Correlations between Growth and Reproductive Traits in the Japanese Quail1

Correlations Between Growth and Reproductive Traits in the Japanese Quail 1 H. M. EL-IBIARY,2 E. F. GODFREY AND C. S. SHAFFNER Department of Poultry Science, University of Maryland, College Park, Maryland (Received for publication September 7, 1965)

INTRODUCTION

R

MATERIALS AND METHODS

Two strains of Japanese quail were procured in early 1964. They consisted of 78 chicks obtained as hatching eggs from the U.S.D.A. Research Center at Beltsville, 1

Scientific Article No. A1222. Contribution No. 3727 of the Maryland Agricultural Experiment Station (Department of Poultry Science). Supported in part by Public Health Service Grant AM-08176-01 from the National Institute of Arthritis and Metabolic Diseases. "Present address: Faculty of Agriculture, Camp Cesar P.O., Alexandria, U.A.R.

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ECENTLY, the Japanese quail (Coturnix coturnix japonica) has been introduced to the avian scientist as a pilot animal, and its merits as such were appraised by a number of workers (Padgett and Ivey, 1959; Wilson et al, 1959; and Howes and Ivey, 1961). One outstanding feature of these birds is the short generation interval which makes them particularly ideal for the poultry geneticist. Yet, very limited genetic information on this subspecies is available. In problems dealing with selection in poultry, the breeder is interested in the amount of variation in the different traits, as well as the extent to which growth and reproduction are correlated. Reproductive rates largely govern the degree of change possible under artificial or natural selection. These correlations are therefore of interest to workers in the field of experimental evolution. The present study is a preliminary trial to partially fill this gap on the phenotypic level.

Md. and 29 chicks from the University of Alabama, Auburn. On February 4, 1964, random pair-matings were made between the two strains. Three non-pedigree hatches of the first parental generation (hereafter, designated Pi) were secured on March 3, 17, and 31. The respective number of chicks were 81, 114, and 116. When they were about five weeks old, the prospective parents were randomly chosen, and pairmated on April 10. On July 31, one hatch of 597 chicks was secured from this second generation (hereafter designated Fi). In both generations, the eggs were set in a forced draft incubator which was operated at a temperature of 37.5°C, and about 56% relative humidity. The hatcher, to which they were transferred on the 14th day of incubation, had about 64.5% relative humidity. All eggs were candled on 14th day. Fertility was estimated as percent of fertile eggs, and hatchability as the number of chicks from fertile eggs. The chicks were brooded in batteries at a starting temperature of 35°C. No more than 40 chicks were started in each 70 X 90 cm. deck, or a minimum of 157.5 cm.2 per chick. They were ad libitum fed a 26% protein mash. The batteries were in an air conditioned room and temperatures did not exceed 27°C. In the same room the breeders were housed in 18 X 18 cm.2 cages (one pair per cage) with a sloping floor for collecting the eggs. They were fed ad lib. a 20% protein mash. Chicks and adults were kept on a constant 14 hour lighting schedule. Individual hen records for fertility and hatchability were recorded for the Pi

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H. M. EL-IBIAEY, E. F. GODFREY AND C. S. SHAFFNER TABLE 1.—Effect

of age and sex on variability of growth traits Sign, of

Females

Males Age

1 week 2 weeks 3 weeks 4 weeks 5 weeks 6 weeks 100 days Adult 1

1

weeks weeks weeks weeks weeks weeks

Mean

62 86 85 86 86 86 60 138

14.5 26.8 47.6 67.1 85.6 100.0 111.1 117.6

62 85 84 85 86 63

56.8 56.S 35.6 24.5 16.0 87.0

Mean

% c.v.

difference

1. Body weights in grams: 56 21.9 76 24.4 76 21.7 76 17.9 77 13.2 76 9.8 52 11.5 123 9.6

14.2 26.4 48.0 69.5 89.0 106.4 130.4 143.3

19.9 26.4 24.2 18.4 12.7 11.2 9.7 11.3

>0.05 >0.05 >0.05 >0.05 >0.05 <0.01 <0.01 <0.01

2. Percent growth rates: 31.2 57 17.5 76 28.8 77 29.7 78 43.6 77 17.4 51

56.5 58.3 37.8 25.5 17.9 91.7

35.4 18.6 26.8 32.4 32.7 14.3

>0.05 >0.05 >0.05 >0.05 <0.05 >0.05

% c.v.

N

These data are for Pi generation weighed at 114 days. All other data apply to the Fi generation.

group. Adult body weight was the only growth trait recorded from this generation. The Fi chicks were weighed at weekly intervals for the first six weeks, and again at 100 days of age. The F± percentage growth rates were estimated by Brody's (194S) formula. From both generations, age at first egg, the number of eggs laid to 100 days of age, and the average weight of eggs laid from 97 to 100 days of age were re-_ corded. All percentages were transformed to their corresponding angles for statistical analysis. Whenever the hatch effects were significant these effects were removed before estimating the coefficients of correlation. Coefficients of partial correlation were estimated between certain pairs of characters. Statistical significance of all correlations were determined by use of appropriate mathematical tables (Snedecor, 1956). RESULTS AND DISCUSSION

The females were consistently heavier than the males at all ages, but the differences were not significant before the sixth week of age (Table 1). The sex difference steadily increased from 6% at six

weeks to approximately 22% at adult body weight. This is almost comparable, though in the opposite direction, to the sex difference in adult White Leghorns. Stevens (1958) reported consistently lighter body weights in females than in males during the first forty days. At 43 days of age the females became heavier by about 6%, and at 90 days this difference increased to 11%. In contrast variability of body weight followed an opposite trend. While the six week old weight was about seven times that of the first week, its variability decreased almost 50%. Both sexes had almost equal coefficients of variation for body weight at all ages studied. The percentage growth rates were highest in both sexes between the first and third weeks of age (56.5%-58.3%), and decreased sharply to less than one third at 5-6 weeks (16.0%-17.9%). The sex difference in relative growth rate became significant at 5-6 weeks. Generally speaking the percentage growth rates were more variable than body weights up to six weeks of age. The coefficient of variation of the former trait had two peaks, the first at 1-2 weeks, and the second at 5-6 weeks.

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1-2 2-3 3-4 4-5 5-6 2-4

N

GROWTH AND REPRODUCTION OF QUAIL

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T A B L E 2 . — V a r i a b i l i t y of reproductive traits of These data indicate that in selecting for female Coturnix quail fast growth in the Japanese quail, the most appropriate criterion for selection would be Genera% Mean Traits tion C.V. the percentage growth rate from one to two 137 20.4 Age a t sexual maturity (days) Pi 48.8 weeks of age. This period not only repre52 11.0 53.2 Fi sents one of two peaks at which the varia- Egg number to 100 days of age Pi 118 45.7 21.6 41.7 23.6 Fi 52 bility rises to a maximum, but it also has Egg weight (grams) 100 10.1 7.0 Pi the advantage of earliness. Another good 43 9.4 6.8 Fi criterion may be the percentage growth Percent fertility 46.2 Pi 75.7 rate from 2-4 weeks of age. This has less Percent hatchability 37.4 63.6 Pi variation than the first proposed criterion, but includes both the high level of growth land experimental birds. In general, it rate at 2-3 weeks of age, which is compara- seems that the Japanese quail is reproducble to that of the first two weeks, and the tively inferior to the modern domestic fowl. drop in growth rate from 3-4 weeks of age To what extent the observed inferiority (Table 1). was due to differences in the mating system The means and coefficients of variation and/or age cannot be decided upon from of the five reproductive traits are shown in the data in hand. These observations were Table 2. The Pi females reached sexual made on pair-mated birds in their first maturity at an earlier age, and produced breeding season. The recorded maximum more and larger eggs than those of the Ft. life span for Coturnix coturnix in captivity The differences in these three characters is ten years (Altman and Dittmer, 1962). were statistically significant. It is possible Among the growth and reproductive that the differences were due to seasonal traits studied, fertility and hatchability effects, but since the Pi was a strain-cross, had the highest coefficients of variation. the possibility that the differences were due Egg weight was the only reproductive trait to heterosis should not be overlooked. with lower percent variability than growth The two experimental generations did traits. The variations in the age at sexual not materially differ in the age at sexual maturity, and number of eggs laid were maturity from the means reported by Pad- within the range of those of growth traits. gett and Ivey (1959) and Wilson et al. The Japanese quail was recently intro(1961). Yamashina (1961) reported a duced to this country as a game bird. In wider range in the commercial quail flocks spite of several attempts, introductions in Japan (35-60 days). In the two experi- have not been successful (Mathison and mental generations, there was a difference Mathison, 1960). The present data indiof four eggs, which reflected a cate that its adjustment to a new habitat is 5.6-day difference in sexual maturity, but reflected in the relatively high variations in both generations laid at the same rate fertility and hatchability which are the (0.89 egg/day). The egg weight, 100-day traits most related to fitness among the body weight ratio of both generations was characters studied. similar, averaging approximately seven perHatch effects were studied for the three cent. This is more than twice the corre- Pi hatches (Table 3). Among the six charsponding ratio for White Leghorns. Wil- acters listed in this Table, age at sexual son et al. (1961) reported a similar ratio. maturity, and number of eggs to 100 days The same authors reported lower fertility of age were the only two which were affectand hatchability than noted for the Mary- ed by the date of hatch. A shorter hatching

466

H. M. EL-IBIARY, E. F. GODFREY AND C. S. SHAFFNER TABLE 3.—Between hatch effects on reproductive traits and adult body weight (Data from Fi) 3/3

Date of Hatch (1964) Traits Age at sexual maturity (days) Egg number to 100 days of age Egg weight (grams) Percent fertility Percent hatchability Adult body weight (grams): males females

3/16

3/31

Significance - of difference P Mean

N

Mean

N

Mean

N

35 32 31 30 24

52.2 41.4 10.2 73.4 63.1

54 46 42 42 38

46.3 48.5 10.1 76.3 66.8

48 40 27 27 24

49.0 45.8 10.0 77.4 58.9

<0.05 <0.01 >0.05 >0.05 >0.05

36 32

119.7 144.6

52 46

116.8 145.2

50 45

117.5 140.6

>0.05 >0.05

TABLE 4.—Estimates of the coefficients of correlation between growth and reproductive traits of the female coturnix quail (Y) Growth traits Body weight

(X) Reproductive traits 1

Adult (P0 N Age at sexual maturity Number of eggs to 100 days Egg weight Fertility Hatchability

r

120 •- . 2 2 3 * 117 .344** 99 .465** 98 .054 85 .044

% Growth rate (Fi) 2-3 wk

100 days ( F , ) N

r

N

52 51 43 52 52

.137 .136 .188 - .029t - ,049f

55 51 42 55 55

r .078 .024 - .196 .037f .049f

3-4 wk. N

r

55 51 42 55 55

.294* .089 .040 .072f .122t

1 Unless otherwise stated, all X's were from the same generation specified in the Y-columns. * Significant at 0.05 level. ** Significant at 0.01 level.

ttXp,

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growth rate at 2-3, or 3-4 weeks (Table 5). This was also true when the partial correlation between them was estimated independent of age at sexual maturity. In general, it may be concluded that in the Japanese quail, age at sexual maturity is, to a certain extent, negatively correlated with adult body weight, but positively correlated with 3-4 week percent growth rate. The coefficient of correlation between the number of eggs to 100 days of age, and adult body weight was 0.344. Although this correlation is not well established in chickens, a number of workers (reviewed by Jull, 1952) have reported estimates of about the same value but with a negative sign. It will be recalled that egg number up to 100 days of age confounds age at sexual maturity. Even though, when the latter

season, or statistical corrections for hatch effects would be appropriate if such environmental sources of variations are to be avoided in breeding studies using the Japanese quail. The correlations in Table 4 show that, in contrast to chickens, the age at sexual maturity in Pi was negatively correlated with adult body weight, yet, the coefficient (—0.223) was as low as in chickens. In F a birds, the age at sexual maturity was positively correlated with 3-4 week percent growth rate, and the coefficient of correlation was also small (0.294). In the same generation, a significant and almost equal partial coefficient (0.281) was estimated between the same two characters independent of body weight. Body weight at 100 days of age was not correlated with percent

467

GROWTH AND REPRODUCTION OF QUAIL

TABLE T S.—Estimates of the coefficients of correlation between pairs of reproductive traits and pairs of growth traits Generation

N

r

Pi Fi

118 52

-.643** -.600**

Sexual maturity & egg weight

Pi Fi

100 43

-.033 -.003

Sexual maturity & fertility

PI

99

-.155

Sexual maturity & hatchability

PI

86

.130

Egg number & egg weight

PI FI

98 43

-.053 .080

Egg number & fertility

Pi

97

-.070

Egg number & hatchability

Pi

84

.089

Egg weight & fertility

Pi

97

.180

Egg weight & hatchability

Pi

84

-.149

Pairs of Traits 1. Reproductive: Sexual maturity & egg number

Fertility & hatchability

Pi

86

.035

2. Growth: 100-day body weight & 2-3 wk. % growth rate

Fi

51

.061

100-day body weight & 3-4 wk. % growth rate

Fi

51

.140

2-3 wk. & 3-4 wk. % growth rates

Fi

55

.041

** Significant at 0.01 level.

to be unaffected by the variation in adult, or 100-day body weight, or in egg number as the partial coefficients in both cases were insignificant and low. In conclusion, among the five studied reproductive traits, age at sexual maturity, number of eggs to 100 days of age, and egg weight were probably the only ones correlated with adult body weight. The only reproductive character which may have been correlated with early growth was sexual maturity. Although the coefficients of correlation were statistically significant in all these cases, they all had values of less than 0.5. In selection for early growth rate, or adult body weight in the Japanses quail, it seems advisable to watch for possible changes in these three reproductive traits. Most likely, fertility and hatchability will not be affected by such selection programs. This discussion seems incomplete without mention of a few points on the foregoing comparisons between the Japanese

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variable was made constant, the partial correlation between egg number and adult body weight did not materially change as a significant coefficient of 0.269 was estimated. Confounding the age at sexual maturity in the quail egg record had a more conspicious effect on the estimated coefficients of correlation between these two traits. The estimates which were highly significant were —0.643 and —0.600 in Pi and Fi, respectively (Table 5). Body weight at the later ages did not seem to affect this correlation. Independent of adult, or 100day body weights, the respective estimates of partial correlations were —0.618 and — 0.631, and both were also highly significant. Although in most chicken flocks this correlation has values between —0.20 and — 0.50, the similarity between them and the quail is obvious. In the Pi, the estimated coefficient of correlation between egg weight and adult body weight (Table 4) was highly significant. This is also generally true with chicken data. Independent of the age at sexual maturity, a highly significant partial coefficient of 0.470 was estimated between the same two traits. In both generations, egg number and egg size seemed unrelated (Table S). In chickens, the estimates of this correlation are quite variable, but usually low. In the quail data reported the partial coefficient between egg number and size was —0.256. This is independent of adult body weight. But in contrast to adult body weight, the age at sexual maturity did not seem to affect the correlation between egg number and size as the partial coefficient was insignificant and low ( — 0.097). In both generations, it seemed also that egg weight and age at sexual maturity were unrelated (Table 5). In this respect, the chicken and the quail seem to be similar. In the experimental quail, this lack of correlation seems

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H. M. EL-IBIARY, E. F. GODFREY AND C. S. SHAFFNER

SUMMARY

The means, coefficients of variations and simple and partial correlations were estimated for body weight, relative growth rate, and five reproductive traits in two successive and random-bred generations of the Japanese quail. Among all traits studied, fertility and hatchability had the highest coefficients of variation (0.46 and 0.37, respectively), and egg weight had the lowest (about 0.07). The variations in body weight, relative growth rates, age at sexual maturity and egg number were within the percentage range of .07 to .46. Statistically significant sex differences were found for 6-week body weight, and 5-6 week growth rate. Significant hatch effects were noted for sexual maturity and egg number.

While age at sexual maturity was negatively correlated with adult body weight, it was positively correlated with 3-4 week percent growth rate. Both coefficients were significant but low (—0.223, and 0.294, respectively). Other significant, but relatively higher estimates were found between egg number, and adult body weight (0.344); egg number and sexual maturity ( — 0.643 in Pi and —0.600 in Fx); and between egg weight and adult body weight (0.465). Egg number and egg size seemed to be unrelated, but independent of body weight, a significant partial coefficient of —0.256 having been estimated for the first generation. The bearings of these findings on the breeding and adaptation of the Japanese quail were compared to the domestic fowl. Some of the possible errors inherent in this comparison were suggested. REFERENCES Altaian, P. L., and D. S. Dittmer, 1962. Growth Including Reproduction and Morphological Development. Fed. Amer. Soc. for Exp. Biology, Washington, D.C. Brody, S., 1945. Bioenergetics and Growth. Reinhold Pub. Co. Corp., New York. Howes, J. R., and W. D. Ivey, 1961. Coturnix quail for avian research. Feedstuff, 33(21): 38-39. Jull, M. A., 1952. Poultry Breeding. J. Wiley and Sons, New York. Mathison, J. E., and A. Mathison, 1960. History and status of introduced game birds in Nebraska. Nebraska Bird Rev. 28: 19-22. Padgett, C. A., and W. D. Ivey, 1959. Coturnix quail as a laboratory research animal. Science, 129: 267-268.

Snedecor, G. W., 1956 Statistical Methods. Iowa State Univ. Press. Stevens, V. C , 1958. Observations on the reproduction and development of the Coturnix quail. M.S. Thesis, Ohio State Univ. Wilson, W. O., U. K. Abbott and H. Abplanalp, 1959. Developmental and physiological studies with a new pilot animal for poultry—Coturnix quail. Poultry Sci. 38: 1260-1261. Wilson, W. O., U. K. Abbott and H. Abplanalp,

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quail and the chicken. The need for a chicken-control in this study was overruled from the very beginning. The obvious reason was the wide differences between the quail and chicken, particularly in the length of generation interval, and its component traits. Instead, it was decided to compare the results sought on the quail with the literature on the chicken, and indeed there was enough of the latter. Even so, two main differences between these two phasianidae have to be kept in mind. While the chickens have been subjected to all sorts of selection, Japanese quail have not. The second point is the pronounced migratory instinct of the quail which is totally absent in the chicken. It has been observed that this behavioral difference might affect production and reproduction in the quail. Although no quantitative observations were recorded, extreme nervousness has been noted in fall and late spring. Another source of error in these comparisons might have been caused by estimating the quantitative traits in the quail by the same conventional scales used in the chicken.

GROWTH AND REPRODUCTION OF QUAIL 1961. Evaluation of Coturnix (Japanese quail) as a pilot animal for poultry. Poultry Sci. 40: 651-657.

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Yamashina, Y., 1961. Quail breeding in Japan. J. Bombay Nat. Hist. Soc, 58: 216-222 (Abstract No. 732, A.B.A., 3 1 : 124, 1963).

Identification of Sex of Day-Old Quail {Coturnix coturnix japonica) by Cloacal Examination1 KAZUTAKA HOMMA,2 THOMAS D. SIOPES, WILBOR O. WILSON

(Received for publication September 16, 1965)

E

ARLY determination of the sex of Japanese quail (Coturnix coturnix japonica) is desirable when these birds are raised for experimental purposes. Sexual dimorphism does not become obvious until the contour feathers emerge when the quail are 2 to 3 weeks of age. The birds usually are sexed by the difference in color of the breast feathers, the male having brownishred feathers and the female characteristically having tan (gray) feathers with black speckles. In some mutant stocks, color of the feathers remains identical in both sexes even after sexual maturity, e.g., the "ghost bar mutant" and other types of albinos. In these stocks, identification of the sex is possible by observing the development of the cloacal gland after the birds were 4 weeks of age. This gland is located in the dorsal wall of the cloaca and becomes hypertrophic in sexually active males. The above two methods are not satisfactory for experiments where one sex is preferred, and a very early initiation of experimental procedure is desired. A saving in Supported in part by USPHS research grant NB 04171 from the National Institute of Neurological Diseases and Blindness. 2 Present address: Department of Animal Physiology, Faculty of Agriculture, Nagoya University, Nagoya, Japan.

time and expense may be achieved by sexing day-old birds. Two methods of sexing day-old chickens have been used. One is the use of color marker genes for autosexing. The other method involves examination of the cloaca or vent. A preliminary trial of this latter method for sexing day-old quail has been reported in Japan as part of a general textbook of chick sexing (Maeta, 19S0). The present paper describes a practical method of sexing day-old quail by cloacal examination and gives data relative to variations in their genital structures and sex ratio. Although day-old coturnix quail weigh less than 8 g. and the diameter of the cloacal opening is less than 3 mm., the accuracy of sexing quail by cloacal examination is comparable to or better than that reported for day-old chickens. MATERIALS AND METHODS

1. Equipment—Initially we used for examination either a binocular dissecting microscope (American Optical to 20 X) or a Luxolamp with 2 X magnification and utilizing a 22 watt ring-shaped fluorescent light. After a little practice we no longer needed magnification for sexing "typical" males or females. By adjusting the direction of illumination, the reflection of light from the mucosal surface or from the sur-

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AND LARRY Z. MCFARLAND Department of Poultry Husbandry and Anatomy, University of California, Davis