2.—Total and multiple correlations involving If the heritability of a character is body weight, breast measurements, and weight of breast meat of live and eviscerated birds low, the importance of a precise measure of the character is magnified. While there Live Eviscerweight is no information available on the magLive Weight Live ated and body of breast weight of measurement measurenitude of the heritability of breast fleshing, weight meat ment breast meat* there is no reason to believe that it is .9361 Body weight .8077 — exceptionally high. In the case of breast Breast width .7322 .4541 .5951 .8473 .7642 .5944 Breast angle .5781 .8168 fleshing only 65 percent of the variance is Cross-section . 7795 .5887 breast area .7224 .8636 explained by the regression on body Bird index .2942. .3120 .3153 .8104 weight which is the most efficient single * Multiple correlations between weight of breast meat and criterion of this character. I t seems that body weight and breast measurement. live and eviscerated birds
CONFORMATION IN BROILERS
an appraisal of the criteria then would hinge on the additional information on breast fleshing secured from using the breast measurements singly in combination with body weight as a basis for selection. The multiple correlations presented in Table 2 indicate that an additional 11 percent of the variance of breast meat is attributable to the independent contribution of cross-sectional area, while practically no additional information is gathered by using the Bird index or the breast angle. Although Lerner, Asmundson and Cruden (1947) observed a low positive relationship between body weight and breast measurement, the data in the present study show that the correlation between these two characters may be much higher. If the latter is true, the value of breast measurements for appraising breast fleshing would be diminished because of this association. The relationships presented here illustrate that the breast angle would be a more efficient criterion than breast width on the basis of the total correlations; however, the addition of body weight as a third variable actually would made breast width a more valuable measurement. A comparison of the relative weights that would be placed on body weight and breast measurement in selecting for breast fleshing is readily apparent from the standard partial regressions involving these characters. These regressions are: body weight and crosssectional area body weight and breast width body weight and breast angle body weight and Bird index
m'= .5851 a>'-f-.3779 V m'= .6769 w'+.3159
V
w ' = . 7 1 7 5 w'+. 1514 V m' = . 7856 w'+. 0701 b'
where m' is the weight of the breast in standard deviates, and w' and b' are the body weight and breast measurement respectively in standard deviates. The
657
constant associated with w' is the standard regression of breast meat on body weight independent of breast measurement, while the constant associated with breast measurement is the standard regression of breast meat on breast measurement independent of body weight. Thus in terms of standard measurement approximately 11 times as much weight would be placed on body weight as on the Bird index where both measurements are used in a selection program to improve breast fleshing. Only 1.5 times as much weight would be placed on body weight as on cross-sectional area where both of these measurements are used. A test of significance of the standard regressions of breast fleshing on breast measurement independent of body weight is a test of whether or not the multiple correlations are significantly different from the correlation between breast fleshing and body weight. The tests of significance by means of /.indicate that in no case are these standard regressions significant at the 5 percent level; although, the standard regressions involving the cross-sectional area and breast width are approaching significance at this level. The relatively limited gain in efficiency obtained by using a breast measurement in addition to body weight as a basis for appraising breast fleshing would seem to preclude the necessity for extensive or time-consuming breast measurements. Examination through handling is desirable from the standpoint of eliminating birds with crooked keels and other visible defects. If at the same time a quality score assigned on the basis of the apparent degree of breast fleshing were a reliable independent index of this fleshing, any need for further breast measurements might be eliminated. Although the correlation ratio between live handling score and weight of breast meat is .6833, the
658
W. L. BLOW AND E. W. GLAZENER
cockerels in grades 1, 2, and 3 weighed 54.7, 48.7, and 39.8 ounces respectively. This distribution indicates that handling quality is influenced in general to a considerable extent by live weight, and that the gain expected from additional information based on a handling score is inconsequential. The performance of this variable in multiple regression with live weight suggests that only an additional two percent of the variance in breast fleshing is accounted for by including handling score in the predictive equation. On the basis of these data the crosssectional breast area and breast width were the most desirable breast measurement when used in conjunction with body weight; however, the latter method has very distinct advantages because of its simplicity and rapidity in use. For these reasons breast width measured with calipers at a suitable distance above the keel appears to be the superior breast measurement for estimating breast fleshing in broilers. An appraisal of the different criteria naturally leads to the question of whether or not a breast measurement in addition to body weight is a worthwhile effort. This question can best be answered by pointing out the limited gain in precision effected by making the additional measurement. Broiler producers are still paid primarily for weight; and present grades, which supposedly reflect differences in fleshing, are largely determined by differrences in body weight. These factors are important considerations in determining whether or not a breeder is justified in expending considerable effort to improve the amount of breast fleshing. SUMMARY
Several criteria of conformation were used with 100 broiler New Hampshires to appraise the yield of breast meat in broilers. These criteria included breast width,
breast angle, cross-sectional breast area, the Bird index, handling quality, and body weight. Body weight appeared to be the superior single observation for evaluating the amount of breast fleshing. When the breast measurements were used singly in combination with body weight as a basis for selection, breast width and the crosssectional breast area had the highest relationship with the yield of breast meat. Breast width, because of the ease of measuring, was recommended for use in conjunction with body weight for selecting individuals with superior fleshing qualities. REFERENCES Bird, S., 1948. Quantitative determination and segregation of breast conformation in poultry. Poultry Sci. 27: 506-508. Doleck, R. L., W. O. Wilson and W. E. Poley, 1941. Physical measurements of carcass quality in roosters. Poultry Sci. 20: 161-170. Frischknecht, C. O., and M. A. Jull, 1946. Amount of breast meat and live and dressed grades in relation to body measurements in 12-week old purebred and crossbred chickens. Poultry Sci. 25:330-345. Gutteridge, H. S., and J. B. O'Neil, 1942. The relative effect of environment and heredity upon body measurements and production characteristics in poultry. I. Period of growth. Sci. Agr. 22: 378-389. Jaap, R. G., and R. Penquite, 1938. Criteria of conformation in market poultry. Poultry Sci. 17: 425-430. Jaap, R. G., and R. B. Thompson, 1940. Heritable differences in conformation of adult fowl. Poultry Sci. 19: 73-78. Lerner, I. M., V. S. Asmundson and D. M. Cruden, 1947. Poultry Sci. 26: 515-524. Maw, W. A., and A. J. G. Maw, 1938. The influence of type of sire on the body size of the progeny. U. S. Egg and Poultry Mag. 44: 78-84. Maw, W. A., and A. J. G. Maw, 1939. The relation of body measurements to the fattening grains and the percentage of edible flesh in the fowl. Sci. Agr. 19: 589-596. Scott, H. M., 1940. Checking market grades with meat measurements. U. S. Egg and Poultry Mag. 46:717-719.
T N RECENT years increased interest -*• in the improvement of conformation in broilers has been initiated by consumer preferences for chickens with superior fleshing qualities. This interest has been fostered to a large extent by the rapid expansion of the broiler industry and the stimulating effects of the "Chicken-ofTomorrow" contest, which was designed to improve the meat quality of poultry. Major emphasis in this improvement of broilers has been placed on increased weight at marketing age, or earlier marketing at broiler weight, with improved conformation. At the present time general impressions of conformation and meat quality in broilers have become more or less synonymous with fleshing or development of the breast area. This improvement of conformation has been sought through various measurements which have been used to appraise the desirability of the dressed carcass from the phenotype of the live bird. Since very little is known about the relative effectiveness of these attempts to evaluate confor nation objectively, the following investigation was undertaken to secure some information on the relative value of various measurements for appraising conformation in broilers as reflected by breast fleshing. Body measurements which are used to evaluate conformation in broilers can 1
Contribution from the Department of Poultry Science, North Carolina Agricultural Experiment Station as Journal Paper 403.
only assume a degree of utility after it has been shown that this character can be improved by selection. That the body shape of the sire is transmitted to his progeny was observed by Maw and Maw (1938) and confirmed by Jaap and Thompson (1940). Lerner, Asmundson and Cruden (1947) indicated that breast width was amenable to selection when they obtained a heritability estimate of approximately .20 for breast width in a randomly selected sample of New Hampshire broilers. Various workers have attempted to determine methods of measuring living birds which would describe the quality of the dressed carcass. Jaap and Penquite (1938), in evaluating several criteria of conformation in turkeys and roosters, found that the relation between body weight and breast width measured by the wire solder method was a sensitive criterion of market quality. This method, however, was accepted by these workers as being a less reliable index than the ratio of shank length to the cube root of body weight. This cube root ratio has proved unsatisfactory for evaluating conformation in the work of Scott (1940), Doleck, Wilson and Poley (1941), and Frischknecht and Jull (1946). Gutteridge and O'Neil (1942) assumed that the angle of the breast was the most important of the individual body measurements for appraising market grade. Frischknecht and Jull (1946) rated various body measurements as criteria for measuring the body conformation of
654
CONFORMATION IN BROILERS
broilers as reflected by market grade. In this study the cross-sectional breast area proved to be the best index of market grade; however, live weight of the birds had the highest degree of relationship with the amount of breast fleshing. Breast width was measured relative to body depth by Bird (1948) through the use of a scale which made both measurements simultaneously. Selection in this case was based on the size of the deviation of actual breast width from the width expected to conform to a specified depth of body. MATERIALS AND METHODS
One hundred cockerels, approximately eleven weeks of age, from a broiler strain of New Hampshires were used in this study. Feed was withdrawn from the birds on the afternoon before the measurements were made on the live birds. The following day the birds were weighed to the nearest half-ounce, and a handling score based on the observed breast fleshing was assigned to each bird. Handling score was divided into three grades (1, 2, and 3) with the smallest numeral assigned to the birds with apparent superior fleshing qualities. Only one weight or measurement was made on each bird at a particular handling in order to eliminate any prejudice in subsequent measurements. The following breast measurements were made on each bird: 1. Width of the breast with vernier calipers at a point approximately f of an inch posterior to the tip of the keel and 1 | inches above the keel. 2. Impressions of the contour of the breast from the same point on the keel, using wire solder which was firmly molded over the breast. These impressions were transferred to ruled paper, and later the area included in this cross-sectional area to a depth of 1 | inches above the keel was computed.
655
3. The angle of slope of the breast from the same point on the keel using an instrument which was developed for this study. 4. The series of measurements using the Bird scale which measures \ the breast width at a point above the keel equivalent to \ of the body depth. The regression of breast width on body depth was computed from the above measurements which were collected in this study. Deviations of the observed breast widths from this regression line were the phenotypic values which were assigned to the birds for the analysis of data. A positive deviation was indicative of a breast width greater than that expected to conform to a specified body depth. After the live measurements were completed, the birds were killed, dressed, and eviscerated. The same series of measurements and observations were then repeated on these birds; after which, the pectoral muscles were removed from the sternum, and the total breast meat of each bird weighed to the nearest gram. RESULTS AND DISCUSSION
It is generally assumed that roundness of breast or superior conformation is associated with the meat yield of poultry; although, Maw and Maw (1939) observed that the correlations between edible flesh and various body measurements not including breast measurements were very low. Frischknecht and Jull (1946), however, found that there were reasonably high correlations between various breast measurements and the amount of breast meat. Since the production of meat is the ultimate aim in broiler production, the criteria for measuring breast development were evaluated on the basis of their degree of association with the amount of breast meat on the birds in this study. This objective manner of appraising the
656
W. L. BLOW AND E. W. GLAZENER
TABLE 1.—Mean weight and measurements of
scale appears to offer an extremely limited opportunity to appraise carcass conforMeasurement Live Eviscerated mation through the live index. Weight in oz. 49.66±.57 38.88± .46* A comparison of the total correlations Breast width in cm. 3.94±.04 4.06± .05 Angle in degrees 58.13±.49 57.43± .48 between the various live measurements Cross-section area in sq. cm. 10.91±.ll 10.57± .10 Bird scale and the yield of breast meat illustrates Depth in cm. 10.49±.06 9.79± .05 i breast width in cm. 2.32±.04 2.06± .04 that the weight of the birds was the most Weight of breast meat in gms. — 144.95±2.48 efficient of these measurements for esti* Includes gizzard, liver, and heart. mating the amount of breast fleshing. Of different measurements was not due to an the breast measurements the cross-secunderestimate of the importance of con- tional area of the breast had the highest tour, but to the seemingly greater im- correlation with the amount of breast portance of meat yield, whatever its rela- meat, while the breast width and angle tion to conformation may be. This is proved much more efficient criteria than especially true in view of present market- the Bird index. Thus these data show that ing methods when an increasing percent- changes in body weight and breast measage of young birds for frying is being sold urements are generally attended by concomitant changes in the amount of breast as "cut-up" chicken. fleshing, and that body weight is the The mean weights and measurements superior single measurement for estimatwith their standard errors are presented ing the quantity of meat on the breast. in Table 1. Correlations between these Correlations involving the Bird index live and eviscerated measurements (see are not strictly comparable with those Table 2) indicate that with the exception involving other measurements, since a of body weight, the live measurements prior effort has been made to remove the have a relatively limited predictive value for estimating the corresponding measure- influence of body size from the index by ment on the eviscerated birds. Little discounting the postive effect of body difference is observed here between breast depth. Therefore, the correlation between width, cross-sectional area, and breast the Bird index and the yield of breast angle where at best only 61 percent of the meat is in effect a partial correlation since variance in live measurements is dupli- the breast widths have been adjusted for cated in that of the eviscerated birds. A differences in body depth. That this incorrelation value of .2942 between the fluence has not been entirely removed is paired indexes derived from the Bird apparent from the positive correlation between the Bird index and live weight. T A B L E 2.—Total and multiple correlations involving If the heritability of a character is body weight, breast measurements, and weight of breast meat of live and eviscerated birds low, the importance of a precise measure of the character is magnified. While there Live Eviscerweight is no information available on the magLive Weight Live ated and body of breast weight of measurement measurenitude of the heritability of breast fleshing, weight meat ment breast meat* there is no reason to believe that it is .9361 Body weight .8077 — exceptionally high. In the case of breast Breast width .7322 .4541 .5951 .8473 .7642 .5944 Breast angle .5781 .8168 fleshing only 65 percent of the variance is Cross-section . 7795 .5887 breast area .7224 .8636 explained by the regression on body Bird index .2942. .3120 .3153 .8104 weight which is the most efficient single * Multiple correlations between weight of breast meat and criterion of this character. I t seems that body weight and breast measurement. live and eviscerated birds
CONFORMATION IN BROILERS
an appraisal of the criteria then would hinge on the additional information on breast fleshing secured from using the breast measurements singly in combination with body weight as a basis for selection. The multiple correlations presented in Table 2 indicate that an additional 11 percent of the variance of breast meat is attributable to the independent contribution of cross-sectional area, while practically no additional information is gathered by using the Bird index or the breast angle. Although Lerner, Asmundson and Cruden (1947) observed a low positive relationship between body weight and breast measurement, the data in the present study show that the correlation between these two characters may be much higher. If the latter is true, the value of breast measurements for appraising breast fleshing would be diminished because of this association. The relationships presented here illustrate that the breast angle would be a more efficient criterion than breast width on the basis of the total correlations; however, the addition of body weight as a third variable actually would made breast width a more valuable measurement. A comparison of the relative weights that would be placed on body weight and breast measurement in selecting for breast fleshing is readily apparent from the standard partial regressions involving these characters. These regressions are: body weight and crosssectional area body weight and breast width body weight and breast angle body weight and Bird index
m'= .5851 a>'-f-.3779 V m'= .6769 w'+.3159
V
w ' = . 7 1 7 5 w'+. 1514 V m' = . 7856 w'+. 0701 b'
where m' is the weight of the breast in standard deviates, and w' and b' are the body weight and breast measurement respectively in standard deviates. The
657
constant associated with w' is the standard regression of breast meat on body weight independent of breast measurement, while the constant associated with breast measurement is the standard regression of breast meat on breast measurement independent of body weight. Thus in terms of standard measurement approximately 11 times as much weight would be placed on body weight as on the Bird index where both measurements are used in a selection program to improve breast fleshing. Only 1.5 times as much weight would be placed on body weight as on cross-sectional area where both of these measurements are used. A test of significance of the standard regressions of breast fleshing on breast measurement independent of body weight is a test of whether or not the multiple correlations are significantly different from the correlation between breast fleshing and body weight. The tests of significance by means of /.indicate that in no case are these standard regressions significant at the 5 percent level; although, the standard regressions involving the cross-sectional area and breast width are approaching significance at this level. The relatively limited gain in efficiency obtained by using a breast measurement in addition to body weight as a basis for appraising breast fleshing would seem to preclude the necessity for extensive or time-consuming breast measurements. Examination through handling is desirable from the standpoint of eliminating birds with crooked keels and other visible defects. If at the same time a quality score assigned on the basis of the apparent degree of breast fleshing were a reliable independent index of this fleshing, any need for further breast measurements might be eliminated. Although the correlation ratio between live handling score and weight of breast meat is .6833, the
658
W. L. BLOW AND E. W. GLAZENER
cockerels in grades 1, 2, and 3 weighed 54.7, 48.7, and 39.8 ounces respectively. This distribution indicates that handling quality is influenced in general to a considerable extent by live weight, and that the gain expected from additional information based on a handling score is inconsequential. The performance of this variable in multiple regression with live weight suggests that only an additional two percent of the variance in breast fleshing is accounted for by including handling score in the predictive equation. On the basis of these data the crosssectional breast area and breast width were the most desirable breast measurement when used in conjunction with body weight; however, the latter method has very distinct advantages because of its simplicity and rapidity in use. For these reasons breast width measured with calipers at a suitable distance above the keel appears to be the superior breast measurement for estimating breast fleshing in broilers. An appraisal of the different criteria naturally leads to the question of whether or not a breast measurement in addition to body weight is a worthwhile effort. This question can best be answered by pointing out the limited gain in precision effected by making the additional measurement. Broiler producers are still paid primarily for weight; and present grades, which supposedly reflect differences in fleshing, are largely determined by differrences in body weight. These factors are important considerations in determining whether or not a breeder is justified in expending considerable effort to improve the amount of breast fleshing. SUMMARY
Several criteria of conformation were used with 100 broiler New Hampshires to appraise the yield of breast meat in broilers. These criteria included breast width,
breast angle, cross-sectional breast area, the Bird index, handling quality, and body weight. Body weight appeared to be the superior single observation for evaluating the amount of breast fleshing. When the breast measurements were used singly in combination with body weight as a basis for selection, breast width and the crosssectional breast area had the highest relationship with the yield of breast meat. Breast width, because of the ease of measuring, was recommended for use in conjunction with body weight for selecting individuals with superior fleshing qualities. REFERENCES Bird, S., 1948. Quantitative determination and segregation of breast conformation in poultry. Poultry Sci. 27: 506-508. Doleck, R. L., W. O. Wilson and W. E. Poley, 1941. Physical measurements of carcass quality in roosters. Poultry Sci. 20: 161-170. Frischknecht, C. O., and M. A. Jull, 1946. Amount of breast meat and live and dressed grades in relation to body measurements in 12-week old purebred and crossbred chickens. Poultry Sci. 25:330-345. Gutteridge, H. S., and J. B. O'Neil, 1942. The relative effect of environment and heredity upon body measurements and production characteristics in poultry. I. Period of growth. Sci. Agr. 22: 378-389. Jaap, R. G., and R. Penquite, 1938. Criteria of conformation in market poultry. Poultry Sci. 17: 425-430. Jaap, R. G., and R. B. Thompson, 1940. Heritable differences in conformation of adult fowl. Poultry Sci. 19: 73-78. Lerner, I. M., V. S. Asmundson and D. M. Cruden, 1947. Poultry Sci. 26: 515-524. Maw, W. A., and A. J. G. Maw, 1938. The influence of type of sire on the body size of the progeny. U. S. Egg and Poultry Mag. 44: 78-84. Maw, W. A., and A. J. G. Maw, 1939. The relation of body measurements to the fattening grains and the percentage of edible flesh in the fowl. Sci. Agr. 19: 589-596. Scott, H. M., 1940. Checking market grades with meat measurements. U. S. Egg and Poultry Mag. 46:717-719.