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Relative Intra- and Inter-Stock Aggressiveness and Performance in the Domestic Fowl1
Relative Intra- and Inter-Stock Aggressiveness and Performance in the Domestic Fowl1 J . C. WOMACK,2 L. D . TlNDELL 3 AND R . E . COOK4 University of Georgia and United States Department of Agriculture (Received for publication May 15, 1965)
influenced by age or development; and (4) to determine whether recognition between birds of different breeds is on an individual or breed basis. STOCKS AND PROCEDURES
1 Journal Paper No. 434, College Experiment Station, University of Georgia, College of Agriculture Experiment Stations, Athens. Present Address: 2 Poultry Department, Virginia Polytechnic Institute, Blacksburg, Virginia. 3 Southern Regional Poultry Genetics Laboratory, ARS, Athens, Georgia. * Animal Husbandry Research Division, ARS, Beltsville, Maryland.
27
Females utilized in this study represented three commercial stocks and one experiment station stock of the White Leghorn (W.L.) breed and two experiment station stocks of the Rhode Island Red (R.I.R.) breed. Sixteen pullets represented each stock. Prior to housing, all pullets were reared in intermingled flocks, under range conditions. All pullets were housed at 20 weeks of age in ten-inch individual wire cages arranged in a linear fashion. The housing regime involved 16 replications of six birds each; all stocks being represented and randomly assigned within each block. Daily egg production records were maintained from housing (20 weeks) to 58 weeks of age. Data were collected on age at sexual maturity (age at first egg), survivor's and hen-housed percent egg production, mortality, body weight at 20 and 58 weeks of age, gains in weight; and egg weight, specific gravity and albumen height at 49 weeks of age. Relative aggressiveness was estimated from initial paired contests between strangers at 20, 38 and 56 weeks of age (trials one, two and three, respectively). Each pair of birds was tested in a neutral area (exhibition cage). Contests between birds were decided on the basis of fights, pecks and threat-avoidance interactions. As soon as a decision between two birds was reached, they were returned to
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
UMEROUS investigations have established that the peck order forms the basis of social organization in adult chickens. Sanctuary (1932) reported that hens in the upper half of the peck-order produce more eggs than do those composing the lower half of the social order. Intra-strain competition effects have also been reported by Masure and Allee (1934), Guhl (1953), Tindell and Craig (1959) and Tindell (1960). Evidence that breeds and strains of chickens differ in aggressiveness has been reported by Potter (1949), Holabird (1955), Hale (1956), Tindell and Craig (1959) and Tindell (1962). Conclusions concerning the degree of association of inter-strain aggressiveness and various performance traits are varied. In part, these differences in results may possibly be explained as being due to the diversity of techniques utilized in measuring aggressiveness. The present investigation was designed to: (1) determine if differences in relative aggressiveness are present among stocks; (2) to determine the relationship of relative intra- and inter-stock aggressiveness with various performance traits; (3) to determine if relative stock aggressiveness is
N
28
J . C. WOMACK, L . D . TlNDELL AND R . E . CoOK TABLE 1.—Correlations of individual intra-stock relative aggressiveness with various traits Correlation coefficients by s tockst
Range Trait Sexual maturity 20-week body weight 58-week body weight Gain in weight (20-58 weeks) Survivor's % egg production Hen-housed % egg production Egg weight Albumen height Specific gravity
d.f. 12-14 14 9-13 9-13 9-13 12-14 8-11 8-11 8-11
1 (W.L.) 2 (R.I.R.) -.34 .49 .05 .31 .01 .27 -.11 .15 .04
-.26 .68" -.11 -.06 .12 .48 .42 .36 -.36
3 (R.I.R.) 4 (W.L.) 5 (W.L.) .01 .67" -.41 -.23 -.39 -.01 .19 -.22 -.10
-.21 .38 .27 -.04 -.34 -.29 .08 .02 .34
-.48 .21 -.17 .40 .25 .42 -.11 -.28 -.25
Stocks pooled 6 (W.L.)
d.f.
r
- . 74" .40 -.25 -.44 .38 .60* -.31 .42 .00
78 84 71 71 68 78 60 60 60
-.20 .38" .00 -.14 .03 .26* .17 .10 .06
t Stocks 1, 2 and 3 are experiment station stocks; 4. 5 and 6 are commercial stocks. **P<.01. *P<.05.
RELATIVE INTRA-STOCK AGGRESSIVENESS AND PRODUCTIVITY Correlation coefficients of relative intrastock aggressiveness and various traits are given in Table 1. The correlations obtained for the six stocks were tested for heterogeneity using Fisher's r-z transformation in the chi-square test as given by Snedecor (19S6). All chi-square values were non-
significant indicating the correlations to be homogeneous; therefore, pooled correlation coefficients were calculated. Examination of the pooled intra-stock correlation coefficients, in Table 1, reveals a significant positive correlation between relative intra-stock aggressiveness and henhoused percent egg production. Initial body weight was positively correlated with relative aggressiveness at a highly significant level (P < .01). None of the other traits were significantly correlated with relative aggressiveness. The results in Table 1, therefore, indicate a tendency within a stock for the more aggressive hens to be heavier at 20 weeks of age (or for the heavier hens to be more aggressive) and to have a higher rate of egg production per hen housed from 20-58 weeks of age. RELATIVE INTER-STOCK AGGRESSIVENESS AND PRODUCTIVITY The average number of contests won by each stock in each trial is given in Table 2. Using Freidman's analysis of variance of TABLE 2.—Average number of contests won by : of each stock in each trial
Stock 1 2 3 4 5 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
Trial 1 Trial 2 Trial 3 (16 birds (10 birds (8 birds /stock) /stock) /stock)
_ X
2.90 1.10 0.80 3.30 3.90 3.00
2.68 1.01 0.91 3.39 3.95 3.06
2.87 0.94 0.44 3.63 4.06 3.06
2.25 1.00 1.50 3.25 3.88 3.12
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
their home cages. If a decision was not observed within the initial ten minute observation period, the birds were returned to their cages and subsequently tested until the more aggressive bird could be determined. All birds within each of the 16 replications were tested with each other in trial one in order to determine relative inter-stock aggressiveness. Only complete replications were used in subsequent trials. In determining intra-stock aggressiveness all birds within a stock met in paired contests. Correlation coefficients between relative aggressiveness and various traits were calculated on an intra- and inter-stock basis. Associations of relative intra- and interstock aggressiveness and performance were estimated by correlating the average number of contests won in the three trials with the various performance traits. However, sexual maturity and 20-week body weight were correlated with relative aggressiveness using only the number of contests won in the initial trial.
29
AGGRESSIVENESS AND PERFORMANCE
T A B L E 3.—Average inter-stock
Stock 1 2 3 4 S 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
1 2 3 4 5 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
T A B L E 4.—Correlations of relative inter-stock aggressiveness with various traits All stocks
Sexual maturity 20-week body weight 58-week body weight Gain in weight (20-58 weeks) Survivor's % egg production Hen-housed % egg production Percent mortality Egg weight Specific gravity Albumen height
Four W.L. stocks
d.f.
r
d.f.
r
4 4 4 4 4
-.15 -.89» -.94"
2 2 2
-.78 .29 -.32
-.94"
2
-.69
.67
2
.94
.79 -.76 .36 .35 -.18
2 2 2 2 2
-.94 -.86 -.07 .46
4 4 4 4 4
"P<.01. •P<.05.
in between the W.L. stocks (such was not the case here), individual recognition would be established, at least on the part of the R.I.R. The average performance of the stocks for various traits is shown in Table 3. As you might expect, the two R.I.R. stocks were considerably heavier than the W.L. stocks at 20 and 58 weeks of age. They also had greater weight gains from 20-58 weeks of age. Since these two R.I.R. stocks were also the least aggressive stocks, their contributions to the correlations of relative aggressiveness and body weight involving all six stocks would be expected in performance for various
traits
Ave. no. contests won
Sexual maturity
20-wk. body weight
58-wk. body weight
Weight gained
Survivor's %egg production
2.68 1.01 0.91 3.39 3.95 3.06
170 161 163 159 161 163
1,611 2,322 2,171 1,754 1,643 1,660
2,003 2,942 2,795 2,183 1,886 2,026
401 569 566 416 263 325
50 55 54 61 65 59
Hen-housed % production
mortality
%
Egg weight
Specific gravity
Albumen height
47 50 47 58 61 55
12.50 12.50 31.25 6.25 6.25 12.50
62 62 62 66 62 64
1.080 1.079 1.078 1.071 1.078 1.073
6.0 6.0 6.3 5.6 6.4 6.0
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
ranks as described by Siegel (1956), highly significant (P < .01) differences in relative aggressiveness were found to exist among the six stocks in each trial. This indicates that genetic variability in relative aggressiveness was present among the different stocks. As shown, the most aggressive stock in each trial was stock five (W.L.). The relative order of aggressiveness of the stocks remained the same in each trial except for stocks two and three (R.I.R.) which switched positions in the third trial. This tends to indicate that relative stock aggressiveness was not, in general, influenced by age. The two R.I.R. stocks were the least aggressive of the six stocks in each of the three trials, possibly indicating that recognition between birds is on a breed basis instead of an individual basis. The question of whether individual or breed recognition was more important is confounded by the fact that the two R.I.R. stocks were the least aggressive. If aggressiveness per se of these two stocks is accurately reflected, then one would expect these two stocks to be at the bottom of the social order, regardless of the type of recognition. If, however, the two R.I.R. stocks had ranked
30
J . C. WOMACK, L . D . TlNDELL AND R . E . COOK
SUMMARY Significant differences in relative aggressiveness were found to exist among six stocks of chickens representing the White Leghorn and Rhode Island Red breeds. Relative stock aggressiveness did not change materially with age. Relative intra-stock aggressiveness was significantly correlated (in a positive direction) with 20-week body weight and percent hen-housed egg production. Significant negative correlations were found to exist between relative inter-stock aggressiveness and 20-week body weight,
58-week body weight, and weight gained from 20-58 weeks of age. The effect of the two R.I.R. stocks on the magnitude and direction of these correlations is discussed. Although not significant, higher ranking stocks tended to have higher survivor's and hen-housed percent egg production and less mortality than less aggressive stocks. REFERENCES Guhl, A. M., 1953. Social behavior of the domestic fowl. Kansas Agr. Expt. Sta. Techn. Bui. 73: 1-48. Hale, E. B., 1956. Breed recognition in the social interaction of domestic fowl. Behavior, 10: 240-253. Holabird, C , 1955. Social organization in flocks of Light Brahma hens as compared with other breeds. Physiol. Zool. 28: 239-255. Masure, R. H. and W. C. Allee, 1934. The social order in flocks of the common chicken and pigeon. Auk, 51: 306-32S. Potter, J. H., 1949. Dominance relations between different breeds of domestic hens. Physiol. Zool. 26: 147-161. Sanctuary, W. C , 1932. A study of avian behavior to determine the nature and persistency of the order of dominance in the domestic fowl and to relate these to certain physiological reactions. M. S. Thesis, Mass. State College, Amherst. Siegel, S., 1956. Nonparametric Statistics for the Behavioral Sciences. McGraw-Hill Book Co., Inc., New York. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames. Tindell, D., and J. V. Craig, 1959. Effects of social competition on laying house performance in the chicken. Poultry Sci. 38: 95-105. Tindell, D., 1960. Genetic variation in social aggressiveness and competition effects between sire families in small flocks of chickens. Poultry Sci. 39: 1318-1320. Tindell, D., 1962. Inter-strain aggressiveness and performance in chickens. Poultry Sci. 4 1 : 19541956.
MARCH 23-25. ANNUAL MEETING, GRAIN AND FEED DEALERS NATIONAL ASSOCIATION, EDGEWATER BEACH HOTEL, CHICAGO, ILL.
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
the negative direction. Significant and highly significant negative correlations were found to exist (Table 4) between relative inter-stock aggressiveness and 20-week body weight, 58-week weight and weight gained. Removal of the two R.I.R. stocks resulted in a non-significant positive correlation of .29 (aggressiveness and 20-week weight) which, in general, agrees with previous investigations. The magnitude of the correlations of aggressiveness with 58-week body weight and weight gained was reduced when the R.I.R. stocks were removed from the analysis, but were still negative, though not significant statistically. Positive correlations approaching significance were present for relative aggressiveness of the six stocks and survivors's and hen-housed percent egg production. A negative correlation of large magnitude was indicated between relative inter-stock aggressiveness and percent mortality. These correlations were accentuated to a much greater extent when only the four W.L. stocks were considered.
influenced by age or development; and (4) to determine whether recognition between birds of different breeds is on an individual or breed basis. STOCKS AND PROCEDURES
1 Journal Paper No. 434, College Experiment Station, University of Georgia, College of Agriculture Experiment Stations, Athens. Present Address: 2 Poultry Department, Virginia Polytechnic Institute, Blacksburg, Virginia. 3 Southern Regional Poultry Genetics Laboratory, ARS, Athens, Georgia. * Animal Husbandry Research Division, ARS, Beltsville, Maryland.
27
Females utilized in this study represented three commercial stocks and one experiment station stock of the White Leghorn (W.L.) breed and two experiment station stocks of the Rhode Island Red (R.I.R.) breed. Sixteen pullets represented each stock. Prior to housing, all pullets were reared in intermingled flocks, under range conditions. All pullets were housed at 20 weeks of age in ten-inch individual wire cages arranged in a linear fashion. The housing regime involved 16 replications of six birds each; all stocks being represented and randomly assigned within each block. Daily egg production records were maintained from housing (20 weeks) to 58 weeks of age. Data were collected on age at sexual maturity (age at first egg), survivor's and hen-housed percent egg production, mortality, body weight at 20 and 58 weeks of age, gains in weight; and egg weight, specific gravity and albumen height at 49 weeks of age. Relative aggressiveness was estimated from initial paired contests between strangers at 20, 38 and 56 weeks of age (trials one, two and three, respectively). Each pair of birds was tested in a neutral area (exhibition cage). Contests between birds were decided on the basis of fights, pecks and threat-avoidance interactions. As soon as a decision between two birds was reached, they were returned to
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
UMEROUS investigations have established that the peck order forms the basis of social organization in adult chickens. Sanctuary (1932) reported that hens in the upper half of the peck-order produce more eggs than do those composing the lower half of the social order. Intra-strain competition effects have also been reported by Masure and Allee (1934), Guhl (1953), Tindell and Craig (1959) and Tindell (1960). Evidence that breeds and strains of chickens differ in aggressiveness has been reported by Potter (1949), Holabird (1955), Hale (1956), Tindell and Craig (1959) and Tindell (1962). Conclusions concerning the degree of association of inter-strain aggressiveness and various performance traits are varied. In part, these differences in results may possibly be explained as being due to the diversity of techniques utilized in measuring aggressiveness. The present investigation was designed to: (1) determine if differences in relative aggressiveness are present among stocks; (2) to determine the relationship of relative intra- and inter-stock aggressiveness with various performance traits; (3) to determine if relative stock aggressiveness is
N
28
J . C. WOMACK, L . D . TlNDELL AND R . E . CoOK TABLE 1.—Correlations of individual intra-stock relative aggressiveness with various traits Correlation coefficients by s tockst
Range Trait Sexual maturity 20-week body weight 58-week body weight Gain in weight (20-58 weeks) Survivor's % egg production Hen-housed % egg production Egg weight Albumen height Specific gravity
d.f. 12-14 14 9-13 9-13 9-13 12-14 8-11 8-11 8-11
1 (W.L.) 2 (R.I.R.) -.34 .49 .05 .31 .01 .27 -.11 .15 .04
-.26 .68" -.11 -.06 .12 .48 .42 .36 -.36
3 (R.I.R.) 4 (W.L.) 5 (W.L.) .01 .67" -.41 -.23 -.39 -.01 .19 -.22 -.10
-.21 .38 .27 -.04 -.34 -.29 .08 .02 .34
-.48 .21 -.17 .40 .25 .42 -.11 -.28 -.25
Stocks pooled 6 (W.L.)
d.f.
r
- . 74" .40 -.25 -.44 .38 .60* -.31 .42 .00
78 84 71 71 68 78 60 60 60
-.20 .38" .00 -.14 .03 .26* .17 .10 .06
t Stocks 1, 2 and 3 are experiment station stocks; 4. 5 and 6 are commercial stocks. **P<.01. *P<.05.
RELATIVE INTRA-STOCK AGGRESSIVENESS AND PRODUCTIVITY Correlation coefficients of relative intrastock aggressiveness and various traits are given in Table 1. The correlations obtained for the six stocks were tested for heterogeneity using Fisher's r-z transformation in the chi-square test as given by Snedecor (19S6). All chi-square values were non-
significant indicating the correlations to be homogeneous; therefore, pooled correlation coefficients were calculated. Examination of the pooled intra-stock correlation coefficients, in Table 1, reveals a significant positive correlation between relative intra-stock aggressiveness and henhoused percent egg production. Initial body weight was positively correlated with relative aggressiveness at a highly significant level (P < .01). None of the other traits were significantly correlated with relative aggressiveness. The results in Table 1, therefore, indicate a tendency within a stock for the more aggressive hens to be heavier at 20 weeks of age (or for the heavier hens to be more aggressive) and to have a higher rate of egg production per hen housed from 20-58 weeks of age. RELATIVE INTER-STOCK AGGRESSIVENESS AND PRODUCTIVITY The average number of contests won by each stock in each trial is given in Table 2. Using Freidman's analysis of variance of TABLE 2.—Average number of contests won by : of each stock in each trial
Stock 1 2 3 4 5 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
Trial 1 Trial 2 Trial 3 (16 birds (10 birds (8 birds /stock) /stock) /stock)
_ X
2.90 1.10 0.80 3.30 3.90 3.00
2.68 1.01 0.91 3.39 3.95 3.06
2.87 0.94 0.44 3.63 4.06 3.06
2.25 1.00 1.50 3.25 3.88 3.12
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
their home cages. If a decision was not observed within the initial ten minute observation period, the birds were returned to their cages and subsequently tested until the more aggressive bird could be determined. All birds within each of the 16 replications were tested with each other in trial one in order to determine relative inter-stock aggressiveness. Only complete replications were used in subsequent trials. In determining intra-stock aggressiveness all birds within a stock met in paired contests. Correlation coefficients between relative aggressiveness and various traits were calculated on an intra- and inter-stock basis. Associations of relative intra- and interstock aggressiveness and performance were estimated by correlating the average number of contests won in the three trials with the various performance traits. However, sexual maturity and 20-week body weight were correlated with relative aggressiveness using only the number of contests won in the initial trial.
29
AGGRESSIVENESS AND PERFORMANCE
T A B L E 3.—Average inter-stock
Stock 1 2 3 4 S 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
1 2 3 4 5 6
(W.L.) (R.I.R.) (R.I.R.) (W.L.) (W.L.) (W.L.)
T A B L E 4.—Correlations of relative inter-stock aggressiveness with various traits All stocks
Sexual maturity 20-week body weight 58-week body weight Gain in weight (20-58 weeks) Survivor's % egg production Hen-housed % egg production Percent mortality Egg weight Specific gravity Albumen height
Four W.L. stocks
d.f.
r
d.f.
r
4 4 4 4 4
-.15 -.89» -.94"
2 2 2
-.78 .29 -.32
-.94"
2
-.69
.67
2
.94
.79 -.76 .36 .35 -.18
2 2 2 2 2
-.94 -.86 -.07 .46
4 4 4 4 4
"P<.01. •P<.05.
in between the W.L. stocks (such was not the case here), individual recognition would be established, at least on the part of the R.I.R. The average performance of the stocks for various traits is shown in Table 3. As you might expect, the two R.I.R. stocks were considerably heavier than the W.L. stocks at 20 and 58 weeks of age. They also had greater weight gains from 20-58 weeks of age. Since these two R.I.R. stocks were also the least aggressive stocks, their contributions to the correlations of relative aggressiveness and body weight involving all six stocks would be expected in performance for various
traits
Ave. no. contests won
Sexual maturity
20-wk. body weight
58-wk. body weight
Weight gained
Survivor's %egg production
2.68 1.01 0.91 3.39 3.95 3.06
170 161 163 159 161 163
1,611 2,322 2,171 1,754 1,643 1,660
2,003 2,942 2,795 2,183 1,886 2,026
401 569 566 416 263 325
50 55 54 61 65 59
Hen-housed % production
mortality
%
Egg weight
Specific gravity
Albumen height
47 50 47 58 61 55
12.50 12.50 31.25 6.25 6.25 12.50
62 62 62 66 62 64
1.080 1.079 1.078 1.071 1.078 1.073
6.0 6.0 6.3 5.6 6.4 6.0
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
ranks as described by Siegel (1956), highly significant (P < .01) differences in relative aggressiveness were found to exist among the six stocks in each trial. This indicates that genetic variability in relative aggressiveness was present among the different stocks. As shown, the most aggressive stock in each trial was stock five (W.L.). The relative order of aggressiveness of the stocks remained the same in each trial except for stocks two and three (R.I.R.) which switched positions in the third trial. This tends to indicate that relative stock aggressiveness was not, in general, influenced by age. The two R.I.R. stocks were the least aggressive of the six stocks in each of the three trials, possibly indicating that recognition between birds is on a breed basis instead of an individual basis. The question of whether individual or breed recognition was more important is confounded by the fact that the two R.I.R. stocks were the least aggressive. If aggressiveness per se of these two stocks is accurately reflected, then one would expect these two stocks to be at the bottom of the social order, regardless of the type of recognition. If, however, the two R.I.R. stocks had ranked
30
J . C. WOMACK, L . D . TlNDELL AND R . E . COOK
SUMMARY Significant differences in relative aggressiveness were found to exist among six stocks of chickens representing the White Leghorn and Rhode Island Red breeds. Relative stock aggressiveness did not change materially with age. Relative intra-stock aggressiveness was significantly correlated (in a positive direction) with 20-week body weight and percent hen-housed egg production. Significant negative correlations were found to exist between relative inter-stock aggressiveness and 20-week body weight,
58-week body weight, and weight gained from 20-58 weeks of age. The effect of the two R.I.R. stocks on the magnitude and direction of these correlations is discussed. Although not significant, higher ranking stocks tended to have higher survivor's and hen-housed percent egg production and less mortality than less aggressive stocks. REFERENCES Guhl, A. M., 1953. Social behavior of the domestic fowl. Kansas Agr. Expt. Sta. Techn. Bui. 73: 1-48. Hale, E. B., 1956. Breed recognition in the social interaction of domestic fowl. Behavior, 10: 240-253. Holabird, C , 1955. Social organization in flocks of Light Brahma hens as compared with other breeds. Physiol. Zool. 28: 239-255. Masure, R. H. and W. C. Allee, 1934. The social order in flocks of the common chicken and pigeon. Auk, 51: 306-32S. Potter, J. H., 1949. Dominance relations between different breeds of domestic hens. Physiol. Zool. 26: 147-161. Sanctuary, W. C , 1932. A study of avian behavior to determine the nature and persistency of the order of dominance in the domestic fowl and to relate these to certain physiological reactions. M. S. Thesis, Mass. State College, Amherst. Siegel, S., 1956. Nonparametric Statistics for the Behavioral Sciences. McGraw-Hill Book Co., Inc., New York. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames. Tindell, D., and J. V. Craig, 1959. Effects of social competition on laying house performance in the chicken. Poultry Sci. 38: 95-105. Tindell, D., 1960. Genetic variation in social aggressiveness and competition effects between sire families in small flocks of chickens. Poultry Sci. 39: 1318-1320. Tindell, D., 1962. Inter-strain aggressiveness and performance in chickens. Poultry Sci. 4 1 : 19541956.
MARCH 23-25. ANNUAL MEETING, GRAIN AND FEED DEALERS NATIONAL ASSOCIATION, EDGEWATER BEACH HOTEL, CHICAGO, ILL.
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 20, 2015
the negative direction. Significant and highly significant negative correlations were found to exist (Table 4) between relative inter-stock aggressiveness and 20-week body weight, 58-week weight and weight gained. Removal of the two R.I.R. stocks resulted in a non-significant positive correlation of .29 (aggressiveness and 20-week weight) which, in general, agrees with previous investigations. The magnitude of the correlations of aggressiveness with 58-week body weight and weight gained was reduced when the R.I.R. stocks were removed from the analysis, but were still negative, though not significant statistically. Positive correlations approaching significance were present for relative aggressiveness of the six stocks and survivors's and hen-housed percent egg production. A negative correlation of large magnitude was indicated between relative inter-stock aggressiveness and percent mortality. These correlations were accentuated to a much greater extent when only the four W.L. stocks were considered.