- Email: [email protected]
Endocrine Responses of Six Stocks of Chickens Reared at Different Population Densities
PREDNISOLONE IN NUCLEIC ACID SYNTHESIS
grande for technical assistance during the course of this investigation. The work was supported by Institution Grant from the American Cancer Society. REFERENCES
lymphoid tissues and their dependence on protein synthesis. Fed. Proc. 23: 481. Hymer, W. C , and E. L. Kuff, 1965. Isolation of nuclei from mammalian tissues through the use of triton X-100. J. Histochem. Cytochem. 12: 359-363. Kirby, K. S., 1957. A new method for the isolation of deoxyribonucleic acids. Biochem. J. 66: 495504. Lang, N., and C. E. Sekeris, 1964. Zum Wirkungsmechanismus der Hormone: Z. Physiol. Chem. 339: 238-248. Nakagawa, S., and A. White, 1967. Response of rat thymic nuclear RNA polymerase to Cortisol injection. Endocrinol. 81: 861-870. Pratt, W. B., and L. Aronow, 1966. The effect of glucocorticoids on protein and nucleic acid synthesis in mouse fibroblasts growing in vitro. J. Biol. Chem. 241: 5244-5250. Scherrer, K., and J. E. Darnell, 1966. Sedimentation characteristics of rapidly labelled RNA from HeLa cells. Biochemical Biophysical Res. Comm. 7: 486^190. Stevens, W., C. Colessides and T. F. Dougherty, 1966. A time study on the effect of Cortisol on the incorporation of thymidine-2- u C into nucleic acids of mouse lymphatic tissue. Endocrinol. 78: 600-604. Weber, G. A., S. Srivastava and R. L. Singhal, 1965. Role of enzymes in homeostasis VLTI. Early effects of corticosteroid hormones in hepatic gluconeogenic enzymes, ribonucleic acid metabolism and amino acid level. J. Biol. Chem. 240: 750-756.
Endocrine Responses of Six Stocks of Chickens Reared at Different Population Densities P . B . SlEGEL AND H . S. SlEGEL 1 Virginia Polytechnic Institute, Blacksburg, Virginia 24061 (Received for publication March 8, 1969)
D
URING the past decade randombred populations have come into use as genetic and environmental controls in poultry experiments. In order for a 1 Present address: Southeast Poultry Research Laboratory, Athens, Ga.
population to be an adequate environmental control, its response to treatments should be consistent with that of other populations in the experiment. Homeostatic mechanisms (Lerner, 1954) may enable randombred populations to be better buffered to environmental changes
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
Bellamy, D., and R. Leonard, 1965. Effect of Cortisol on the growth of chicks. Gen. Comp. Endocrinol. 5:402^10. Bethell, J., H. Feigelson and P. Feigelson, 1965. The differential effects of glucocorticoids on tissue and plasma amino acid levels. Biochem. et Biophys. Acta, 104: 92-97. Bottoms, G., and D. D. Goetsch, 1967. Subcellular distribution of the (3H) corticosterone fraction in brain, thymus, heart, and liver of the rat. Proc. Soc. Exptl. Biol. Med. 124: 662-665. Bottoms, G. D., and D. D. Goetsch, 1968. Effects of corticosterone on oxidative metabolism in different tissues of the rat. Gen. Comp. Endocrinol. 10: 310-314. Burton, K., 1955. A study of the conditions and mechanism of the diphenylamine reaction for the colorimetric estimation of deoxyribonucleic acid. Biochem. J. 62: 315-323. Ceriotti, G., 1955. Determination of nucleic acids in animal tissues. J. Biol. Chem. 214: 59-70. Dougherty, T. F., and A. White, 1945. Functional alterations in lymphoid tissue induced by adrenal cortical secretion. Am. J. Anat. 77: 81-110. Feigelson, M., 1964. Cortisone induced alterations in purine and RNA metabolism in liver and
1425
1426
P. B. SIEGEL AND H. S. SIEGEL
Tests to study genotype-environment interactions of various stocks maintained at several locations at two population den-
sity levels were conducted as part of the Southern Regional Poultry Breeding Project (Tindell et al., 1968). Reported herein are differences in adrenal weights and functional activity among six of these stocks that were maintained at the two density levels at the Virginia station. MATERIALS AND METHODS
Experimental procedures were similar for the two trials which commenced May 24, 1962 and May 17, 1963. Eggs from each of ten stocks were sent by cooperators of the SRPB project to the Southern Regional Poultry Genetics Laboratory at Athens, Georgia, for incubation. Upon hatching, samples of chicks from each stock were shipped from that laboratory to ours where the experiments reported here were conducted. Endocrine data were obtained from six of the 10 stocks. Stocks. Lines sampled both years were: (1) North Carolina Rhode Island Red (NCRIR), (2) Mississippi New Hampshire Red (MNHR), (3) Louisiana Randombred (LRB), (4) Virginia High Weight White Plymouth Rock (VWR), (5) Athens-Canadian Randombred (ACRB), and (6) Athens Randombred (ARB). Descriptions of the first three populations were provided by their developers (W. L. Blow, L. J. Dressen, and W. A. Johnson). The NCRIR maintained at the Willard sub-station has been a closed population since at least 1946 with the exception of an introduction of some inbreds in 1956. The MNHR, a closed population since 1952, had undergone fairly intensive selection for body weight at 8 weeks of age since 1956. The LRB is a random mating population of about 25 males and 200 females established in 1954 from White and Dark Cornish, Buff Orpington, and White Leghorn populations. Siegel (1962) has described the VWR while Hess (1962) described the ACRB and ARB.
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
and might result in their being less sensitive to particular treatments than nonrandombred stocks. This lack of sensisitivity, in comparison to closed populations, might render randombreds less effective as environmental controls in certain situations. The influence of population density on certain endocrine responses has been demonstrated in several species (e.g. Christian, 1950, 1955; Siegel, 1960; Thiessen and Rogers, 1961; Christian and Davis, 1964). Differences have been shown in the endocrine response of laboratory and wild mice to population pressures (Christian, 1955) as well as species-density interactions (Bronson, 1963). Environmental improvements of poultry housing have resulted in increased numbers of chickens raised per unit area. Siegel (1960) found no consistent effects of population density on endocrine function in chickens to 11 weeks of age but afterwards increased density resulted in heavier adrenals and lower concentrations of adrenal cholesterol. Experiments with other species (Clarke, 1953; Davis and Christian, 1957; Vandenbergh, 1960) have suggested that the occurrence of agonistic behavior may be as important as increased population density in the manifestation of certain physiological changes. Although peckrights are not established in flocks of chickens until about 11 weeks of age (Guhl, 1964) agonistic behavior occurs prior to this age and peaks at about 8 weeks (Dawson and Siegel, 1967). Thus, the physiological effects of increased population densities may not be strongly manifested prior to this time. Also, chickens may be less responsive to such stimulation than mammals (Siegel and Siegel, 1961).
ENDOCRINE RESPONSE AND STOCKS
and corticosteroid concentrations (per gland and as fig. per mg. of adrenal). RESULTS AND DISCUSSION
Means and standard errors of the traits measured have been summarized within trials by stock and sex and are presented in Tables 1, 2, 3 and 4. Population density. No significant differences were found between birds maintained at the two floor space allowances for any of the traits measured with the exception of adjusted left adrenal weight in trial 1 where mean weights were 4.11 mg./lOO g. body weight at 464.5 cm.2 of floor space and 3.83 at the 929 cm.2 allowance. The lack of any consistent effect of population density on body weight under our conditions was consistent with that observed in the overall experiment by Tindell et al. (1968). The results for endocrine weights and adrenal cholesterol concentrations were consistent with those of Siegel (1960) who reported no effect to 11 weeks of age. They also support findings with other species (Clarke, 1953; Davis and Christian, 1957; Vandenbergh, 1960) in that the occurrence of agonistic behavior may be as important as population density in the manifestation of the physiological changes. Although the birds in our experiment did exhibit some agonistic behavior they were sacrificed during the early stages of the establishment of peckrights. Sex. Sexual dimorphism was observed for all weight characteristics and total adrenal cholesterol concentration with means for males being significantly higher than those for females. Sexual dimorphism was not found when adrenal cholesterol concentration was expressed at jug./mg. of gland or for corticosterone. Stocks. Significant differences were evi-
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
Management. Male and female chicks from the six stocks plus the other four stocks (not reported here) were intermingled in duplicate pens at each of two population densities. A total of 548 and 496 chicks were started in trials 1 and 2, respectively, with an equal number of birds started in each pen within each trial. Pens were modified so that half of the chicks were started at a floor space allowance of 464.5 cm2, and the other half at 929 cm2. An adjustment in floor space for mortality was made at 4 weeks of age. Chicks were placed m pens two days after hatching and remained there until the experiment was terminated 8 weeks later. A practical-type broiler diet was fed. Lighting was continuous and feeders consisted of three 36.8 cm. diameter tubes per pen and watering allowances were 1.3 cm. per chick started. Measurements. At 57 days of age 3 males and 3 females per treatment pen were selected for measurements of adrenal weight, adrenal cholesterol and corticosterone concentration. The procedure for both trials consisted of weighing chicks to the nearest gram and then sacrificing them by bleeding. Adrenal glands were removed, weighed separately to the nearest 0.1 mg., and immediately frozen for subsequent cholesterol and corticosterone determinations. The left gland was used for measurement of cholesterol (Knobil et al., 1954) and the right one for corticosterone (Guillemin et al., 1959). Statistical analyses were made on an intra-trial basis using a factorial analysis. Stocks, floor space levels, sex, and replicates were considered main effects and the appropriate interactions calculated, and means separated by Duncan's multiple range test. Analyses were made for body weight; left, right and total adrenal weight (unadjusted and adjusted to 100 g. of body weight); adrenal cholesterol;
1427
d"c? 9 9
&
R. adr. wt. (mg.)
L. adr. wt. (mg.)
T. adr. wt. (mg.)
R. adr. wt. (mg./lOO g.)
L. adr. wt. (mg./lOO g.)
T. adr. wt. (mg./lOO g.)
(2.1) (2.2)
82.9" 60.9"
7.63" (.26) 7.67" b (.34)
3.59" (.17) 3.58" b (.17)
4.04" (.14) 4.09»b (.24)
(1.4) (1.2)
(1.2) (1.7)
38.9" 28.4"
44.0» 32.5"
l,099" b (43) 801" (23)
NCRIR 1 (61) (44)
(3.9) (2.6)
(.33) (.18)
(.35) (.14)
8.25»b (.66) 6.87" (.23)
3.94" 3.25"
4.31" b 3.62"
118.2° (7.1) 81.6 b ° (4.4)
56.7° 38.4 b
61.5" (3.4) 43.2 b ° (2.7)
l^&P 1,186"
MNHR 2
(.46) (.14)
10.30° 8.47"
(.78) (.31)
4.90" (.35) 3.94" b (.22)
5.40° 4.53 b
115.8° (6.6) 82.9 b ° (4.2)
8.98" b (.27) 7.02" (.28)
4.28" b (.19) 3.34" b (.11)
4.70" bc (.18) 3.68" (.22)
104.8b° (3.4) 73.9b° (3.5)
50.2 b ° (2.6) 35.1" b (1.2)
(3.0) (2.3)
55.1° 38.4 b
54.61* (2.1) 38.8"°° (2.6)
l,182 b ° (50) l,052 b (27)
VWR 4
60.7^ (4.2) 44.5 b ° f2.3)
1,143"^ (32) 979» (34)
LRB 3
Stock
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
cfcf 9 9
Sex
Body wt. (g.)
Trait
TABLE 1.—Means and standard errors ( ) of body and gland weights by sex
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
9 9
9 9
L. adr. wt. (mg./lOO g.)
T. adr. wt. (mg./lOO g.)
3.98"" (.22) 3.65"" (.16) 4.02"° (.15) 3.26" (.15) 8.00"° (.39) 6.91" (.28)
4.24"" (.46) 3.93"" (.22) (.54) (.23)
3.82" 4.27" 8.06"° (.78) 8.20" (.40)
3.42" (.46) 3.62"" (.22) 3.32" (.54) 3.81"" (.23) 6.74" (.78) 7.44«" (.40)
3.84"" (.24) 3.34" (.25)
3.85"" (.16) 3.48" (.34)
7.69" 6.82"
(.34) (.43)
105.3° (5.7) 73.1"° (2.9)
88.8""° (4.4) 75.5"° (2.9)
97.1"° (4.4) 82.1° (2.9)
76.9" 57.6"
(2.7) (2.8)
52.4° (3.0) 38.6"° (1.6)
1,316° (32) l,058°d (26)
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
9 9
9 9
R. adr. wt. (mg./lOO g.)
T. adr. wt. (mg.)
46.6"° (2.6) 36.4"° (2.0)
1,138" (48) 926"" (35)
VWR 4
52.9° (2.8) 34.5"" (1.8)
(2.9) (2.0)
(48) (35)
49.3"° (2.6) 40.2° (2.0)
l,436 d 1,103d
LRB 3
42.2"" (2.5) 39.1"° (1.3)
38.6" 29.6"
cfb 1 9 9
L. adr. wt. (mg.)
(1-9) (1.7)
(20) (33)
MNHR 2
Stock
47.8"° (2.5) 41.9° (1.3)
38.3" 28.0"
1,055" 856"
NCRIR 1
cfcf 9 9
9 9
Sex
R. adr. wt. (mg.)
Body wt. (g.)
Trait
1
TABLE 2.—Means and standard errors ( ) of body and gland weights by sex a
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
3.33" 2.58"
d'd 1 9 9
(.31) (.25)
(.13) (.07) 2.59" 3.42"
1.59" 1.42" (.19) (.30)
2.13" 2.99"
(.21) (.20)
2.76" 3.02"
(.27) (.36)
(.13) (.13)
1.49" 1.15"
1.28" 1.32"
(.12) (.09)
(.14) (.11)
20.9"" (1.2) 21.7" (1.0)
23.6"" (1.0) 21.6" (1.2)
1,025"" (43) 764"" (49)
1,282"" (60) 835" (80)
(1.6) (1.0)
(155) (50)
VWR 4
LRB 3
Stock
9 9
Adr. cholesterol. (Total Mg.)
(82) (51)
(1.4) (1.6)
(.10) (.07)
(.28) (.32)
647" 520"
17.0" 17.7"
1.32" 1.21"
3.84" 4.04"
NCRIR 1
3.24" 3.50"
(.27) (.54)
3.58" 4.20"
(.21) (.19)
3.09" 3.76"
1.68" 1.35"
(.12) (.16)
1.64" 1.47"
(.11) (.11)
1.52" 1.49"
(.23) (.23)
(.13) t.ll)
(1.6) (2.2)
973"" (86) 810" (108)
VWR 4
18.6" 22.9"
(2.3) (2.2)
30.6" 30.0"
893"" (110) 640"" (103)
LRB 3
21.3"" (2.3) 16.2" (2.2)
(110) (103)
1,433d 1,260=
MNHR 2
Stock
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
0«. %)
9 9
9 9
Adr. corticos. (Total Mg.)
Adr. corticos.
9 9
(/Ltg./mg.)
Adr. cholesterol
Sex
Trait
TABLE 4.—Means and standard errors ( ) of adrenal cholesterol and corticosterone b
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
0«. %)
Adr. corticos.
1.46" .82"
9 9
Adr. corticos. (Total /ig.)
24.8" 43.2"
22.8«b (3.3) 20.7" (1.2)
9 9
Adr. cholesterol (Mg-/mg.)
1,428" 879"
MNHR 2
(115) (28)
872" 578"
NCRIR 1
9 9
Sex
(Total „g.)
Adr. cholesterol
Trait
TABLE 3.—Means and standard errors ( ) of adrenal cholesterol and corticosterone b
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
E N D O C R I N E R E S P O N S E AND STOCKS
Adrenal weight. There was a positive association between adrenal weight and body weight in the relative rankings of the stocks. T h e N C R I R consistently had the lightest adrenal glands followed by the A C R B . Fluctuations in rankings for adrenal weights varied among the other four stocks depending on the sex and trial. R a n k correlations between mean adrenal weights unadjusted for body weight and those expressed as mg./lOO g. of body weight were, in most instances, of a low magnitude. Using total adrenal weight as a n example, the rank correlations between adjusted and unadjusted values were .20 a n d .32 for males and females, respectively, in trial 1 and —.14 for males and .72 for females in trial 2. T h u s , comparisons among stocks for adrenal weight should be more meaningful when expressed as per 100 g. of body weight. Significant differences were found among stocks for adrenal weight expressed as mg./lOO g. of body weight. Weights for the three randombred populations appeared to be heavier than those for the selected ones, although differences were not always significant. Among the selected populations there were no significant dif-
ferences between the N C R I R and the VWR. Means for the M N H R were of a similar magnitude to the other selected populations, with the exception of the males in trial 2 where the weights for the left and both glands were significantly lower. Adrenal cholesterol and corticosterone. Cholesterol content of the left adrenal gland expressed either as total or fig./ mg. of gland was highest in the M N H R . Conversely, the N C R I R was consistently among the lower ranking stocks for this characteristic. T h e other nonrandombred population, the V W R , ranked intermediate to the M N H R and the N C R I R . No significant difference existed in either trial among the randombred females for cholesterol concentration. Among males, levels were significantly higher for the A R B than for the A C R B in three of four comparisons, while means for the L R B were intermediate to the other randombreds. No significant differences were found among stocks or between floor space treatments for corticosterone. Interactions. T h e interaction, sex-floor space, was not significant for any trait measured in either trial. Further, in only 1 of the 22 analyses of variance made was the stock-floor space interaction significant. The exception, adjusted adrenal weight in trial 2, was probably a chance occurrence. These results suggest t h a t both sexes and all stocks responded in a similar manner to 8 weeks of age at both population densities. Although significant stock-sex interactions were not observed in trial 1, several were observed in trial 2. These were for body weight, left adrenal weight (adjusted and unadjusted for body weight) and for total adrenal weight adjusted for body weight. Stock-sex interactions m a y be expected when the sexual dimorphism is not the same for all stocks as shown in
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
d e n t among stocks for all characteristics within each trial, with the exception of corticosterone. Ranking of stocks within sexes between years were consistent. Body weight. T h e heaviest stock each year was the M N H R followed by the V W R . These two populations had been selected over several generations for increased body weights at 8 weeks of age. T h e ARB and L R B ranked intermediate in body weight while the A C R B and the N C R I R had the smallest body weights. T h u s , those lines which had a previous history of selection for increased body weight ( M N H R and VWR) demonstrated t h e effects of this prior selection b y being t h e heavier stocks in this experiment.
1431
1432
P . B . SlEGEL AND H . S. SlEGEL
T h e results of this experiment suggest t h a t randombreds may not be adequate environmental controls for populations for the characteristics measured. Differences between means of the two trials for the randombred populations are presented in Table 5. While admittedly the numbers of chicks per stock reported here were small, the range of differences between TABLE 5.—Differences1
trials were several times the standard errors of the particular traits. Furthermore, in some instances the signs were changed and corrections for the non-randombreds could be either plus or minus depending on the particular control used. T h u s , it appears t h a t further experimentation is necessary to determine if our results are indicative of what might occur with other traits and in other experimental situations before widespread recommendations are made for the use of randombreds as environmental controls for populations not derived from them. SUMMARY AND CONCLUSION
Comparisons were made for body weight, adrenal weight, and adrenal function among six stocks reared at two population densities in each of two years. Stocks consisted of three closed and three randombred populations. Floor space allowances were 464.5 and 929 cm 2 . N o significant differences between chicks maintained at the floor space allowances provided were observed at eight weeks of age—an age prior to the formation of peckrights. Sexual dimorphism with means for males being significantly higher t h a n those for females was noted for all weight characteristics and total adrenal cholesterol. No significant sexual dimorphism was observed either for adrenal cholesterol
between means of randombred populations cfd"
Trait Body wt. (g.) Right adr. wt. (mg.) Left adr. wt. (mg.) Total adr. wt. (mg.) Right adr. wt. (mg./lOO g.) Left adr. wt. (mg./lOO g.) Total adr. wt. (mg./lOO g.) Total adr. chol. (jug.) Adr. chol. (jug./mg.) 1
Trial 1—Trial 2 = difference.
LRB
ACRB
5.0 14.1 12.9 27.0 1.16 1.08 2.24 389.0 2.3
29.0 10.1 2.6 12.7 0.82 0.14 0.96 109.0 1.3
9 9 ARB 171.0 7.9 4.9 12.8 0.01 -0.26 -0.25 -108.0 -4.6
LRB
ACRB
ARB
53.0 8.1 -0.7 7.4 0.60 -0.33 0.27 195.0 5.4
-18.0 5.2 1.2 6.4 0.88 0.40 1.28 103.0 3.1
3.0 7.7 1.1 8.8 0.76 0.15 0.91 41.0 -0.2
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
meat-type birds b y Horton and McBride (1964). Interactions involving trials as a variable were not evaluated because analyses were made within trials, yet, it is of considerable interest to observe changes t h a t occurred in the means of randombred populations in two trials held at an interval of only one year. Recently there have been several reports on the variation of control populations of chickens (Kinney et al., 1968; Kinney and Lowe, 1968; Merritt, 1968). Under the assumption of genetic stability, randombred populations can be of considerable value as genetic controls and changes in their means can be used as corrections for environmental changes in selection experiments. T h e value of randombred populations would be further enhanced if they could be used as environmental controls for populations other t h a n those t h a t originated from the same gene pool as the random mating stocks.
ENDOCRINE RESPONSE AND STOCKS
REFERENCES Bronson, F. H., 1963. Density, subordination and social timidity in Peromyscus and C57BL/10J mice. Anim. Behav. 11: 475^77. Christian, J. J., 1950. The adreno-pituitary system and population cycles in mammals. J. Mamm. 31: 247-259. Christian, J. J., 1955. Effect of population size on weights of reproductive organs of white mice. Am. J. Physiol. 181: 477-480. Christian, J. J., and D. E. Davis, 1964. Endocrines, behavior and population. Science, 146: 15501560. Clarke, J. R., 1953. The effect of fighting on the adrenals, thymus and spleen of the vole {Microtus agresis). J. Endocrin. 9: 114-126. Davis, D. E., and J. J. Christian, 1957. Relation of adrenal weight to social rank of mice. Proc. Soc. Expt. Biol. Med. 94: 728-731. Dawson, J. S., and P. B. Siegel, 1967. Behavior patterns of chickens to ten weeks of age. Poultry Sci. 46: 615-622. Guhl, A. M., 1964. Psychophysiological interrelations in the social behavior of chickens. Psychol. Bui. 61:277-285. Guillemin, R., G. W. Clayton, H. S. Lipscomb and J. O. Smith, 1959. Fluometric measurement of rat plasma and adrenal corticosterone concentration. J. Lab. Clin. Med. 53: 830-832. Hess, C. W., 1962. Randombred populations of the Southern Regional Poultry Breeding Project.
World's Poultry Sci. J. 18: 147-152. Horton, I. F., and G. McBride, 1964. Genetic factors affecting sex dimorphism in body weight of meat chickens. Proc. Australian Poultry Cong. 77-81. Kinney, T. B., Jr., P. C. Lowe, B. B. Bohren and S. P. Wilson, 1968. Genetic and phenotypic variation in randombred White Leghorn controls over several generations. Poultry Sci. 47: 113— 123. Kinney, T. B., Jr., and P. C. Lowe, 1968. Genetic and phenotypic variation in regional red controls over nine years. Poultry Sci. 47: 1105-1110. Knobil, E., N. C. Hagney, E. I. Wilder and F. N. Breggs, 1954. Simplified method for determination of total adrenal cholesterol. Proc. Soc. Expt. Biol. Med. 87: 48-50. Lerner, I. M., 1954. Genetic Homeostasis. John Wiley & Sons, Inc. New York. Merritt, E. S., 1968. Genetic parameter estimates for growth and reproduction traits in a randombred control strain of meat type fowl. Poultry Sci. 47: 190-199. Siegel, H. S., 1960. Effect of population density on the pituitary-adrenal cortical axis of cockerels. Poultry Sci. 39: 500-510. Siegel, H. S., and P. B. Siegel, 1961. The relationship of social competition with endocrine weights and activity in male chickens. Anim. Behav. 9: 151-158. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term response and heritabilities. Poultry Sci. 41: 954-962. Thiessen, D. D., and D. A. Rogers, 1961. Population density and endocrine function. Psychol. Bui. 58: 441^51. Tindell, L. D., C. H. Moore, N. R. Gyles, W. A. Johnson, L. J. Dressen, G. A. Martin and P. B. Siegel, 1968. Genotype-environment interactions in broiler stocks of chickens. 2. Stock by location, stock by floor space and stock by trial interactions. Poultry Sci. 47: 721-733. Vandenbergh, J. G., 1960. Eosinophil response to aggressive behavior in CFW albino mice. Anim. Behav. 8: 13-18.
NOVEMBER 6-10, 1970. FIRST AMERICAN INSTITUTE OF BIOLOGICAL SCIENCES NATIONAL BIOLOGICAL CONGRESS, COBO HALL, DETROIT, MICHIGAN. FEBRUARY 12-15. FACT FINDING CONFERENCE, INSTITUTE OF AMERICAN POULTRY INDUSTRIES, MUNICIPAL AUDITORIUM, KANSAS CITY, MISSOURI.
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
concentrations per mg. of gland or for adrenal corticosterone. Differences among stocks were significant for all traits measured, except corticosterone, and rankings within sexes between years were consistent. Year to year fluctuations were as great for the randombreds as for the closed lines, however the direction of the change was not consistent for all stocks.
1433
grande for technical assistance during the course of this investigation. The work was supported by Institution Grant from the American Cancer Society. REFERENCES
lymphoid tissues and their dependence on protein synthesis. Fed. Proc. 23: 481. Hymer, W. C , and E. L. Kuff, 1965. Isolation of nuclei from mammalian tissues through the use of triton X-100. J. Histochem. Cytochem. 12: 359-363. Kirby, K. S., 1957. A new method for the isolation of deoxyribonucleic acids. Biochem. J. 66: 495504. Lang, N., and C. E. Sekeris, 1964. Zum Wirkungsmechanismus der Hormone: Z. Physiol. Chem. 339: 238-248. Nakagawa, S., and A. White, 1967. Response of rat thymic nuclear RNA polymerase to Cortisol injection. Endocrinol. 81: 861-870. Pratt, W. B., and L. Aronow, 1966. The effect of glucocorticoids on protein and nucleic acid synthesis in mouse fibroblasts growing in vitro. J. Biol. Chem. 241: 5244-5250. Scherrer, K., and J. E. Darnell, 1966. Sedimentation characteristics of rapidly labelled RNA from HeLa cells. Biochemical Biophysical Res. Comm. 7: 486^190. Stevens, W., C. Colessides and T. F. Dougherty, 1966. A time study on the effect of Cortisol on the incorporation of thymidine-2- u C into nucleic acids of mouse lymphatic tissue. Endocrinol. 78: 600-604. Weber, G. A., S. Srivastava and R. L. Singhal, 1965. Role of enzymes in homeostasis VLTI. Early effects of corticosteroid hormones in hepatic gluconeogenic enzymes, ribonucleic acid metabolism and amino acid level. J. Biol. Chem. 240: 750-756.
Endocrine Responses of Six Stocks of Chickens Reared at Different Population Densities P . B . SlEGEL AND H . S. SlEGEL 1 Virginia Polytechnic Institute, Blacksburg, Virginia 24061 (Received for publication March 8, 1969)
D
URING the past decade randombred populations have come into use as genetic and environmental controls in poultry experiments. In order for a 1 Present address: Southeast Poultry Research Laboratory, Athens, Ga.
population to be an adequate environmental control, its response to treatments should be consistent with that of other populations in the experiment. Homeostatic mechanisms (Lerner, 1954) may enable randombred populations to be better buffered to environmental changes
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
Bellamy, D., and R. Leonard, 1965. Effect of Cortisol on the growth of chicks. Gen. Comp. Endocrinol. 5:402^10. Bethell, J., H. Feigelson and P. Feigelson, 1965. The differential effects of glucocorticoids on tissue and plasma amino acid levels. Biochem. et Biophys. Acta, 104: 92-97. Bottoms, G., and D. D. Goetsch, 1967. Subcellular distribution of the (3H) corticosterone fraction in brain, thymus, heart, and liver of the rat. Proc. Soc. Exptl. Biol. Med. 124: 662-665. Bottoms, G. D., and D. D. Goetsch, 1968. Effects of corticosterone on oxidative metabolism in different tissues of the rat. Gen. Comp. Endocrinol. 10: 310-314. Burton, K., 1955. A study of the conditions and mechanism of the diphenylamine reaction for the colorimetric estimation of deoxyribonucleic acid. Biochem. J. 62: 315-323. Ceriotti, G., 1955. Determination of nucleic acids in animal tissues. J. Biol. Chem. 214: 59-70. Dougherty, T. F., and A. White, 1945. Functional alterations in lymphoid tissue induced by adrenal cortical secretion. Am. J. Anat. 77: 81-110. Feigelson, M., 1964. Cortisone induced alterations in purine and RNA metabolism in liver and
1425
1426
P. B. SIEGEL AND H. S. SIEGEL
Tests to study genotype-environment interactions of various stocks maintained at several locations at two population den-
sity levels were conducted as part of the Southern Regional Poultry Breeding Project (Tindell et al., 1968). Reported herein are differences in adrenal weights and functional activity among six of these stocks that were maintained at the two density levels at the Virginia station. MATERIALS AND METHODS
Experimental procedures were similar for the two trials which commenced May 24, 1962 and May 17, 1963. Eggs from each of ten stocks were sent by cooperators of the SRPB project to the Southern Regional Poultry Genetics Laboratory at Athens, Georgia, for incubation. Upon hatching, samples of chicks from each stock were shipped from that laboratory to ours where the experiments reported here were conducted. Endocrine data were obtained from six of the 10 stocks. Stocks. Lines sampled both years were: (1) North Carolina Rhode Island Red (NCRIR), (2) Mississippi New Hampshire Red (MNHR), (3) Louisiana Randombred (LRB), (4) Virginia High Weight White Plymouth Rock (VWR), (5) Athens-Canadian Randombred (ACRB), and (6) Athens Randombred (ARB). Descriptions of the first three populations were provided by their developers (W. L. Blow, L. J. Dressen, and W. A. Johnson). The NCRIR maintained at the Willard sub-station has been a closed population since at least 1946 with the exception of an introduction of some inbreds in 1956. The MNHR, a closed population since 1952, had undergone fairly intensive selection for body weight at 8 weeks of age since 1956. The LRB is a random mating population of about 25 males and 200 females established in 1954 from White and Dark Cornish, Buff Orpington, and White Leghorn populations. Siegel (1962) has described the VWR while Hess (1962) described the ACRB and ARB.
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
and might result in their being less sensitive to particular treatments than nonrandombred stocks. This lack of sensisitivity, in comparison to closed populations, might render randombreds less effective as environmental controls in certain situations. The influence of population density on certain endocrine responses has been demonstrated in several species (e.g. Christian, 1950, 1955; Siegel, 1960; Thiessen and Rogers, 1961; Christian and Davis, 1964). Differences have been shown in the endocrine response of laboratory and wild mice to population pressures (Christian, 1955) as well as species-density interactions (Bronson, 1963). Environmental improvements of poultry housing have resulted in increased numbers of chickens raised per unit area. Siegel (1960) found no consistent effects of population density on endocrine function in chickens to 11 weeks of age but afterwards increased density resulted in heavier adrenals and lower concentrations of adrenal cholesterol. Experiments with other species (Clarke, 1953; Davis and Christian, 1957; Vandenbergh, 1960) have suggested that the occurrence of agonistic behavior may be as important as increased population density in the manifestation of certain physiological changes. Although peckrights are not established in flocks of chickens until about 11 weeks of age (Guhl, 1964) agonistic behavior occurs prior to this age and peaks at about 8 weeks (Dawson and Siegel, 1967). Thus, the physiological effects of increased population densities may not be strongly manifested prior to this time. Also, chickens may be less responsive to such stimulation than mammals (Siegel and Siegel, 1961).
ENDOCRINE RESPONSE AND STOCKS
and corticosteroid concentrations (per gland and as fig. per mg. of adrenal). RESULTS AND DISCUSSION
Means and standard errors of the traits measured have been summarized within trials by stock and sex and are presented in Tables 1, 2, 3 and 4. Population density. No significant differences were found between birds maintained at the two floor space allowances for any of the traits measured with the exception of adjusted left adrenal weight in trial 1 where mean weights were 4.11 mg./lOO g. body weight at 464.5 cm.2 of floor space and 3.83 at the 929 cm.2 allowance. The lack of any consistent effect of population density on body weight under our conditions was consistent with that observed in the overall experiment by Tindell et al. (1968). The results for endocrine weights and adrenal cholesterol concentrations were consistent with those of Siegel (1960) who reported no effect to 11 weeks of age. They also support findings with other species (Clarke, 1953; Davis and Christian, 1957; Vandenbergh, 1960) in that the occurrence of agonistic behavior may be as important as population density in the manifestation of the physiological changes. Although the birds in our experiment did exhibit some agonistic behavior they were sacrificed during the early stages of the establishment of peckrights. Sex. Sexual dimorphism was observed for all weight characteristics and total adrenal cholesterol concentration with means for males being significantly higher than those for females. Sexual dimorphism was not found when adrenal cholesterol concentration was expressed at jug./mg. of gland or for corticosterone. Stocks. Significant differences were evi-
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
Management. Male and female chicks from the six stocks plus the other four stocks (not reported here) were intermingled in duplicate pens at each of two population densities. A total of 548 and 496 chicks were started in trials 1 and 2, respectively, with an equal number of birds started in each pen within each trial. Pens were modified so that half of the chicks were started at a floor space allowance of 464.5 cm2, and the other half at 929 cm2. An adjustment in floor space for mortality was made at 4 weeks of age. Chicks were placed m pens two days after hatching and remained there until the experiment was terminated 8 weeks later. A practical-type broiler diet was fed. Lighting was continuous and feeders consisted of three 36.8 cm. diameter tubes per pen and watering allowances were 1.3 cm. per chick started. Measurements. At 57 days of age 3 males and 3 females per treatment pen were selected for measurements of adrenal weight, adrenal cholesterol and corticosterone concentration. The procedure for both trials consisted of weighing chicks to the nearest gram and then sacrificing them by bleeding. Adrenal glands were removed, weighed separately to the nearest 0.1 mg., and immediately frozen for subsequent cholesterol and corticosterone determinations. The left gland was used for measurement of cholesterol (Knobil et al., 1954) and the right one for corticosterone (Guillemin et al., 1959). Statistical analyses were made on an intra-trial basis using a factorial analysis. Stocks, floor space levels, sex, and replicates were considered main effects and the appropriate interactions calculated, and means separated by Duncan's multiple range test. Analyses were made for body weight; left, right and total adrenal weight (unadjusted and adjusted to 100 g. of body weight); adrenal cholesterol;
1427
d"c? 9 9
&
R. adr. wt. (mg.)
L. adr. wt. (mg.)
T. adr. wt. (mg.)
R. adr. wt. (mg./lOO g.)
L. adr. wt. (mg./lOO g.)
T. adr. wt. (mg./lOO g.)
(2.1) (2.2)
82.9" 60.9"
7.63" (.26) 7.67" b (.34)
3.59" (.17) 3.58" b (.17)
4.04" (.14) 4.09»b (.24)
(1.4) (1.2)
(1.2) (1.7)
38.9" 28.4"
44.0» 32.5"
l,099" b (43) 801" (23)
NCRIR 1 (61) (44)
(3.9) (2.6)
(.33) (.18)
(.35) (.14)
8.25»b (.66) 6.87" (.23)
3.94" 3.25"
4.31" b 3.62"
118.2° (7.1) 81.6 b ° (4.4)
56.7° 38.4 b
61.5" (3.4) 43.2 b ° (2.7)
l^&P 1,186"
MNHR 2
(.46) (.14)
10.30° 8.47"
(.78) (.31)
4.90" (.35) 3.94" b (.22)
5.40° 4.53 b
115.8° (6.6) 82.9 b ° (4.2)
8.98" b (.27) 7.02" (.28)
4.28" b (.19) 3.34" b (.11)
4.70" bc (.18) 3.68" (.22)
104.8b° (3.4) 73.9b° (3.5)
50.2 b ° (2.6) 35.1" b (1.2)
(3.0) (2.3)
55.1° 38.4 b
54.61* (2.1) 38.8"°° (2.6)
l,182 b ° (50) l,052 b (27)
VWR 4
60.7^ (4.2) 44.5 b ° f2.3)
1,143"^ (32) 979» (34)
LRB 3
Stock
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
cfcf 9 9
Sex
Body wt. (g.)
Trait
TABLE 1.—Means and standard errors ( ) of body and gland weights by sex
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
9 9
9 9
L. adr. wt. (mg./lOO g.)
T. adr. wt. (mg./lOO g.)
3.98"" (.22) 3.65"" (.16) 4.02"° (.15) 3.26" (.15) 8.00"° (.39) 6.91" (.28)
4.24"" (.46) 3.93"" (.22) (.54) (.23)
3.82" 4.27" 8.06"° (.78) 8.20" (.40)
3.42" (.46) 3.62"" (.22) 3.32" (.54) 3.81"" (.23) 6.74" (.78) 7.44«" (.40)
3.84"" (.24) 3.34" (.25)
3.85"" (.16) 3.48" (.34)
7.69" 6.82"
(.34) (.43)
105.3° (5.7) 73.1"° (2.9)
88.8""° (4.4) 75.5"° (2.9)
97.1"° (4.4) 82.1° (2.9)
76.9" 57.6"
(2.7) (2.8)
52.4° (3.0) 38.6"° (1.6)
1,316° (32) l,058°d (26)
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
9 9
9 9
R. adr. wt. (mg./lOO g.)
T. adr. wt. (mg.)
46.6"° (2.6) 36.4"° (2.0)
1,138" (48) 926"" (35)
VWR 4
52.9° (2.8) 34.5"" (1.8)
(2.9) (2.0)
(48) (35)
49.3"° (2.6) 40.2° (2.0)
l,436 d 1,103d
LRB 3
42.2"" (2.5) 39.1"° (1.3)
38.6" 29.6"
cfb 1 9 9
L. adr. wt. (mg.)
(1-9) (1.7)
(20) (33)
MNHR 2
Stock
47.8"° (2.5) 41.9° (1.3)
38.3" 28.0"
1,055" 856"
NCRIR 1
cfcf 9 9
9 9
Sex
R. adr. wt. (mg.)
Body wt. (g.)
Trait
1
TABLE 2.—Means and standard errors ( ) of body and gland weights by sex a
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
3.33" 2.58"
d'd 1 9 9
(.31) (.25)
(.13) (.07) 2.59" 3.42"
1.59" 1.42" (.19) (.30)
2.13" 2.99"
(.21) (.20)
2.76" 3.02"
(.27) (.36)
(.13) (.13)
1.49" 1.15"
1.28" 1.32"
(.12) (.09)
(.14) (.11)
20.9"" (1.2) 21.7" (1.0)
23.6"" (1.0) 21.6" (1.2)
1,025"" (43) 764"" (49)
1,282"" (60) 835" (80)
(1.6) (1.0)
(155) (50)
VWR 4
LRB 3
Stock
9 9
Adr. cholesterol. (Total Mg.)
(82) (51)
(1.4) (1.6)
(.10) (.07)
(.28) (.32)
647" 520"
17.0" 17.7"
1.32" 1.21"
3.84" 4.04"
NCRIR 1
3.24" 3.50"
(.27) (.54)
3.58" 4.20"
(.21) (.19)
3.09" 3.76"
1.68" 1.35"
(.12) (.16)
1.64" 1.47"
(.11) (.11)
1.52" 1.49"
(.23) (.23)
(.13) t.ll)
(1.6) (2.2)
973"" (86) 810" (108)
VWR 4
18.6" 22.9"
(2.3) (2.2)
30.6" 30.0"
893"" (110) 640"" (103)
LRB 3
21.3"" (2.3) 16.2" (2.2)
(110) (103)
1,433d 1,260=
MNHR 2
Stock
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
0«. %)
9 9
9 9
Adr. corticos. (Total Mg.)
Adr. corticos.
9 9
(/Ltg./mg.)
Adr. cholesterol
Sex
Trait
TABLE 4.—Means and standard errors ( ) of adrenal cholesterol and corticosterone b
Any two means on a horizontal with the same superscript are not significantly different (P<.05).
0«. %)
Adr. corticos.
1.46" .82"
9 9
Adr. corticos. (Total /ig.)
24.8" 43.2"
22.8«b (3.3) 20.7" (1.2)
9 9
Adr. cholesterol (Mg-/mg.)
1,428" 879"
MNHR 2
(115) (28)
872" 578"
NCRIR 1
9 9
Sex
(Total „g.)
Adr. cholesterol
Trait
TABLE 3.—Means and standard errors ( ) of adrenal cholesterol and corticosterone b
http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
E N D O C R I N E R E S P O N S E AND STOCKS
Adrenal weight. There was a positive association between adrenal weight and body weight in the relative rankings of the stocks. T h e N C R I R consistently had the lightest adrenal glands followed by the A C R B . Fluctuations in rankings for adrenal weights varied among the other four stocks depending on the sex and trial. R a n k correlations between mean adrenal weights unadjusted for body weight and those expressed as mg./lOO g. of body weight were, in most instances, of a low magnitude. Using total adrenal weight as a n example, the rank correlations between adjusted and unadjusted values were .20 a n d .32 for males and females, respectively, in trial 1 and —.14 for males and .72 for females in trial 2. T h u s , comparisons among stocks for adrenal weight should be more meaningful when expressed as per 100 g. of body weight. Significant differences were found among stocks for adrenal weight expressed as mg./lOO g. of body weight. Weights for the three randombred populations appeared to be heavier than those for the selected ones, although differences were not always significant. Among the selected populations there were no significant dif-
ferences between the N C R I R and the VWR. Means for the M N H R were of a similar magnitude to the other selected populations, with the exception of the males in trial 2 where the weights for the left and both glands were significantly lower. Adrenal cholesterol and corticosterone. Cholesterol content of the left adrenal gland expressed either as total or fig./ mg. of gland was highest in the M N H R . Conversely, the N C R I R was consistently among the lower ranking stocks for this characteristic. T h e other nonrandombred population, the V W R , ranked intermediate to the M N H R and the N C R I R . No significant difference existed in either trial among the randombred females for cholesterol concentration. Among males, levels were significantly higher for the A R B than for the A C R B in three of four comparisons, while means for the L R B were intermediate to the other randombreds. No significant differences were found among stocks or between floor space treatments for corticosterone. Interactions. T h e interaction, sex-floor space, was not significant for any trait measured in either trial. Further, in only 1 of the 22 analyses of variance made was the stock-floor space interaction significant. The exception, adjusted adrenal weight in trial 2, was probably a chance occurrence. These results suggest t h a t both sexes and all stocks responded in a similar manner to 8 weeks of age at both population densities. Although significant stock-sex interactions were not observed in trial 1, several were observed in trial 2. These were for body weight, left adrenal weight (adjusted and unadjusted for body weight) and for total adrenal weight adjusted for body weight. Stock-sex interactions m a y be expected when the sexual dimorphism is not the same for all stocks as shown in
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
d e n t among stocks for all characteristics within each trial, with the exception of corticosterone. Ranking of stocks within sexes between years were consistent. Body weight. T h e heaviest stock each year was the M N H R followed by the V W R . These two populations had been selected over several generations for increased body weights at 8 weeks of age. T h e ARB and L R B ranked intermediate in body weight while the A C R B and the N C R I R had the smallest body weights. T h u s , those lines which had a previous history of selection for increased body weight ( M N H R and VWR) demonstrated t h e effects of this prior selection b y being t h e heavier stocks in this experiment.
1431
1432
P . B . SlEGEL AND H . S. SlEGEL
T h e results of this experiment suggest t h a t randombreds may not be adequate environmental controls for populations for the characteristics measured. Differences between means of the two trials for the randombred populations are presented in Table 5. While admittedly the numbers of chicks per stock reported here were small, the range of differences between TABLE 5.—Differences1
trials were several times the standard errors of the particular traits. Furthermore, in some instances the signs were changed and corrections for the non-randombreds could be either plus or minus depending on the particular control used. T h u s , it appears t h a t further experimentation is necessary to determine if our results are indicative of what might occur with other traits and in other experimental situations before widespread recommendations are made for the use of randombreds as environmental controls for populations not derived from them. SUMMARY AND CONCLUSION
Comparisons were made for body weight, adrenal weight, and adrenal function among six stocks reared at two population densities in each of two years. Stocks consisted of three closed and three randombred populations. Floor space allowances were 464.5 and 929 cm 2 . N o significant differences between chicks maintained at the floor space allowances provided were observed at eight weeks of age—an age prior to the formation of peckrights. Sexual dimorphism with means for males being significantly higher t h a n those for females was noted for all weight characteristics and total adrenal cholesterol. No significant sexual dimorphism was observed either for adrenal cholesterol
between means of randombred populations cfd"
Trait Body wt. (g.) Right adr. wt. (mg.) Left adr. wt. (mg.) Total adr. wt. (mg.) Right adr. wt. (mg./lOO g.) Left adr. wt. (mg./lOO g.) Total adr. wt. (mg./lOO g.) Total adr. chol. (jug.) Adr. chol. (jug./mg.) 1
Trial 1—Trial 2 = difference.
LRB
ACRB
5.0 14.1 12.9 27.0 1.16 1.08 2.24 389.0 2.3
29.0 10.1 2.6 12.7 0.82 0.14 0.96 109.0 1.3
9 9 ARB 171.0 7.9 4.9 12.8 0.01 -0.26 -0.25 -108.0 -4.6
LRB
ACRB
ARB
53.0 8.1 -0.7 7.4 0.60 -0.33 0.27 195.0 5.4
-18.0 5.2 1.2 6.4 0.88 0.40 1.28 103.0 3.1
3.0 7.7 1.1 8.8 0.76 0.15 0.91 41.0 -0.2
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
meat-type birds b y Horton and McBride (1964). Interactions involving trials as a variable were not evaluated because analyses were made within trials, yet, it is of considerable interest to observe changes t h a t occurred in the means of randombred populations in two trials held at an interval of only one year. Recently there have been several reports on the variation of control populations of chickens (Kinney et al., 1968; Kinney and Lowe, 1968; Merritt, 1968). Under the assumption of genetic stability, randombred populations can be of considerable value as genetic controls and changes in their means can be used as corrections for environmental changes in selection experiments. T h e value of randombred populations would be further enhanced if they could be used as environmental controls for populations other t h a n those t h a t originated from the same gene pool as the random mating stocks.
ENDOCRINE RESPONSE AND STOCKS
REFERENCES Bronson, F. H., 1963. Density, subordination and social timidity in Peromyscus and C57BL/10J mice. Anim. Behav. 11: 475^77. Christian, J. J., 1950. The adreno-pituitary system and population cycles in mammals. J. Mamm. 31: 247-259. Christian, J. J., 1955. Effect of population size on weights of reproductive organs of white mice. Am. J. Physiol. 181: 477-480. Christian, J. J., and D. E. Davis, 1964. Endocrines, behavior and population. Science, 146: 15501560. Clarke, J. R., 1953. The effect of fighting on the adrenals, thymus and spleen of the vole {Microtus agresis). J. Endocrin. 9: 114-126. Davis, D. E., and J. J. Christian, 1957. Relation of adrenal weight to social rank of mice. Proc. Soc. Expt. Biol. Med. 94: 728-731. Dawson, J. S., and P. B. Siegel, 1967. Behavior patterns of chickens to ten weeks of age. Poultry Sci. 46: 615-622. Guhl, A. M., 1964. Psychophysiological interrelations in the social behavior of chickens. Psychol. Bui. 61:277-285. Guillemin, R., G. W. Clayton, H. S. Lipscomb and J. O. Smith, 1959. Fluometric measurement of rat plasma and adrenal corticosterone concentration. J. Lab. Clin. Med. 53: 830-832. Hess, C. W., 1962. Randombred populations of the Southern Regional Poultry Breeding Project.
World's Poultry Sci. J. 18: 147-152. Horton, I. F., and G. McBride, 1964. Genetic factors affecting sex dimorphism in body weight of meat chickens. Proc. Australian Poultry Cong. 77-81. Kinney, T. B., Jr., P. C. Lowe, B. B. Bohren and S. P. Wilson, 1968. Genetic and phenotypic variation in randombred White Leghorn controls over several generations. Poultry Sci. 47: 113— 123. Kinney, T. B., Jr., and P. C. Lowe, 1968. Genetic and phenotypic variation in regional red controls over nine years. Poultry Sci. 47: 1105-1110. Knobil, E., N. C. Hagney, E. I. Wilder and F. N. Breggs, 1954. Simplified method for determination of total adrenal cholesterol. Proc. Soc. Expt. Biol. Med. 87: 48-50. Lerner, I. M., 1954. Genetic Homeostasis. John Wiley & Sons, Inc. New York. Merritt, E. S., 1968. Genetic parameter estimates for growth and reproduction traits in a randombred control strain of meat type fowl. Poultry Sci. 47: 190-199. Siegel, H. S., 1960. Effect of population density on the pituitary-adrenal cortical axis of cockerels. Poultry Sci. 39: 500-510. Siegel, H. S., and P. B. Siegel, 1961. The relationship of social competition with endocrine weights and activity in male chickens. Anim. Behav. 9: 151-158. Siegel, P. B., 1962. Selection for body weight at eight weeks of age. 1. Short term response and heritabilities. Poultry Sci. 41: 954-962. Thiessen, D. D., and D. A. Rogers, 1961. Population density and endocrine function. Psychol. Bui. 58: 441^51. Tindell, L. D., C. H. Moore, N. R. Gyles, W. A. Johnson, L. J. Dressen, G. A. Martin and P. B. Siegel, 1968. Genotype-environment interactions in broiler stocks of chickens. 2. Stock by location, stock by floor space and stock by trial interactions. Poultry Sci. 47: 721-733. Vandenbergh, J. G., 1960. Eosinophil response to aggressive behavior in CFW albino mice. Anim. Behav. 8: 13-18.
NOVEMBER 6-10, 1970. FIRST AMERICAN INSTITUTE OF BIOLOGICAL SCIENCES NATIONAL BIOLOGICAL CONGRESS, COBO HALL, DETROIT, MICHIGAN. FEBRUARY 12-15. FACT FINDING CONFERENCE, INSTITUTE OF AMERICAN POULTRY INDUSTRIES, MUNICIPAL AUDITORIUM, KANSAS CITY, MISSOURI.
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 11, 2014
concentrations per mg. of gland or for adrenal corticosterone. Differences among stocks were significant for all traits measured, except corticosterone, and rankings within sexes between years were consistent. Year to year fluctuations were as great for the randombreds as for the closed lines, however the direction of the change was not consistent for all stocks.
1433