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Abdominal Fat and Testes Weights in Diverse Genetic Lines of Japanese Quail1
BREEDING AND GENETICS Abdominal Fat and Testes Weights in Diverse Genetic Lines of Japanese Quail 1 H. L. MARKS USDA, ARS, Southeast Poultry Research Laboratory, do University of Georgia, 107 Livestock-Poultry Building, Athens, Georgia 30602
ABSTRACT Six experiments were conducted to investigate abdominal fat levels in mature male and female Japanese quail following selection for 4-wk body weight and to investigate the relationship between testes development and abdominal fat accumulation. The present study utilized P-, T-, and S-line quail selected for more than 75 generations for high 4-wk body weight and also lines divergently selected (16 or more generations) for high (H-SD, H-CD) and low (L-SD, L-CD) 4-wk body weight. Adult males had from two to four times more abdominal fat than females, the reciprocal of abdominal fat patterns in chickens. These differences were observed regardless of the selection environment, direction of selection, or duration of selection. Percentage of abdominal fat was higher in high body weight lines than in low body weight lines, and correlation coefficients between body weight and abdominal fat were moderate to high (mean = .39). Correlations between abdominal fat and testes weights were positive and largest at S wk (r = .62). (Key words: selection, body weight, fat patterns, chickens, correlation coefficients) 1990 Poultry Science 69:1627-1633 INTRODUCTION
Considerable differences exist in the amount of abdominal fat in male and female broiler breeders. Sixteen of 21 sires had no measurable abdominal fat, whereas age comparable dams averaged 3.4% abdominal fat of live body weight (Gyles et al, 1982). Becker and Mirosh (1984) observed abdominal fat levels of .2% and 3.3% in male and female broiler breeders, respectively. Although broiler females at 8 wk of age have a higher percentage of abdominal fat than males (Summers et al, 1965; Goodwin et al, 1969; Washburn et al, 1975; Becker et al, 1979), the difference between sexes is much greater at maturity. Unfortunately, selection for increased body weight in broilers results in the increased deposition of abdominal fat at juvenile ages (Chambers et al, 1981; Cartwright et al, 1988; Marks, 1988). The reasons for sex differences in abdominal fat at maturity are unknown; however, it is assumed that these differences are influenced by the sex hormones. Therefore, information regarding development of the gonads and die deposition of abdominal fat may provide some insight into
Mention of trade names does not imply endorsement to the exclusion of others not mentioned by the authors or by the institution at which they are employed.
explaining differences between sexes in abdominal fat. Information regarding abdominal fat levels in Japanese quail is sparse. Although immature Japanese quail have low levels of abdominal fat (Darden and Marks, 1985), abdominal fat levels at maturity are not greatly different from those observed in mature chickens (Sadjadi and Becker, 1980). Sadjadi and Becker (1980) reported that the percentage of abdominal fat in unselected 58-day-old Japanese quail males was higher than that in female quail, a reversal of the relationship observed in chickens. The purposes of this study were 1) to investigate the effect of long-term selection for body weight on abdominal fat levels in diverse genetic quail lines, 2) to investigate sex differences in abdominal fat in adult Japanese quail, and 3) to investigate the relationship between abdominal fat and testes weights. MATERIALS AND METHODS
The present study involved six experiments; four experiments utilized quail lines (P, T, S) selected for high 4-wk body weight (Marks, 1989) and two experiments involved quail lines (H-SD, L-SD, H-CD, L-CD) divergently selected for 4-wk body weight (Darden and Marks, 1988). Quail in all six experiments received a constant 16-h photoperiod from hatch until the termination of each experiment.
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(Received for publication February 5, 1990)
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Experiment 1
Experiment 2 In Generation 16, adult quail from the H-SD, L-SD, H-CD, and L-CD lines (Darden and Marks, 1988) were used to determine the influence of divergent selection for 4-wk body weight and sex on abdominal fat weight. Quail received their normal selection diets from 0 to 4 wk of age, and thereafter all lines received a commercial gamebird breeder diet. At 147 days of age, 18 quail per line per sex were killed by cervical dislocation and abdominal fat removed and weighed as described in Experiment 1. Testes of males were also removed and weighed to the nearest .001 g. Experiment 3 At 30 days of age in Generation 77, males from the P-, T-, S-, and TP-line (T-line quail reared under the P environment) quail lines were weighed and killed by cervical dislocation to measure the relationship of testes and abdominal fat weights. Quail received their respective selection diets for the duration of this experiment. Abdominal fat was removed from 20 males per line and weighed as in Experiment 1. In addition, testes were removed and weighed as described in Experiment 2 to investigate possible relationships between abdominal fat accumulation and testes weight. Experiment 4 Males from H-SD and H-CD quail lines were utilized in Generation 17 to investigate the
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Experiment 5 In Generation 78, P-, T-, and S-line quail were killed by cervical dislocation at 154 days of age to investigate sex differences in abdominal fat and the relationship in males of abdominal fat and testes weight. All quail received their respective selection diets from 0 to 28 days and thereafter a commercial gamebird breeder diet. Abdominal fat and testes weights were obtained as described in Experiments 1 and 2. Experiment 6 Progeny from P-, T-, S-, and C-line (randombred control) quail breeders in Generation 78 were utilized to compare abdominal fat and testes weights at different ages when fed a common diet. In this experiment, all birds received a 28% protein diet from 0 to 42 days of age. Starting at 21 days approximately 15 to 20 males per line were killed by cervical dislocation at 7-day intervals to obtain abdominal fat and testes weights. These data were obtained as described in Experiments 1 and 2. Statistical Analysis Analyses of variance based on a factorial arrangement of treatments were utilized in a fixed model on a within experiment basis to compare the effects of lines and sex on body weight, abdominal fat weight, and percentage of abdominal fat (abdominal fat + body weight). The following model describes the effect of each of the variables studied: Yijk = \n + Li + Sj + (LS)ij + ejjt where \i is the common mean; 1^ is the effect of the i*" line; and Sj is the effect of the j " 1 sex; and LSy is the interaction of the i& line with the j 1 " sex; and ey^ is random error. The model used for analyses of testes weight and percent testes weight (testes weight + body weight) data was as follows:
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Adult P- and T-line quail from the 74th generation were utilized to measure sex differences in abdominal fat. Quail received their respective selection diets (Marks and Lepore, 1968) from 0 to 4 wk of age and thereafter they received a commercial gamebird breeder diet.2 Twenty-four (12 per sex) quail from each line were weighed and killed by cervical dislocation at approximately 119 days of age. Abdominal fat (including gizzard fat) was removed and weighed to the nearest .001 g. Percentage of abdominal fat was calculated by dividing the abdominal fat weight by the live body weight.
relationship between abdominal fat weight and testes development. Quail received their respective selection diets from 0 to 28 days of age and thereafter they received a commercial gamebird breeder diet. At 36 days of age, 20 males from each line were weighed, killed by cervical dislocation, and abdominal fat and testes data obtained as described in Experiments 1 and 2.
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ABDOMINAL FAT AND TESTES WEIGHTS
TABLE 1. Body weights (g) and percentages of abdominal fat by sex in mature P, T, and S lines of quail selected for high 4-wk body weight (Experiments I and 5) P line Sex1
74
M F (M+F) M F (M+F)
275 b 332a .83 285 b 331 a .86
78
T line
S line
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
1.32a .72 b 1.83 2.01 b .54b 3.72
234 b 292 a .80 230 b 294 a .78
2.96a 1.59b 1.86 2.38a 1.54b 2.58
263 b 321 a .82
1.71a .75 b 2.28
"^Means within a trait and generation with no common superscript differ significantly (P<05). l M = male; F = female.
Yij = \i + U + ey where [i is the common mean; Lj is the effect of the i m line; and ey is random error. The general linear model (GLM) and correlation (CORR) procedures of the SAS Institute (1985) were utilized with line means compared by using Duncan's multiple range test when significance among means was detected. RESULTS AND DISCUSSION
Body Weight and Abdominal Fat Adult body weights of female quail were significantly (P<.05) larger (approximately 20%) than body weights of males at 119 days (Experiment 1) and 154 days (Experiment 5) (Table 1). Male:female body weight ratios were rather consistent across both lines and experiments ranging from .78 to .86. Differences in adult body weight between sexes in P, T, and S lines were similar to those observed in these lines in Generations 37 and 38 (Marks, 1978) and also similar to differences reported by Wilson etal. (1961) between sexes in unselected quail. Sadjadi and Becker (1980), however, reported smaller sex differences in body weight at 58 days of age in an unselected quail population. Percentage of abdominal fat was significantly (P<05) higher in male than female quail across lines in both Generations 74 and 78 (Table 1). Male:female ratios ranged from 1.83 to 3.72 with a mean of 2.25. Percentage of abdominal fat in these lines at maturity following 74 and 78 generations of selection was not greatly different from that reported for unselected quail (Sadjadi
and Becker, 1980). However, in Experiment 6 of the present study, selected quail had approximately twice the level of abdominal fat as the unselected control population at 6 wk of age. Although substantial sex differences are present in abdominal fat in sexually mature quail, no significant sex differences in percentage carcass lipid were observed in 28-day-old P and T quail fed diets containing varying levels of protein (Marks, 1971). Also Edwards (1981) found that sex did not have a significant effect on H2O, protein, ash, and lipid content from 14 to 49 days in an unselected quail line. Therefore, sex differences in abdominal fat must occur at some point after sexual maturity, because Wyatt et al. (1982) reported a highly positive correlation between percentage of carcass lipid and percentage of abdominal fat in female quail at 8 wk of age. In both Generations 74 and 78, percentage of abdominal fat was significantly (P<.05) greater in the T line than in the P line (Table 1). These data indicate that selection for body weight under a high protein diet environment (P line) may result in less abdominal fat at maturity than selection under a low protein diet containing thiouracil (T line). Mature body weights (112 day) of female quail divergently selected for high and low 4-wk body weight were significantly (P<.05) heavier than those of males (Table 2). The male: female body weight ratios were larger in the high lines (H-SD and H-CD) than in the low lines (LSD and L-CD), and the mean ratio (.90) across lines was also larger than the mean ratio (.82) obtained for the P, T, and S lines (Table 1) that had undergone selection for more generations. Percentages of abdominal fat were significantly (P<.05) higher in males than females in
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Generation
Body weight
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TABLE 2. Body weights (g) and percentages of abdonunal fat in mature male and female H-SD, L-SD, H-CD, and L-CD quail in Generation 16 (Experiment 2)1 Line H-CD
H-SD
L-SD
L-CD
Body weight
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
M F M:F
194b 203* .96
5.3* 1.9b 2.79
188b 207*
3.3* 1.4b 2.41
82 b 93* .88
1.2* 0.3 b 4.14
77 b 91* .84
1.1* 0.4b 2.75
.91
"^Means within trait with no common superscript differ significantly (P<05). UJnes H-SD and H-CD were selected for increased 4-wk body weight while Lines L-SD and L-CD were selected for decreased 4-wk body weight. M = male: F = female.
both high and low body weight lines (Table 2). Percentages of abdominal fat levels were also significantly (P<.05) higher in the high body weight lines (H-SD and H-CD) than in the low body weight lines (L-SD and L-CD). However, the mean male:female ratio for the low lines (3.4) was greater than the mean ratio observed for the high lines (2.6). Higher abdominal fat levels in male quail than in female quail (Tables 1 and 2) are the reciprocal of sex differences observed in abdominal fat in broiler breeders. Gyles et al. (1982) and Becker and Mirosh (1984) found extremely low levels of abdominal fat in broiler breeder males (<.5%) and moderate to high levels in female breeders (3 to 4%). The reciprocally different abdominal fat levels between sexes in adult quail and broiler breeders suggest that comparative studies between these two species may be helpful in delineating mechanisms responsible for sex differences in the accumulation of abdominal fat. In both situations, the sex with the slowest gain and the lowest adult body weight had the highest percentage of abdominal fat. Abdominal Fat and Testes Weight Significant (P<.05) body weight differences were observed among males in the P, T, S, and TP lines in Generation 77, with P-line quail having the largest and T-line quail the smallest weights at 30 days of age (Table 3). Abdominal fat, testes weights, and percentage of testes weights were significantly higher in P and TP lines than in T and S lines. The presence of thiouracil in the diets of T and S line quail from 0 to 28 days undoubtedly contributed to lower body weights; however, percentage abdominal
fat and testes values were also significantly (P<.05) lower in the S line. When expressed as a percentage, both fat and testes were significantly (P<05) larger in the TP line than in the other lines. Lower testes weights in S line quail are in agreement with previous observations regarding retarded testes development in this line (Burke and Marks, 1984). The low testes weights in the S line were accompanied by the lowest abdominal fat values on both an absolute and percentage bases. Although S-line values were smaller than the comparable T-line values, testes weight and percentage of testes weight differences between lines were not significantly different. Although the part-whole relationships often influence organ development patterns, the relationship between percentage of fat and percentage of testes follow identical rank (i.e., highest to lowest TP > P > T > S). However, the rankings of body weight do not follow the rankings of these two traits. Therefore, these data suggest a relationship between percentage of fat and percentage of testes, which may be independent of body weight change. Males from the H-SD and H-CD lines had similar abdominal fat and testes weights at 36 days of age in Generation 17 (Table 4). The lack of significant differences for these traits was likely due to larger coefficients of variation compared with variation in body weights. There was evidence, however, that H-CD males, which had a higher percentage of testes weights, also had a higher percentage of fat weights than HSD males. Correlation coefficients between body weight and abdominal fat, body weight and testes weight, and abdominal fat and testes weight for the P, T, S, and TP lines in Generation
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Sex 2
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ABDOMINAL FAT AND TESTES WEIGHTS TABLE 3 . Mean body, abdominal fat, and testes weight (g) for P, T, S, and TP male quail at 30 days of age (C feneration 77) (Experiment 3)
Line
Body weight
Fat weight
Testes weight
Percentage fat2
Percentage testes
P T S TP
235* 170d 214 b 187°
1.10* .77b .64" 1.24*
1.12* .39b .29b 1.43*
.47b .45" .30° .66*
.48b .23 c .13° .76*
TABLE 4. Mean body, abdominal fat, and testes we ight (g) for H-SD and H-CD quail lines at 36 days of age (Generation 17) (Experiment 4)
Line
Body weight
H-SD H-CD
114b 126*
Fat weight
Testes weight
Percentage fat2
Percentage testes3
1.07* 1.33"
.55* .67*
.92* 1.05*
(r\
\6) .64* .85*
*^Means within a trait with no common superscripts differ significantly (P<05). ^ines were selected for increased 4-wk body weight 2 (Abdominal fat weight + body weight) x 100. 3 (Testes weight + body weight) x 100.
78 are shown in Table 5. Correlations between body weight and abdominal fat were positive and ranged from .23 to .56. The mean of these values (.39) in males was higher than the correlation (.22) at 56 days in female quail (Wyatt et al., 1982). However, these correlations in quail are similar to correlations between body weight and abdominal fat in broilers (Marks, 1988). Correlations between body and testes weights were positive and similar in magnitude to those between body and abdominal fat weights (.16 to .41). Two of four correlations between abdominal fat weight and testes weight were significant (P<.01) with a pooled correlation across lines of .66. The correlations (body weight:abdominal fat and body weight:testes weight) are part-whole correlations and, therefore, would be expected to be positive and of moderate magnitude. The relationship, however, between abdominal fat and testes weight is interesting, because in animals where the female is the homogametic sex, a positive relationship apparently exists between fat accumulation and sexual maturity (Frisch, 1980).
The correlation coefficients between body weight and abdominal fat, body weight and testes weight, and abdominal fat weight and testes weight at 21,28,35, and 42 days of age in P-, T-, S-, and C-quail lines are presented in Table 6. Data were in general similar to those obtained in Experiment 5 (Table 5). However, the pooled part-whole correlations between body weight and abdominal fat weight and
TABLE 5. Correlation coefficients of body weight, abdominal fat weight, and testes weight in P-, T-, S-, and TP-line quail (Experiment 5)1 Line Correlation
P
T
S
TP
Body weighffat Body weighttestes Fatrtestes
.38 .36 .37
.56** .41 .60**
.41 .40 .37
.23 .16 .60**
All lines of quail were selected for increased 4-wk body weight. *P<05. **P<01.
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^Means within a trait with no common superscripts differ significantly (P<05). 1 Lines were selected for increased 4-wk body weight 2 (Abdominal fat weight + body weight) x 100. 3 (Testes weight + body weight) x 100.
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TABLE 6. Correlation coefficients of body, abdominal fat, and testes weights in P-, T-, S-, and C-line quail at 21, 28, 35, and 42 days of age (Experiment 6) Lines Days
Body weight fat Body weight: testes Fat:testes Body weight: fat Body weight testes Fat:testes Body weight: fat Body weight: testes Fat:testes Body weight: fat Body weight: testes Fat:testes
21
2h
35
42
Pooled .52* .29 .20 .43 .05 .47* .51* .29 .77** .33 .33 .06
.57* .45 .23 .28 .12 .51* ,29 ,22 .60** .34 ,13 .30
.67** .32 .26
.52* .34 .52* .62** -.19 .29 .16 .13 .60*
,16 .65 ,20 .34 .61 .15 .64** .80** .77** .77* .20 .50
73** 47** 46** 65** 37** 55** 74** 38** 62** 74** .42** 51**
Lines P, T, and S were selected for increased 4-wk body weight. Line C was a randombred control. *P<05. **P<01.
between body weight and testes weight were larger than those previously observed. Perhaps the most striking feature of these data was the constant correlations of body weight:abdominal
BW:FAT
z
o UJ
oc DC
o u
WEEK
FIGURE 1. Correlation coefficients across four quail lines (P, T, S, and C) between body weight and abdominal fat weight (BW:FAT), body weight and testes weight (BW: TESTES) and fat weight and testes weight (FATiTESTES). Within correlations between the same traits, different letters indicate significantly different (P<05) weekly means.
fat and body weight:testes weight across weeks, whereas correlations between abdominal fat and testes weight increased from 21 to 35 days of age and then declined at 42 days (Figure 1). Correlations of abdominal fat and testes weight obtained at 112 days of age in Generation 78 for P, T, and S lines were -.24, .11, and .27, respectively (unpublished). These data indicate a stronger relationship between these variables just prior to sexual maturity (35 days) than at other ages and may be important in view of the apparent relationship between pubertal adipose tissue and normal sexual maturation of females where females are the smaller of the two sexes (Frisch, 1980). Because the quail male has lower body weight with greater percentages of abdominal fat, the concurrent development of gonadal and adipose tissue may be necessary for sexual maturation. However, it is unknown if a cause-and-effect relationship exists, because both gonad weight and abdominal fat levels would be expected to increase prior to sexual maturity. The reciprocal sex accumulation of abdominal fat in quail, unlike chickens, indicates that comparative studies using the quail and chicken might provide insight into both sex differences in growth as well as in abdominal fat accumulation. REFERENCES Becker, W. A., and L. W. Mirosh, 1984. Abdominal fat in broiler breeders. Poultry Sci. 63:819-821. Becker, W. A., J. V. Spencer, L. W. Mirosh, and J. A.
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Correlation
ABDOMINAL FAT AND TESTES WEIGHTS
50:1753-1761. Marks, H. L., 1978. Growth curve changes associated with long term selection for body weight in Japanese quail. Growth 42:129-140. Marks, H. L., 1988. Genetic manipulation of abdominal fat in broilers. CRC Crit Rev. Poult Biol. 1:271-284. Marks, H. L., 1989. Long-term selection for four-week body in Japanese quail following modification of the selection environment. Poultry Sci. 68:455-459. Marks, H. L., and P. D. Lepore, 1968. Growth rate inheritance in Japanese quail. 1. The establishment of environmental conditions which restrict juvenile growth rate. Poultry Sci. 47:556-560. Sadjadi, M., and W. A. Becker, 1980. Heritability and genetic correlations of body weight and surgically removed abdominal fat in Coturnix quail. Poultry Sci. 59:1977-1984. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Ed. SAS Inst Inc., Cary, NC. Summers, J. D., S. J. Slinger, and G. C. Ashton, 1965. The effect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poultry Sci. 44:513-520. Washburn, K. W., R. A. Guill, and H. M. Edwards, Jr., 1975. Influence of genetic differences in feed efficiency on carcass composition of young chickens. J. Nutr. 105: 1311-1317. Wilson, W. O., U. K. Abbott, and H. Abplanalp, 1961. Evaluation of Coturnix (Japanese quail) as pilot animal for poultry. Poultry Sci. 40:651-657. Wyatt, J.M.F., P. B. Siegel, and J. H. Cherry, 1982. Phenotypic relationships between adiposity, breast weight, and body weight in female Japanese quail. Poultry Sci. 61:643-646.
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Verstrate, 1979. Prediction of fat and fat free live weight in broiler chickens using backskin fat, abdominal fat, and live body weight. Poultry Sci. 58:835-842. Burke, W. H., and H. L. Marks, 1984. Gonad growth and plasma luteinizing hormone levels in quail {Coturnix coturnix japonica) selected for high four-week body weight Poultry Sci. 63(Suppl. 1):72. (Abstr.) Cartwright, A. L., H. L. Marks, and D. R. Campion, 1988. Adipose cellularity in nonselected and selected broiler stocks: measurements at equal weights and ages. Poultry Sci. 67:1338-1344. Chambers, J. R., J. S. Gavora, and A. Fortin, 1981. Genetic changes in meat-type chickens in the last twenty years. Can. J. Anim. Sci. 61:555-563. Darden, J. R., and H. L. Marks, 1985. The influence of dietary salt on water consumption and carcass lipids in Japanese quail. Poultry Sci. 64:1269-1278. Darden, J. R., and H. L. Marks, 1988. Divergent selectionfor growth in Japanese quail under split and complete nutritional environments. 1. Genetic and correlated responses to selection. Poultry Sci. 67:519—529. Edwards, H. M., Jr., 1981. Carcass composition studies. 3. Influences of age, sex and calorie-protein content of the diet on carcass composition of Japanese quail. Poultry Sci. 60:2506-2512. Frisch, R. E., 1980. Pubertal adipose tissue: is it necessary for normal sexual maturation? Evidence from the rat and human female. Fed. Proc. 39:2395-2400. Goodwin, T. L., L. D. Andrews, and J. E. Webb, 1969. The influence of age, sex, and energy level on tenderness of broilers. Poultry Sci. 48:548-551. Gyles, N. R., A. Maeza, and T. L. Goodwin, 1982. Regression of abdominal fat in broilers and abdominal fat in spent parents. Poultry Sci. 61:1809-1814. Marks, H. L., 1971. Evaluation of growth selected quail lines under different nutritional environments. Poultry Sci.
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ABSTRACT Six experiments were conducted to investigate abdominal fat levels in mature male and female Japanese quail following selection for 4-wk body weight and to investigate the relationship between testes development and abdominal fat accumulation. The present study utilized P-, T-, and S-line quail selected for more than 75 generations for high 4-wk body weight and also lines divergently selected (16 or more generations) for high (H-SD, H-CD) and low (L-SD, L-CD) 4-wk body weight. Adult males had from two to four times more abdominal fat than females, the reciprocal of abdominal fat patterns in chickens. These differences were observed regardless of the selection environment, direction of selection, or duration of selection. Percentage of abdominal fat was higher in high body weight lines than in low body weight lines, and correlation coefficients between body weight and abdominal fat were moderate to high (mean = .39). Correlations between abdominal fat and testes weights were positive and largest at S wk (r = .62). (Key words: selection, body weight, fat patterns, chickens, correlation coefficients) 1990 Poultry Science 69:1627-1633 INTRODUCTION
Considerable differences exist in the amount of abdominal fat in male and female broiler breeders. Sixteen of 21 sires had no measurable abdominal fat, whereas age comparable dams averaged 3.4% abdominal fat of live body weight (Gyles et al, 1982). Becker and Mirosh (1984) observed abdominal fat levels of .2% and 3.3% in male and female broiler breeders, respectively. Although broiler females at 8 wk of age have a higher percentage of abdominal fat than males (Summers et al, 1965; Goodwin et al, 1969; Washburn et al, 1975; Becker et al, 1979), the difference between sexes is much greater at maturity. Unfortunately, selection for increased body weight in broilers results in the increased deposition of abdominal fat at juvenile ages (Chambers et al, 1981; Cartwright et al, 1988; Marks, 1988). The reasons for sex differences in abdominal fat at maturity are unknown; however, it is assumed that these differences are influenced by the sex hormones. Therefore, information regarding development of the gonads and die deposition of abdominal fat may provide some insight into
Mention of trade names does not imply endorsement to the exclusion of others not mentioned by the authors or by the institution at which they are employed.
explaining differences between sexes in abdominal fat. Information regarding abdominal fat levels in Japanese quail is sparse. Although immature Japanese quail have low levels of abdominal fat (Darden and Marks, 1985), abdominal fat levels at maturity are not greatly different from those observed in mature chickens (Sadjadi and Becker, 1980). Sadjadi and Becker (1980) reported that the percentage of abdominal fat in unselected 58-day-old Japanese quail males was higher than that in female quail, a reversal of the relationship observed in chickens. The purposes of this study were 1) to investigate the effect of long-term selection for body weight on abdominal fat levels in diverse genetic quail lines, 2) to investigate sex differences in abdominal fat in adult Japanese quail, and 3) to investigate the relationship between abdominal fat and testes weights. MATERIALS AND METHODS
The present study involved six experiments; four experiments utilized quail lines (P, T, S) selected for high 4-wk body weight (Marks, 1989) and two experiments involved quail lines (H-SD, L-SD, H-CD, L-CD) divergently selected for 4-wk body weight (Darden and Marks, 1988). Quail in all six experiments received a constant 16-h photoperiod from hatch until the termination of each experiment.
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(Received for publication February 5, 1990)
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MASKS
Experiment 1
Experiment 2 In Generation 16, adult quail from the H-SD, L-SD, H-CD, and L-CD lines (Darden and Marks, 1988) were used to determine the influence of divergent selection for 4-wk body weight and sex on abdominal fat weight. Quail received their normal selection diets from 0 to 4 wk of age, and thereafter all lines received a commercial gamebird breeder diet. At 147 days of age, 18 quail per line per sex were killed by cervical dislocation and abdominal fat removed and weighed as described in Experiment 1. Testes of males were also removed and weighed to the nearest .001 g. Experiment 3 At 30 days of age in Generation 77, males from the P-, T-, S-, and TP-line (T-line quail reared under the P environment) quail lines were weighed and killed by cervical dislocation to measure the relationship of testes and abdominal fat weights. Quail received their respective selection diets for the duration of this experiment. Abdominal fat was removed from 20 males per line and weighed as in Experiment 1. In addition, testes were removed and weighed as described in Experiment 2 to investigate possible relationships between abdominal fat accumulation and testes weight. Experiment 4 Males from H-SD and H-CD quail lines were utilized in Generation 17 to investigate the
-Purina Mills Inc., St. Louis, MO 63166-6812.
Experiment 5 In Generation 78, P-, T-, and S-line quail were killed by cervical dislocation at 154 days of age to investigate sex differences in abdominal fat and the relationship in males of abdominal fat and testes weight. All quail received their respective selection diets from 0 to 28 days and thereafter a commercial gamebird breeder diet. Abdominal fat and testes weights were obtained as described in Experiments 1 and 2. Experiment 6 Progeny from P-, T-, S-, and C-line (randombred control) quail breeders in Generation 78 were utilized to compare abdominal fat and testes weights at different ages when fed a common diet. In this experiment, all birds received a 28% protein diet from 0 to 42 days of age. Starting at 21 days approximately 15 to 20 males per line were killed by cervical dislocation at 7-day intervals to obtain abdominal fat and testes weights. These data were obtained as described in Experiments 1 and 2. Statistical Analysis Analyses of variance based on a factorial arrangement of treatments were utilized in a fixed model on a within experiment basis to compare the effects of lines and sex on body weight, abdominal fat weight, and percentage of abdominal fat (abdominal fat + body weight). The following model describes the effect of each of the variables studied: Yijk = \n + Li + Sj + (LS)ij + ejjt where \i is the common mean; 1^ is the effect of the i*" line; and Sj is the effect of the j " 1 sex; and LSy is the interaction of the i& line with the j 1 " sex; and ey^ is random error. The model used for analyses of testes weight and percent testes weight (testes weight + body weight) data was as follows:
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Adult P- and T-line quail from the 74th generation were utilized to measure sex differences in abdominal fat. Quail received their respective selection diets (Marks and Lepore, 1968) from 0 to 4 wk of age and thereafter they received a commercial gamebird breeder diet.2 Twenty-four (12 per sex) quail from each line were weighed and killed by cervical dislocation at approximately 119 days of age. Abdominal fat (including gizzard fat) was removed and weighed to the nearest .001 g. Percentage of abdominal fat was calculated by dividing the abdominal fat weight by the live body weight.
relationship between abdominal fat weight and testes development. Quail received their respective selection diets from 0 to 28 days of age and thereafter they received a commercial gamebird breeder diet. At 36 days of age, 20 males from each line were weighed, killed by cervical dislocation, and abdominal fat and testes data obtained as described in Experiments 1 and 2.
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TABLE 1. Body weights (g) and percentages of abdominal fat by sex in mature P, T, and S lines of quail selected for high 4-wk body weight (Experiments I and 5) P line Sex1
74
M F (M+F) M F (M+F)
275 b 332a .83 285 b 331 a .86
78
T line
S line
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
1.32a .72 b 1.83 2.01 b .54b 3.72
234 b 292 a .80 230 b 294 a .78
2.96a 1.59b 1.86 2.38a 1.54b 2.58
263 b 321 a .82
1.71a .75 b 2.28
"^Means within a trait and generation with no common superscript differ significantly (P<05). l M = male; F = female.
Yij = \i + U + ey where [i is the common mean; Lj is the effect of the i m line; and ey is random error. The general linear model (GLM) and correlation (CORR) procedures of the SAS Institute (1985) were utilized with line means compared by using Duncan's multiple range test when significance among means was detected. RESULTS AND DISCUSSION
Body Weight and Abdominal Fat Adult body weights of female quail were significantly (P<.05) larger (approximately 20%) than body weights of males at 119 days (Experiment 1) and 154 days (Experiment 5) (Table 1). Male:female body weight ratios were rather consistent across both lines and experiments ranging from .78 to .86. Differences in adult body weight between sexes in P, T, and S lines were similar to those observed in these lines in Generations 37 and 38 (Marks, 1978) and also similar to differences reported by Wilson etal. (1961) between sexes in unselected quail. Sadjadi and Becker (1980), however, reported smaller sex differences in body weight at 58 days of age in an unselected quail population. Percentage of abdominal fat was significantly (P<05) higher in male than female quail across lines in both Generations 74 and 78 (Table 1). Male:female ratios ranged from 1.83 to 3.72 with a mean of 2.25. Percentage of abdominal fat in these lines at maturity following 74 and 78 generations of selection was not greatly different from that reported for unselected quail (Sadjadi
and Becker, 1980). However, in Experiment 6 of the present study, selected quail had approximately twice the level of abdominal fat as the unselected control population at 6 wk of age. Although substantial sex differences are present in abdominal fat in sexually mature quail, no significant sex differences in percentage carcass lipid were observed in 28-day-old P and T quail fed diets containing varying levels of protein (Marks, 1971). Also Edwards (1981) found that sex did not have a significant effect on H2O, protein, ash, and lipid content from 14 to 49 days in an unselected quail line. Therefore, sex differences in abdominal fat must occur at some point after sexual maturity, because Wyatt et al. (1982) reported a highly positive correlation between percentage of carcass lipid and percentage of abdominal fat in female quail at 8 wk of age. In both Generations 74 and 78, percentage of abdominal fat was significantly (P<.05) greater in the T line than in the P line (Table 1). These data indicate that selection for body weight under a high protein diet environment (P line) may result in less abdominal fat at maturity than selection under a low protein diet containing thiouracil (T line). Mature body weights (112 day) of female quail divergently selected for high and low 4-wk body weight were significantly (P<.05) heavier than those of males (Table 2). The male: female body weight ratios were larger in the high lines (H-SD and H-CD) than in the low lines (LSD and L-CD), and the mean ratio (.90) across lines was also larger than the mean ratio (.82) obtained for the P, T, and S lines (Table 1) that had undergone selection for more generations. Percentages of abdominal fat were significantly (P<.05) higher in males than females in
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Generation
Body weight
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TABLE 2. Body weights (g) and percentages of abdonunal fat in mature male and female H-SD, L-SD, H-CD, and L-CD quail in Generation 16 (Experiment 2)1 Line H-CD
H-SD
L-SD
L-CD
Body weight
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
Body weight
Percentage fat
M F M:F
194b 203* .96
5.3* 1.9b 2.79
188b 207*
3.3* 1.4b 2.41
82 b 93* .88
1.2* 0.3 b 4.14
77 b 91* .84
1.1* 0.4b 2.75
.91
"^Means within trait with no common superscript differ significantly (P<05). UJnes H-SD and H-CD were selected for increased 4-wk body weight while Lines L-SD and L-CD were selected for decreased 4-wk body weight. M = male: F = female.
both high and low body weight lines (Table 2). Percentages of abdominal fat levels were also significantly (P<.05) higher in the high body weight lines (H-SD and H-CD) than in the low body weight lines (L-SD and L-CD). However, the mean male:female ratio for the low lines (3.4) was greater than the mean ratio observed for the high lines (2.6). Higher abdominal fat levels in male quail than in female quail (Tables 1 and 2) are the reciprocal of sex differences observed in abdominal fat in broiler breeders. Gyles et al. (1982) and Becker and Mirosh (1984) found extremely low levels of abdominal fat in broiler breeder males (<.5%) and moderate to high levels in female breeders (3 to 4%). The reciprocally different abdominal fat levels between sexes in adult quail and broiler breeders suggest that comparative studies between these two species may be helpful in delineating mechanisms responsible for sex differences in the accumulation of abdominal fat. In both situations, the sex with the slowest gain and the lowest adult body weight had the highest percentage of abdominal fat. Abdominal Fat and Testes Weight Significant (P<.05) body weight differences were observed among males in the P, T, S, and TP lines in Generation 77, with P-line quail having the largest and T-line quail the smallest weights at 30 days of age (Table 3). Abdominal fat, testes weights, and percentage of testes weights were significantly higher in P and TP lines than in T and S lines. The presence of thiouracil in the diets of T and S line quail from 0 to 28 days undoubtedly contributed to lower body weights; however, percentage abdominal
fat and testes values were also significantly (P<.05) lower in the S line. When expressed as a percentage, both fat and testes were significantly (P<05) larger in the TP line than in the other lines. Lower testes weights in S line quail are in agreement with previous observations regarding retarded testes development in this line (Burke and Marks, 1984). The low testes weights in the S line were accompanied by the lowest abdominal fat values on both an absolute and percentage bases. Although S-line values were smaller than the comparable T-line values, testes weight and percentage of testes weight differences between lines were not significantly different. Although the part-whole relationships often influence organ development patterns, the relationship between percentage of fat and percentage of testes follow identical rank (i.e., highest to lowest TP > P > T > S). However, the rankings of body weight do not follow the rankings of these two traits. Therefore, these data suggest a relationship between percentage of fat and percentage of testes, which may be independent of body weight change. Males from the H-SD and H-CD lines had similar abdominal fat and testes weights at 36 days of age in Generation 17 (Table 4). The lack of significant differences for these traits was likely due to larger coefficients of variation compared with variation in body weights. There was evidence, however, that H-CD males, which had a higher percentage of testes weights, also had a higher percentage of fat weights than HSD males. Correlation coefficients between body weight and abdominal fat, body weight and testes weight, and abdominal fat and testes weight for the P, T, S, and TP lines in Generation
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Sex 2
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ABDOMINAL FAT AND TESTES WEIGHTS TABLE 3 . Mean body, abdominal fat, and testes weight (g) for P, T, S, and TP male quail at 30 days of age (C feneration 77) (Experiment 3)
Line
Body weight
Fat weight
Testes weight
Percentage fat2
Percentage testes
P T S TP
235* 170d 214 b 187°
1.10* .77b .64" 1.24*
1.12* .39b .29b 1.43*
.47b .45" .30° .66*
.48b .23 c .13° .76*
TABLE 4. Mean body, abdominal fat, and testes we ight (g) for H-SD and H-CD quail lines at 36 days of age (Generation 17) (Experiment 4)
Line
Body weight
H-SD H-CD
114b 126*
Fat weight
Testes weight
Percentage fat2
Percentage testes3
1.07* 1.33"
.55* .67*
.92* 1.05*
(r\
\6) .64* .85*
*^Means within a trait with no common superscripts differ significantly (P<05). ^ines were selected for increased 4-wk body weight 2 (Abdominal fat weight + body weight) x 100. 3 (Testes weight + body weight) x 100.
78 are shown in Table 5. Correlations between body weight and abdominal fat were positive and ranged from .23 to .56. The mean of these values (.39) in males was higher than the correlation (.22) at 56 days in female quail (Wyatt et al., 1982). However, these correlations in quail are similar to correlations between body weight and abdominal fat in broilers (Marks, 1988). Correlations between body and testes weights were positive and similar in magnitude to those between body and abdominal fat weights (.16 to .41). Two of four correlations between abdominal fat weight and testes weight were significant (P<.01) with a pooled correlation across lines of .66. The correlations (body weight:abdominal fat and body weight:testes weight) are part-whole correlations and, therefore, would be expected to be positive and of moderate magnitude. The relationship, however, between abdominal fat and testes weight is interesting, because in animals where the female is the homogametic sex, a positive relationship apparently exists between fat accumulation and sexual maturity (Frisch, 1980).
The correlation coefficients between body weight and abdominal fat, body weight and testes weight, and abdominal fat weight and testes weight at 21,28,35, and 42 days of age in P-, T-, S-, and C-quail lines are presented in Table 6. Data were in general similar to those obtained in Experiment 5 (Table 5). However, the pooled part-whole correlations between body weight and abdominal fat weight and
TABLE 5. Correlation coefficients of body weight, abdominal fat weight, and testes weight in P-, T-, S-, and TP-line quail (Experiment 5)1 Line Correlation
P
T
S
TP
Body weighffat Body weighttestes Fatrtestes
.38 .36 .37
.56** .41 .60**
.41 .40 .37
.23 .16 .60**
All lines of quail were selected for increased 4-wk body weight. *P<05. **P<01.
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^Means within a trait with no common superscripts differ significantly (P<05). 1 Lines were selected for increased 4-wk body weight 2 (Abdominal fat weight + body weight) x 100. 3 (Testes weight + body weight) x 100.
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TABLE 6. Correlation coefficients of body, abdominal fat, and testes weights in P-, T-, S-, and C-line quail at 21, 28, 35, and 42 days of age (Experiment 6) Lines Days
Body weight fat Body weight: testes Fat:testes Body weight: fat Body weight testes Fat:testes Body weight: fat Body weight: testes Fat:testes Body weight: fat Body weight: testes Fat:testes
21
2h
35
42
Pooled .52* .29 .20 .43 .05 .47* .51* .29 .77** .33 .33 .06
.57* .45 .23 .28 .12 .51* ,29 ,22 .60** .34 ,13 .30
.67** .32 .26
.52* .34 .52* .62** -.19 .29 .16 .13 .60*
,16 .65 ,20 .34 .61 .15 .64** .80** .77** .77* .20 .50
73** 47** 46** 65** 37** 55** 74** 38** 62** 74** .42** 51**
Lines P, T, and S were selected for increased 4-wk body weight. Line C was a randombred control. *P<05. **P<01.
between body weight and testes weight were larger than those previously observed. Perhaps the most striking feature of these data was the constant correlations of body weight:abdominal
BW:FAT
z
o UJ
oc DC
o u
WEEK
FIGURE 1. Correlation coefficients across four quail lines (P, T, S, and C) between body weight and abdominal fat weight (BW:FAT), body weight and testes weight (BW: TESTES) and fat weight and testes weight (FATiTESTES). Within correlations between the same traits, different letters indicate significantly different (P<05) weekly means.
fat and body weight:testes weight across weeks, whereas correlations between abdominal fat and testes weight increased from 21 to 35 days of age and then declined at 42 days (Figure 1). Correlations of abdominal fat and testes weight obtained at 112 days of age in Generation 78 for P, T, and S lines were -.24, .11, and .27, respectively (unpublished). These data indicate a stronger relationship between these variables just prior to sexual maturity (35 days) than at other ages and may be important in view of the apparent relationship between pubertal adipose tissue and normal sexual maturation of females where females are the smaller of the two sexes (Frisch, 1980). Because the quail male has lower body weight with greater percentages of abdominal fat, the concurrent development of gonadal and adipose tissue may be necessary for sexual maturation. However, it is unknown if a cause-and-effect relationship exists, because both gonad weight and abdominal fat levels would be expected to increase prior to sexual maturity. The reciprocal sex accumulation of abdominal fat in quail, unlike chickens, indicates that comparative studies using the quail and chicken might provide insight into both sex differences in growth as well as in abdominal fat accumulation. REFERENCES Becker, W. A., and L. W. Mirosh, 1984. Abdominal fat in broiler breeders. Poultry Sci. 63:819-821. Becker, W. A., J. V. Spencer, L. W. Mirosh, and J. A.
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ABDOMINAL FAT AND TESTES WEIGHTS
50:1753-1761. Marks, H. L., 1978. Growth curve changes associated with long term selection for body weight in Japanese quail. Growth 42:129-140. Marks, H. L., 1988. Genetic manipulation of abdominal fat in broilers. CRC Crit Rev. Poult Biol. 1:271-284. Marks, H. L., 1989. Long-term selection for four-week body in Japanese quail following modification of the selection environment. Poultry Sci. 68:455-459. Marks, H. L., and P. D. Lepore, 1968. Growth rate inheritance in Japanese quail. 1. The establishment of environmental conditions which restrict juvenile growth rate. Poultry Sci. 47:556-560. Sadjadi, M., and W. A. Becker, 1980. Heritability and genetic correlations of body weight and surgically removed abdominal fat in Coturnix quail. Poultry Sci. 59:1977-1984. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Ed. SAS Inst Inc., Cary, NC. Summers, J. D., S. J. Slinger, and G. C. Ashton, 1965. The effect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poultry Sci. 44:513-520. Washburn, K. W., R. A. Guill, and H. M. Edwards, Jr., 1975. Influence of genetic differences in feed efficiency on carcass composition of young chickens. J. Nutr. 105: 1311-1317. Wilson, W. O., U. K. Abbott, and H. Abplanalp, 1961. Evaluation of Coturnix (Japanese quail) as pilot animal for poultry. Poultry Sci. 40:651-657. Wyatt, J.M.F., P. B. Siegel, and J. H. Cherry, 1982. Phenotypic relationships between adiposity, breast weight, and body weight in female Japanese quail. Poultry Sci. 61:643-646.
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Verstrate, 1979. Prediction of fat and fat free live weight in broiler chickens using backskin fat, abdominal fat, and live body weight. Poultry Sci. 58:835-842. Burke, W. H., and H. L. Marks, 1984. Gonad growth and plasma luteinizing hormone levels in quail {Coturnix coturnix japonica) selected for high four-week body weight Poultry Sci. 63(Suppl. 1):72. (Abstr.) Cartwright, A. L., H. L. Marks, and D. R. Campion, 1988. Adipose cellularity in nonselected and selected broiler stocks: measurements at equal weights and ages. Poultry Sci. 67:1338-1344. Chambers, J. R., J. S. Gavora, and A. Fortin, 1981. Genetic changes in meat-type chickens in the last twenty years. Can. J. Anim. Sci. 61:555-563. Darden, J. R., and H. L. Marks, 1985. The influence of dietary salt on water consumption and carcass lipids in Japanese quail. Poultry Sci. 64:1269-1278. Darden, J. R., and H. L. Marks, 1988. Divergent selectionfor growth in Japanese quail under split and complete nutritional environments. 1. Genetic and correlated responses to selection. Poultry Sci. 67:519—529. Edwards, H. M., Jr., 1981. Carcass composition studies. 3. Influences of age, sex and calorie-protein content of the diet on carcass composition of Japanese quail. Poultry Sci. 60:2506-2512. Frisch, R. E., 1980. Pubertal adipose tissue: is it necessary for normal sexual maturation? Evidence from the rat and human female. Fed. Proc. 39:2395-2400. Goodwin, T. L., L. D. Andrews, and J. E. Webb, 1969. The influence of age, sex, and energy level on tenderness of broilers. Poultry Sci. 48:548-551. Gyles, N. R., A. Maeza, and T. L. Goodwin, 1982. Regression of abdominal fat in broilers and abdominal fat in spent parents. Poultry Sci. 61:1809-1814. Marks, H. L., 1971. Evaluation of growth selected quail lines under different nutritional environments. Poultry Sci.
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