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Changes in Reproductive Traits Associated with Selection for Packed Erythrocyte Volume in Japanese Quail
Changes in Reproductive Traits Associated with Selection for Packed Erythrocyte Volume in Japanese Quail K . W . WASHBURN AND F . K . R. STINO
Department of Poultry Science, University of Georgia, Athens, Georgia 30602 (Received for publication January 6, 1973)
POULTRY SCIENCE: 2147-2152, 1973
I
F a true biological association exists between two traits and selection pressure is applied to one, the other may also change if the environment allows its expression. This association between selected and non-selected traits is usually considered a result of linked polygenic blocks or to pleiotropy. Polygenic blocks, if they have relatively loose linkage, may cause only a transient association (Lerner, 1958). However, the genes may be so closely linked that unless an extremely large number of individuals can be obtained no recombinant types will be observed and the phenotypic effect of the linked genes will appear to be the effect of a pleiotropic gene. A pleiotropic effect may result from the use of the basic gene product for different reactions. Thus, if the phenotypic selection pressure changes the genes present both traits will be affected. Associated changes in traits may also be due to physiological changes brought about by the primary effect of a gene. A classical example is that of sickle cell anemia which is the result of a single point mutation in the gene responsible for a hemoglobin chain (Ingram, 1963). The abnormal hemoglobin structure causes an abnormally shaped erythrocyte resulting in a multitude of physiological effects. In addition to the associated changes of traits due to the effects
of linkage and pleiotropy a disruption of the genetic balance of a population by selection for one trait might cause changes in other traits. Thus, associated changes in traits under selection pressure may be due to a number of basic causes. Seldom is the necessary fine structure analysis possible to completely differentiate between linkage and pleiotropy or to determine cause and effect relationships. Regardless of the cause of the association between traits the net result in a selection program is the same. Stino and Washburn (1972) reported the effects of selection for divergence of 15-day packed erythrocyte volume (PCV) in Japanese quail. In four generations of selection they separated a high PCV line from a low PCV line by a factor of 29 percent using an adequate Fe-Cu diet and by 18 percent using a Fe-Cu deficient (stress) diet. During the four generations of selection differences developed between the lines in egg production rate, fertility and hatchability. The present study discusses the changes in unselected traits which occurred in the selection for PCV. MATERIALS AND METHODS Data were obtained from the four lines of Japanese quail (Stino and Washburn, 1972)
2147
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ABSTRACT During the separation of lines for high and low packed erythrocyte volume (PCV) of Japanese quail fed Fe, Cu adequate or Fe, Cu deficient diets, differences in egg production rate, fertility and hatchability developed but there were no changes noted in body weight. Lowered egg production appeared to be associated with selection for lowered PCV, but was not a direct effect of PCV level. Concomitant changes in fertility and hatchability were noted under both the Fe-Cu adequate and Fe-Cu deficient dietary environments. A decreased fertility and hatchability of low PCV lines compared to their respective high lines was observed. Reciprocal crosses of the high and low PCV lines indicated heterosis for body weight and hatchability, and apparent paternal effect for body weight and an apparent maternal effect for hatchability.
2148
K. W. WASHBURN AND F. K. R. STINO
RESULTS AND DISCUSSION The changes in the selected trait (PCV) and non-selected traits (body weight, egg production, fertility and hatchability) are presented in Fig. 1. These comparisons are based
« 4
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a.
o
•
^
- I 4
V
6 1
1
1
1
1
P
S|
s2
S3
S4
P
Sj
S2 S3
P
S,
S2
S4
The unselected characteristics reported here, and how and when they were measured are:
1) Fifteen-day body weight—all quail were individually weighed in grams at 15 days of age. 2) Egg production—hen-day egg production was measured for 100 days from the age at 50 percent production for the female parents and their reserves (number of reserves were 50 percent of that of the parents of each line). 3) Fertility—fertility was considered percentage fertile eggs of total eggs. All unhatched eggs were opened and macroscopically examined to determine the fertility. In each generation only males which had previously showed fertility were placed in the breeding pens. 4) Hatchability—hatchability was considered as the percentage hatched quail of total fertile eggs. Hatchability was not considered when the fertility of female was zero. 5) Temperament—temperament was visually observed, but was not quantitatively measured.
---• o --o
P
S3 S 4
LA HS IS
S,
S2
S3
S4
GENERATION
FIG. 1. Changes in selected trait (packed erythrocyte volume—PCV) and non-selected traits of body weight, egg production, fertility and hatchability, presented as deviation of randombred control. H = high line; L = low line A = Fe, Cu adequate (non-stress) diet S = Fe, Cu deficient (stress) diet HA = high PCV line selected on Fe, Cu adequate diet LA = low PCV line selected on Fe, Cu adequate diet HS = high PCV line selected on Fe, Cu deficient (stress) diet LS = low PCV line selected on Fe, Cu deficient (stress) diet
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which had been mass-selected in divergent directions for 15-day PCV under two nutritional environments. The two nutritional environments were an Fe-Cu adequate, turkey starter diet and an Fe-Cu deficient, skim milk diet. After four generations of selection reciprocal crosses between the various lines were made. Eggs from the randombred quail population maintained at the Southern Regional Poultry Genetics Laboratory as 120 paired matings were obtained each generation, hatched and reared under both the Fe-Cu adequate and the Fe-Cu deficient dietary regimes to serve as controls. Selection procedures and management practices were presented in detail by Stino (1970).
2149
SELECTION FOR PACKED CELL VOLUME
on deviations from controls (sexes combined) of the high and low PCV lines selected on Fe, Cu adequate diet (HA, LA) and high and low PCV lines selected on Fe, Cu deficient (stress) diet (HS, LS). The randombred controls were reared intermingled in each of the selection environments.
TABLE 1.—Phenotypic correlations of unselected traits with 15-day PCV of high and low lines under adequate Fe-Cu and Fe-Cu deficient (stress) diets. Fe-Cu adequate diet HA 2
Population
P, 2 week body wt. - . 1 4 Egg prod. .31 .05 % Fert. % Hatch. .10
LA
s,
S2
s3
--.06 .36 .05 .08
.03 -.01 .13 .01
-.08 .40 .19 .15
X1
P,
s,
S2
s3
-.06 + .27 + .10 + .08
0.14** -.25 -.14 .01
.02 -.36 -.01 -.03
.03 -.09 -.13 .05
.14 -.40 .34 .40*
X + .01 -.28 + .01 + .10
Fe-Cu deficient (stress) diet Population
LS
HS Pi
s,
2 week body wt. .16** .13 Egg prod. .15 --.30 % Fert. -.07 .12 % Hatch. - . 1 5 .12
s2
s3
.14*
.38**
.06 -.04 -.01
.07 -.01 .13
X + .20 0.0 0.0 + .02
P, .16** -.35 .10 -.19
s, -.02 -.44 -.05 .17
s2
s3
X
.14*
.26**
+ .13
-.22 .22 .08
' X = arithmetic mean for all values H = high PCV; L = low PCV; A = adequate Fe, Cu; S = deficient Fe, Cu. "Correlation significant at P s .05. 'Correlation significant at P s .01. 2
-.40 .06 .23
-.35 + .08 + .07
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Body Weight. Differences in 15-day body weight between the high and low PCV lines (within a selection regime) were not significant in any generation or when analyzed over generations. In the S 3 generation the body weight of the controls responded somewhat differently to the environments which resulted in all the selected lines appearing to be heavier in body weight. The mean within-line phenotypic correlations for the four generations between 2 week body weight and PCV (Table 1) were -0.06 for the HA, +0.01 for the LA, +0.20 for the HS and +0.13 for the LS line. The correlations were sometimes significant within a generation. However, the low magnitude of the correlation and comparisons of the
relatively small changes in body weight of the HS line (which had the highest correlation) and other lines which had a lower correlation (example—HA) with randombreds indicate the significance is not a measure of consistent response. Washburn and Edwards (1970) reported a relationship between body weight and PCV depression of chicks fed an Fe, Cu deficient diet. However, in this selection experiment using Japanese quail there appears to be no trend of association of PCV with body weight. Some heterosis for body weight was noted in the S 4 reciprocal cross progeny (Table 2). The crossline progeny were significantly heavier than selected line progeny except for the LA x HA crosses. The differences between the reciprocal crosses were significant (P < .01), in favor of the high PCV male x low PCV male cross (HA x LA). This closer resemblance between progeny average and their sire was reported earlier by Olsen and Knox (1940) in egg weight of chickens, Siegel (1963) in body weight of chickens and Stino and Washburn (1972) in PCV of quails.
2150
K. W. WASHBURN AND F. K. R. STINO
TABLE 2.—Means of 15-day body weight of S4 crosses and fertility and hatchability of their parents
Crosses
HA x HA
1
Fe-Cu adequate diet LA x HA HA x LA LA x LA
RBA
Arithmetic mean
Trait: 2 week body weight
38.4"
41.0C
35.6a
37.68b
36.9
Fertility X Hatch 1-Hatch 2
70.9 75.6 66.1
85.7 88.7 82.6
73.1 72.1 74.0
71.2 67.6 74.7
77.7 82.2 73.2
71.7
Hatchability X 3 Hatch 1-Hatch 2
70.3 68.6 72.0
66.6 70.0 63.2
59.3 68.5 50.0
46.2 40.0 52.3
61.2 71.1 51.2
58.3
3
HS x HS'
LS x HS
HS x LS
LS x LS
RBS
Arith^ metic mean
27.3 ab2
2 0 Qcd
31.2"
24.8"
28.7 bc
26.1
Fertility X Hatch 1-Hatch 2
86.6 92.6 80.6
81.9 79.9 83.9
82.1 85.5 78.6
76.6 81.3 71.8
88.6 91.9 85.3
81.6
Hatchability X 3 Hatch 1-Hatch 2
68.3 72.2 64.4
80.0 81.3 78.7
70.5 67.3 73.6
54.8 56.3 53.2
68.1 73.5 62.5
61.1
Fe-Cu deficient (stress) diet Crosses Trait: 2 week body weight 3
'H = High PCV line, L = Low PCV line; sires listed first in denoting mating. A = Fe-Cu adequate; S 2= Fe-Cu deficient Values with different superscript within diets are significantly different (P s .01) using Duncan (1955) multiple range test. 3 Average of two replicates (500 eggs)
Egg Production. The egg production of all selected lines was decreased in the S, generation (Fig. 1). That of the low PCV lines (both on the adequate and stress diets) remained at a level significantly (P =£ .05) lower than their controls for the duration of the selection. However, those of the high line returned to control levels in subsequent generations and differences between either of the high PCV lines and randombreds were not significant. This depression in egg production in the S l generation cannot be attributed to inbreeding depression since it was slight for that generation. These results indicate an association of egg production with selection for PCV, with lowered PCV being associated with lowered egg production. PCV values higher than that normally found may not affect egg production. This relationship of lowered PCV and
lowered egg production appears not to be a direct effect of PCV. The phenotypic correlations between PCV and body weights within lines were consistently negative for both low lines (-0.28 for LA; -0.35 for LS) which indicates that as the PCV is decreased by selection the mean egg production should increase. If the progress in decreasing the PCV of the two low lines is examined (Fig. 1), considerably more progress was made in selection for the low PCV line in the adequate Fe-Cu environment (non-stress). Little progress was made in selection for low PCV on the Fe-Cu deficient environment although there was more selection pressure on this line than on the adequate low line. However, the egg production of both low lines was depressed. These observations would indicate that the selection pressure for genes contributing to reduced PCV was bringing
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38.1" 2
SELECTION FOR PACKED CELL VOLUME
Fertility. Concomitant changes in fertility of total eggs were noted when divergent selection was made for 15-day PCV under both the Fe-Cu adequate and Fe-Cu deficient dietary environments (Fig. 1). Comparisons between the high and low lines within a selection environment indicate fertility of the high PCV adequate line was higher than the respective low PCV lines for all generations. Although differences between these lines were slight for the S 3 and S 4 generations, the low PCVadequate Fe, Cu line was consistently depressed (significant at P s .05) in fertility compared to the randombred control. When selection was practiced under the Fe-Cu deficient dietary conditions the same trend of decreased fertility of the low PCV line compared to their respective high line was observed. However, fertility was not lower when compared to the randombred control except for the S 3 and S 4 generation. The mean phenotypic correlations of PCV with fertility (Table 1) were +0.10, -0.01, 0.0 and +0.08 for the HA, LA, HS and LS lines, respectively, which would indicate that changes in PCV per se were not the reason for the reduced fertility. If the comparative changes in fertility in the lines over generations are compared (Fig. 1), it is seen that the high and low lines first diverged and then in subsequent generations converged al-
though differences in PCV were greatest in the S4 generations. Under the Fe-Cu adequate feeding regime, reciprocal crosses of the selected lines had higher average fertility than either selected lines (Table 2). The low (LA) male x high (HA) female cross showed more heterosis than the reciprocal cross (HA male x LA female). Under the Fe-Cu stress conditions the reciprocal crosses were intermediate to the selected lines. Hatchability. Individual selection in divergent directions for 15-day PCV resulted in associated changes in hatchability of fertile eggs (Fig. 1). Under the Fe-Cu adequate diet conditions, the high PCV line had significantly (P s .01) higher hatchability than the low PCV line with the randombred being intermediate. Under the Fe-Cu stress diet condition, this trend was apparent after the S, generation. This may be due to the limited progress made in selecting for PCV in the downward direction under the Fe-Cu stress condition until the S 2 generation (Stino, 1971). A possible explanation for this association is that the low hatchability of the low PCV line was due to the anoxia of the low PCV line embryos. The developing embryos require a certain amount of oxygen carrying capacity of their blood. If this requirement is not satisfied, due to severe inherited anemia in this case, the embryo will not be able to develop properly and consequently may die. This also seems reasonable since the hatchability of the low stress line was affected only when progress was made in the downward direction. Hatchability of fertile eggs of S 3 parents in each of two hatches was higher in the high PCV lines than in the low PCV line with the randombred intermediate under the Fe-Cu adequate feeding regime (Table 2). Reciprocal crosses of S 3 parents were intermediate between the selected lines. However, a definite maternal effect was observed in
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into play genes that had a deleterious effect on egg production. Since the PCV of the population on the Fe-Cu deficient diet was already low, natural selection may have been more intense against further genetic depression of PCV, but not against subsequent egg production which was not affected by the 5-15 day stress environment conditions. The depression in egg production observed in all selected lines after one generation may have been due to disruption of the genetic balance in the randombred. This decrease in production was restored in subsequent generations.
2151
2152
K. W. WASHBURN AND F. K. R. STINO
Temperament. Although temperament was not quantitated, it was visually obvious that both high PCV lines were more nervous than either low PCV line. This observation was most noticeable for the S 3 and S 4 generations. When transferring the breeders a number of high-line individuals were observed to fly against the top of the battery until they collapsed and died. The loss of birds in this way was restricted to the two high PCV lines and was not observed in either the low-lines or the randombreds. This nervousness of the high PCV lines could be due to increased blood pressure (Weiburt and Schlager, 1968) or adrenal or thyroid activity or a combination of these factors. Washburn and Guill (1972) reported that the PCV of White Leghorns was higher than that of heavy breeds, indicating the possibility of associating the known nervousness of Leghorns with higher PCV. If the changes in egg production, fertility and hatchability were due to a direct association with PCV, then differences in PCV and these traits in the original population should be associated. Additional evidence is presented in Table 3 that the changes in egg production, fertility and hatchability that appeared to be associated with extremes of
TABLE 3.—Phenotypic correlations between PCV, egg production rate, fertility and hatchability of randombred Coturnix quail.
Non-selected trait Production Fertility Hatchability
Correlation cJPCV 9 PCV Combined sexes .03 -.07 .003 .06 -.07 .2 .03 -.05 .1
PCV is not a direct effect of PCV. When the production, fertility, hatchability and the packed cell volume of the original population was compared there was no significant correlation. REFERENCES Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Ingram, V. M., 1963. The Hemoglobins in Genetics and Evolution. Columbia University Press, New York, N.Y. Lerner, M. I., 1958. The Genetic Basis of Selection. John Wiley and Sons, Inc. New York, N.Y. Olsen, M. W., and C. W. Knox, 1940. Breeding for egg weight and related characters. Poultry Sci. 19: 254-257. Siegel, P. B., 1963. Selection for breast angle at eight weeks of age. 2. Correlated responses of feathering, body weights and reproductive characteristics. Poultry Sci. 42: 437-449. Stino, F. K. R., 1971. Divergent selection for PCV in the Japanese quail under two environments. Ph.D. Thesis, University of Georgia. Stino, F. K. R., and K. W. Washburn, 1972. Divergent selection for two-week packed erythrocyte volume under two nutritional environments in the Japanese quail. Genetics (In Press). Washburn, K. W., and H. M. Edwards, 1970. Variability in hematological response of chicks fed an iron-copper deficient diet. Poultry Sci. 49: 122-127. Washburn, K. W., and R. A. Guill, 1972. Comparison of hematology between Leghorn-type and heavytype egg production stocks: possible association of hematology and Columbian restriction of plumage. Poultry Sci. 52: 946-950. Weiburt, R. S., andG. Schlager, 1968. A genetic study of blood pressure, hematocrit and plasma cholesterol in aged mice. Life Sciences, Part 2, 7: 1111-1119.
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both hatches, with the low PCV male x high PCV female cross having higher hatchability. The randombred was intermediate and near the mean of the high PCV male x low PCV female cross. Under the Fe-Cu stress feeding conditions, the reciprocal crosses showed heterosis over both selected lines with the randombred hatchability being similar to that of the high PCV line (Table 2). A maternal effect was also present with heterosis, where the high PCV line females showed higher hatchability than the low PCV line females in both hatches.
Department of Poultry Science, University of Georgia, Athens, Georgia 30602 (Received for publication January 6, 1973)
POULTRY SCIENCE: 2147-2152, 1973
I
F a true biological association exists between two traits and selection pressure is applied to one, the other may also change if the environment allows its expression. This association between selected and non-selected traits is usually considered a result of linked polygenic blocks or to pleiotropy. Polygenic blocks, if they have relatively loose linkage, may cause only a transient association (Lerner, 1958). However, the genes may be so closely linked that unless an extremely large number of individuals can be obtained no recombinant types will be observed and the phenotypic effect of the linked genes will appear to be the effect of a pleiotropic gene. A pleiotropic effect may result from the use of the basic gene product for different reactions. Thus, if the phenotypic selection pressure changes the genes present both traits will be affected. Associated changes in traits may also be due to physiological changes brought about by the primary effect of a gene. A classical example is that of sickle cell anemia which is the result of a single point mutation in the gene responsible for a hemoglobin chain (Ingram, 1963). The abnormal hemoglobin structure causes an abnormally shaped erythrocyte resulting in a multitude of physiological effects. In addition to the associated changes of traits due to the effects
of linkage and pleiotropy a disruption of the genetic balance of a population by selection for one trait might cause changes in other traits. Thus, associated changes in traits under selection pressure may be due to a number of basic causes. Seldom is the necessary fine structure analysis possible to completely differentiate between linkage and pleiotropy or to determine cause and effect relationships. Regardless of the cause of the association between traits the net result in a selection program is the same. Stino and Washburn (1972) reported the effects of selection for divergence of 15-day packed erythrocyte volume (PCV) in Japanese quail. In four generations of selection they separated a high PCV line from a low PCV line by a factor of 29 percent using an adequate Fe-Cu diet and by 18 percent using a Fe-Cu deficient (stress) diet. During the four generations of selection differences developed between the lines in egg production rate, fertility and hatchability. The present study discusses the changes in unselected traits which occurred in the selection for PCV. MATERIALS AND METHODS Data were obtained from the four lines of Japanese quail (Stino and Washburn, 1972)
2147
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 20, 2015
ABSTRACT During the separation of lines for high and low packed erythrocyte volume (PCV) of Japanese quail fed Fe, Cu adequate or Fe, Cu deficient diets, differences in egg production rate, fertility and hatchability developed but there were no changes noted in body weight. Lowered egg production appeared to be associated with selection for lowered PCV, but was not a direct effect of PCV level. Concomitant changes in fertility and hatchability were noted under both the Fe-Cu adequate and Fe-Cu deficient dietary environments. A decreased fertility and hatchability of low PCV lines compared to their respective high lines was observed. Reciprocal crosses of the high and low PCV lines indicated heterosis for body weight and hatchability, and apparent paternal effect for body weight and an apparent maternal effect for hatchability.
2148
K. W. WASHBURN AND F. K. R. STINO
RESULTS AND DISCUSSION The changes in the selected trait (PCV) and non-selected traits (body weight, egg production, fertility and hatchability) are presented in Fig. 1. These comparisons are based
« 4
> u
a.
o
•
^
- I 4
V
6 1
1
1
1
1
P
S|
s2
S3
S4
P
Sj
S2 S3
P
S,
S2
S4
The unselected characteristics reported here, and how and when they were measured are:
1) Fifteen-day body weight—all quail were individually weighed in grams at 15 days of age. 2) Egg production—hen-day egg production was measured for 100 days from the age at 50 percent production for the female parents and their reserves (number of reserves were 50 percent of that of the parents of each line). 3) Fertility—fertility was considered percentage fertile eggs of total eggs. All unhatched eggs were opened and macroscopically examined to determine the fertility. In each generation only males which had previously showed fertility were placed in the breeding pens. 4) Hatchability—hatchability was considered as the percentage hatched quail of total fertile eggs. Hatchability was not considered when the fertility of female was zero. 5) Temperament—temperament was visually observed, but was not quantitatively measured.
---• o --o
P
S3 S 4
LA HS IS
S,
S2
S3
S4
GENERATION
FIG. 1. Changes in selected trait (packed erythrocyte volume—PCV) and non-selected traits of body weight, egg production, fertility and hatchability, presented as deviation of randombred control. H = high line; L = low line A = Fe, Cu adequate (non-stress) diet S = Fe, Cu deficient (stress) diet HA = high PCV line selected on Fe, Cu adequate diet LA = low PCV line selected on Fe, Cu adequate diet HS = high PCV line selected on Fe, Cu deficient (stress) diet LS = low PCV line selected on Fe, Cu deficient (stress) diet
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 20, 2015
which had been mass-selected in divergent directions for 15-day PCV under two nutritional environments. The two nutritional environments were an Fe-Cu adequate, turkey starter diet and an Fe-Cu deficient, skim milk diet. After four generations of selection reciprocal crosses between the various lines were made. Eggs from the randombred quail population maintained at the Southern Regional Poultry Genetics Laboratory as 120 paired matings were obtained each generation, hatched and reared under both the Fe-Cu adequate and the Fe-Cu deficient dietary regimes to serve as controls. Selection procedures and management practices were presented in detail by Stino (1970).
2149
SELECTION FOR PACKED CELL VOLUME
on deviations from controls (sexes combined) of the high and low PCV lines selected on Fe, Cu adequate diet (HA, LA) and high and low PCV lines selected on Fe, Cu deficient (stress) diet (HS, LS). The randombred controls were reared intermingled in each of the selection environments.
TABLE 1.—Phenotypic correlations of unselected traits with 15-day PCV of high and low lines under adequate Fe-Cu and Fe-Cu deficient (stress) diets. Fe-Cu adequate diet HA 2
Population
P, 2 week body wt. - . 1 4 Egg prod. .31 .05 % Fert. % Hatch. .10
LA
s,
S2
s3
--.06 .36 .05 .08
.03 -.01 .13 .01
-.08 .40 .19 .15
X1
P,
s,
S2
s3
-.06 + .27 + .10 + .08
0.14** -.25 -.14 .01
.02 -.36 -.01 -.03
.03 -.09 -.13 .05
.14 -.40 .34 .40*
X + .01 -.28 + .01 + .10
Fe-Cu deficient (stress) diet Population
LS
HS Pi
s,
2 week body wt. .16** .13 Egg prod. .15 --.30 % Fert. -.07 .12 % Hatch. - . 1 5 .12
s2
s3
.14*
.38**
.06 -.04 -.01
.07 -.01 .13
X + .20 0.0 0.0 + .02
P, .16** -.35 .10 -.19
s, -.02 -.44 -.05 .17
s2
s3
X
.14*
.26**
+ .13
-.22 .22 .08
' X = arithmetic mean for all values H = high PCV; L = low PCV; A = adequate Fe, Cu; S = deficient Fe, Cu. "Correlation significant at P s .05. 'Correlation significant at P s .01. 2
-.40 .06 .23
-.35 + .08 + .07
Downloaded from http://ps.oxfordjournals.org/ at East Tennessee State University on June 20, 2015
Body Weight. Differences in 15-day body weight between the high and low PCV lines (within a selection regime) were not significant in any generation or when analyzed over generations. In the S 3 generation the body weight of the controls responded somewhat differently to the environments which resulted in all the selected lines appearing to be heavier in body weight. The mean within-line phenotypic correlations for the four generations between 2 week body weight and PCV (Table 1) were -0.06 for the HA, +0.01 for the LA, +0.20 for the HS and +0.13 for the LS line. The correlations were sometimes significant within a generation. However, the low magnitude of the correlation and comparisons of the
relatively small changes in body weight of the HS line (which had the highest correlation) and other lines which had a lower correlation (example—HA) with randombreds indicate the significance is not a measure of consistent response. Washburn and Edwards (1970) reported a relationship between body weight and PCV depression of chicks fed an Fe, Cu deficient diet. However, in this selection experiment using Japanese quail there appears to be no trend of association of PCV with body weight. Some heterosis for body weight was noted in the S 4 reciprocal cross progeny (Table 2). The crossline progeny were significantly heavier than selected line progeny except for the LA x HA crosses. The differences between the reciprocal crosses were significant (P < .01), in favor of the high PCV male x low PCV male cross (HA x LA). This closer resemblance between progeny average and their sire was reported earlier by Olsen and Knox (1940) in egg weight of chickens, Siegel (1963) in body weight of chickens and Stino and Washburn (1972) in PCV of quails.
2150
K. W. WASHBURN AND F. K. R. STINO
TABLE 2.—Means of 15-day body weight of S4 crosses and fertility and hatchability of their parents
Crosses
HA x HA
1
Fe-Cu adequate diet LA x HA HA x LA LA x LA
RBA
Arithmetic mean
Trait: 2 week body weight
38.4"
41.0C
35.6a
37.68b
36.9
Fertility X Hatch 1-Hatch 2
70.9 75.6 66.1
85.7 88.7 82.6
73.1 72.1 74.0
71.2 67.6 74.7
77.7 82.2 73.2
71.7
Hatchability X 3 Hatch 1-Hatch 2
70.3 68.6 72.0
66.6 70.0 63.2
59.3 68.5 50.0
46.2 40.0 52.3
61.2 71.1 51.2
58.3
3
HS x HS'
LS x HS
HS x LS
LS x LS
RBS
Arith^ metic mean
27.3 ab2
2 0 Qcd
31.2"
24.8"
28.7 bc
26.1
Fertility X Hatch 1-Hatch 2
86.6 92.6 80.6
81.9 79.9 83.9
82.1 85.5 78.6
76.6 81.3 71.8
88.6 91.9 85.3
81.6
Hatchability X 3 Hatch 1-Hatch 2
68.3 72.2 64.4
80.0 81.3 78.7
70.5 67.3 73.6
54.8 56.3 53.2
68.1 73.5 62.5
61.1
Fe-Cu deficient (stress) diet Crosses Trait: 2 week body weight 3
'H = High PCV line, L = Low PCV line; sires listed first in denoting mating. A = Fe-Cu adequate; S 2= Fe-Cu deficient Values with different superscript within diets are significantly different (P s .01) using Duncan (1955) multiple range test. 3 Average of two replicates (500 eggs)
Egg Production. The egg production of all selected lines was decreased in the S, generation (Fig. 1). That of the low PCV lines (both on the adequate and stress diets) remained at a level significantly (P =£ .05) lower than their controls for the duration of the selection. However, those of the high line returned to control levels in subsequent generations and differences between either of the high PCV lines and randombreds were not significant. This depression in egg production in the S l generation cannot be attributed to inbreeding depression since it was slight for that generation. These results indicate an association of egg production with selection for PCV, with lowered PCV being associated with lowered egg production. PCV values higher than that normally found may not affect egg production. This relationship of lowered PCV and
lowered egg production appears not to be a direct effect of PCV. The phenotypic correlations between PCV and body weights within lines were consistently negative for both low lines (-0.28 for LA; -0.35 for LS) which indicates that as the PCV is decreased by selection the mean egg production should increase. If the progress in decreasing the PCV of the two low lines is examined (Fig. 1), considerably more progress was made in selection for the low PCV line in the adequate Fe-Cu environment (non-stress). Little progress was made in selection for low PCV on the Fe-Cu deficient environment although there was more selection pressure on this line than on the adequate low line. However, the egg production of both low lines was depressed. These observations would indicate that the selection pressure for genes contributing to reduced PCV was bringing
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38.1" 2
SELECTION FOR PACKED CELL VOLUME
Fertility. Concomitant changes in fertility of total eggs were noted when divergent selection was made for 15-day PCV under both the Fe-Cu adequate and Fe-Cu deficient dietary environments (Fig. 1). Comparisons between the high and low lines within a selection environment indicate fertility of the high PCV adequate line was higher than the respective low PCV lines for all generations. Although differences between these lines were slight for the S 3 and S 4 generations, the low PCVadequate Fe, Cu line was consistently depressed (significant at P s .05) in fertility compared to the randombred control. When selection was practiced under the Fe-Cu deficient dietary conditions the same trend of decreased fertility of the low PCV line compared to their respective high line was observed. However, fertility was not lower when compared to the randombred control except for the S 3 and S 4 generation. The mean phenotypic correlations of PCV with fertility (Table 1) were +0.10, -0.01, 0.0 and +0.08 for the HA, LA, HS and LS lines, respectively, which would indicate that changes in PCV per se were not the reason for the reduced fertility. If the comparative changes in fertility in the lines over generations are compared (Fig. 1), it is seen that the high and low lines first diverged and then in subsequent generations converged al-
though differences in PCV were greatest in the S4 generations. Under the Fe-Cu adequate feeding regime, reciprocal crosses of the selected lines had higher average fertility than either selected lines (Table 2). The low (LA) male x high (HA) female cross showed more heterosis than the reciprocal cross (HA male x LA female). Under the Fe-Cu stress conditions the reciprocal crosses were intermediate to the selected lines. Hatchability. Individual selection in divergent directions for 15-day PCV resulted in associated changes in hatchability of fertile eggs (Fig. 1). Under the Fe-Cu adequate diet conditions, the high PCV line had significantly (P s .01) higher hatchability than the low PCV line with the randombred being intermediate. Under the Fe-Cu stress diet condition, this trend was apparent after the S, generation. This may be due to the limited progress made in selecting for PCV in the downward direction under the Fe-Cu stress condition until the S 2 generation (Stino, 1971). A possible explanation for this association is that the low hatchability of the low PCV line was due to the anoxia of the low PCV line embryos. The developing embryos require a certain amount of oxygen carrying capacity of their blood. If this requirement is not satisfied, due to severe inherited anemia in this case, the embryo will not be able to develop properly and consequently may die. This also seems reasonable since the hatchability of the low stress line was affected only when progress was made in the downward direction. Hatchability of fertile eggs of S 3 parents in each of two hatches was higher in the high PCV lines than in the low PCV line with the randombred intermediate under the Fe-Cu adequate feeding regime (Table 2). Reciprocal crosses of S 3 parents were intermediate between the selected lines. However, a definite maternal effect was observed in
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into play genes that had a deleterious effect on egg production. Since the PCV of the population on the Fe-Cu deficient diet was already low, natural selection may have been more intense against further genetic depression of PCV, but not against subsequent egg production which was not affected by the 5-15 day stress environment conditions. The depression in egg production observed in all selected lines after one generation may have been due to disruption of the genetic balance in the randombred. This decrease in production was restored in subsequent generations.
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K. W. WASHBURN AND F. K. R. STINO
Temperament. Although temperament was not quantitated, it was visually obvious that both high PCV lines were more nervous than either low PCV line. This observation was most noticeable for the S 3 and S 4 generations. When transferring the breeders a number of high-line individuals were observed to fly against the top of the battery until they collapsed and died. The loss of birds in this way was restricted to the two high PCV lines and was not observed in either the low-lines or the randombreds. This nervousness of the high PCV lines could be due to increased blood pressure (Weiburt and Schlager, 1968) or adrenal or thyroid activity or a combination of these factors. Washburn and Guill (1972) reported that the PCV of White Leghorns was higher than that of heavy breeds, indicating the possibility of associating the known nervousness of Leghorns with higher PCV. If the changes in egg production, fertility and hatchability were due to a direct association with PCV, then differences in PCV and these traits in the original population should be associated. Additional evidence is presented in Table 3 that the changes in egg production, fertility and hatchability that appeared to be associated with extremes of
TABLE 3.—Phenotypic correlations between PCV, egg production rate, fertility and hatchability of randombred Coturnix quail.
Non-selected trait Production Fertility Hatchability
Correlation cJPCV 9 PCV Combined sexes .03 -.07 .003 .06 -.07 .2 .03 -.05 .1
PCV is not a direct effect of PCV. When the production, fertility, hatchability and the packed cell volume of the original population was compared there was no significant correlation. REFERENCES Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Ingram, V. M., 1963. The Hemoglobins in Genetics and Evolution. Columbia University Press, New York, N.Y. Lerner, M. I., 1958. The Genetic Basis of Selection. John Wiley and Sons, Inc. New York, N.Y. Olsen, M. W., and C. W. Knox, 1940. Breeding for egg weight and related characters. Poultry Sci. 19: 254-257. Siegel, P. B., 1963. Selection for breast angle at eight weeks of age. 2. Correlated responses of feathering, body weights and reproductive characteristics. Poultry Sci. 42: 437-449. Stino, F. K. R., 1971. Divergent selection for PCV in the Japanese quail under two environments. Ph.D. Thesis, University of Georgia. Stino, F. K. R., and K. W. Washburn, 1972. Divergent selection for two-week packed erythrocyte volume under two nutritional environments in the Japanese quail. Genetics (In Press). Washburn, K. W., and H. M. Edwards, 1970. Variability in hematological response of chicks fed an iron-copper deficient diet. Poultry Sci. 49: 122-127. Washburn, K. W., and R. A. Guill, 1972. Comparison of hematology between Leghorn-type and heavytype egg production stocks: possible association of hematology and Columbian restriction of plumage. Poultry Sci. 52: 946-950. Weiburt, R. S., andG. Schlager, 1968. A genetic study of blood pressure, hematocrit and plasma cholesterol in aged mice. Life Sciences, Part 2, 7: 1111-1119.
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both hatches, with the low PCV male x high PCV female cross having higher hatchability. The randombred was intermediate and near the mean of the high PCV male x low PCV female cross. Under the Fe-Cu stress feeding conditions, the reciprocal crosses showed heterosis over both selected lines with the randombred hatchability being similar to that of the high PCV line (Table 2). A maternal effect was also present with heterosis, where the high PCV line females showed higher hatchability than the low PCV line females in both hatches.