Short Barb: A Feather Structure Mutation in Japanese Quail

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ABSTRACT A type of feather structure abnormality in Japanese quail resulting ... (Key words: Japanese quail, genetics, mutation, feather, recessive, autosomal, ...

BREEDING AND GENETICS Short Barb: A Feather Structure Mutation in Japanese Quail J. E. FULTON,1 C. W. ROBERTS,2 C. R. NICHOLS, and K. M. CHENG3 Avian Genetics Laboratory, Department of Poultry Science, The University of British Columbia, Vancouver, British Columbia V6T 2A2 (Received for publication December 21, 1981) ABSTRACT A type of feather structure abnormality in Japanese quail resulting in shortened barbs on contour feathers was found to be controlled by a single autosomal recessive gene, sb (short barb). The mutation was first identified in a full-sib family from the University of British Columbia wild type line. Unlike other feather structure mutations in Japanese quail reported previously in literature, the short barb mutation is not associated with poor reproduction. (Key words: Japanese quail, genetics, mutation, feather, recessive, autosomal, reproduction, autosomal recessive) 1982 Poultry Science 61:2319-2321 INTRODUCTION During a body weight selection experiment in Japanese quail (Lau and Roberts, unpublished data), chicks with abnormal feathers were observed in 4 of .11 progeny from one breeding pair. The first set of feathers, which replaced down at about 7 days of age, looked ragged and stringy and were subsequently replaced by similar abnormal feathers through successive molts. The abnormality was apparent as the feathers emerged from the sheath. The coloration was that of wild-type (WT) feathers [the experimental birds originated from the University of British Columbia (UBC) WT line (Roberts et al, 1978)] but the structure of the feathers was abnormal. The most obviously affected group of feathers were the contours on the back of the birds. The barbs of these feathers, particularly the distal portion, were short; approximately three-quarters of the length of the barbs on both sides of the feather was missing and the feather had the appearance of being broken off (Fig. 1). The breast feathers and flight feathers were similarly affected but to a lesser degree (leading edge of feather, Fig. 1). The feathers on the legs and sides of the birds also had a stringy look and they, too, had shortened barbs. Because of this particular feature of the feathers, the feather structure abnormality was called "short barb".

1 Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. 2 Deceased January, 1980. 3 Reprint requests.

In recent years there have been several reports of feather abnormalities in Japanese quail. Savage and Collins (1971) reported a downless mutation controlled by two autosomal loci. Roberts and Fulton (1979) found an autosomal recessive mutant with defective barbules that they called rough-textured (rt). Another feather abnormality in quail, the porcupine (pc) (Fulton et al., 1982), is autosomal recessive and leads to failure of the barbs to uncoil. All three of these feather mutations have poor reproduction; downless males are sterile (Savage, personal communication), rough-textured females have low fertility, and porcupine mutants have low fertility and high embryonic mortality. In addition, poor egg production is also associated with all three of these mutations. The purpose of this paper is to report the inheritance of the short barb feather structure mutant in quail. MATERIALS AND METHODS At breeding age there were one mutant male and three mutant females. These birds were each mated to a normal feathered bird from the UBC WT population. The chicks produced by these mating were intermated to produce F 2 progeny. Standard genetic crosses of mutant X WT, mutant X heterozygote, heterozygote X heterozygote, and mutant X mutant were made to determine the inheritance of the short barb trait and to obtain more individuals for the development of the short barb line. Birds of 4 to 5 months of age were used in all genetic crosses to ensure maximum hatchability (Woodard and Abplanalp, 1967). Matings

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FULTON ET AL.

were random except that no full-sib matings were allowed. Eggs were pedigreed, stored for 2 weeks in a cooler (13 C), and then incubated in a modified Jamesway 252 incubator. All chicks were wingbanded at hatch and reared in commercial game chick brooders (Marsh Mfg.). The phenotype of all birds was determined between 24 and 28 days of age when the abnormality was most easily distinguished from wild-type.

RESULTS AND DISCUSSION

Table 1 presents the hatchability of eggs and the phenotypes of chicks produced by each mating type. There are no differences in fertility and hatchability nor in the proportion of mutant chicks produced by reciprocal matings; therefore, data were pooled within mating types. There were no apparent reproductive problems associated with the short barb mutant as fertility for all crosses was over 90% and hatchability ranged from 74 to 89%. These figures are comparable to those from the original WT population. The 23 reciprocal matings of short barb X WT produced 267 wild-type progeny. The sex ratio of 121 males: 129 females (with the sex of 17 individuals not determined) did not deviate significantly from a 1:1 ratio (x 2 = . 13; df = 1; P>.05). Three similar matings produced both mutant and normal chicks in a 1:1 ratio (20 WT:15 short barb). Presumably, the mutant gene was segregating in the base population, and the WT birds used were actually hetero-

zygous for the trait. These three matings were excluded from the data analyses. The progeny produced by the intermatings of heterozygotes did not differ significantly from a 3:1 ratio (200 WT:69 short barb). Sex ratios for both WT progeny (94 males: 106 females) and short barb progeny (36 males: 33 females) were not significantly different from a 1:1 ratio (x 2 = .72 and .13, respectively; df = 1;P>.05). The reciprocal matings of short barb X heterozygotes produced 104 WT and 87 short barb progeny. The observed ratio was not significantly different from a 1:1. The WT progeny fit a 1:1 sex ratio (55 males:49 females; X2 = .35; df = 1, P>.05), but there was a significant deficiency of females in the short barb progeny (55 males: 32 females; X2 = 6.08; df = 1; P.05). Based on these data, the short barb trait appears to be controlled by an autosomal recessive gene. The gene symbol sb is assigned to the locus with Sb+ referring to the wild type allele following Somes' (1980) proposed nomenclature. This feather mutation does not adversely affect reproduction as previously reported feather mutations do. Reproduction of the short barb mutant is comparable to that of the line from which it was derived.

TABLE 1. Reproduction data and progeny ratio in short barb test matings Phenotype 3

Expected ratio 4

Mating type 1

No. of matings

No. of eggs set

% Fertility

% Hatch 2

WT

SB

SBX WT (recipr.)

23

316

95

89

267

0

1:0

Het. X Het.

35

402

96

74

200

69

3:1

0.06NS

SB X Het. (recipr.)

23

255

93

84

104

87

1:1

1.51NS

9

120

96

81

0

93

0:1

SB X SB 1

SB, short barb; WT, wild type; het, heterozygous.

2

Percent hatch of fertile eggs.

3

Phenotype of progeny.

4

Assuming that the short barb trait is single gene recessive.

x2

FEATHER STRUCTURE MUTANT IN QUAIL

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feathers with b r o k e n barbs at sexual m a t u r i t y . Because it can be difficult to distinguish m u t a n t from wild-type birds, it is possible t h a t segregants had occurred in the p o p u l a t i o n previously and had n o t been noticed. The original m u t a n t s were recognized only because they were handled and closely observed during an e x p e r i m e n t .

(Sb/Sb

(sb/sb) Secondary wing feather

(sb/sb) Back contour feathers

FIG. 1. Effect of the sb mutation is most apparent on contour feathers. Barbs of flight feathers from sb/sb individuals are only slightly affected resulting in the appearance of notches on the leading edge.

T h e high frequency of h e t e r o z y g o t e s f o u n d in t h e base p o p u l a t i o n (.12) indicated t h a t t h e frequency of sb in t h e p o p u l a t i o n is rather high (.06). T h e trait c a n n o t be observed clearly until the back feathers have fully emerged ( a b o u t 1 4 to 16 days of age). However, as t h e chicks m a t u r e , distinguishing m u t a n t s from wild-type individuals can be difficult, because the normal wear and tear of feathers causes t h e m t o break. This results in b o t h m u t a n t s and wild-type individuals having ragged, stringy-looking

ACKNOWLEDGMENTS This s t u d y was s u p p o r t e d by a Natural Sciences and Engineering Research Council Canada operating grant and by funds from Agriculture Canada, appropriated b y t h e D e a n ' s Office, F a c u l t y of Agricultural Sciences, for K. M. Cheng. T h e a u t h o r s would like t o t h a n k D. M. Juriloff for reviewing an earlier draft of this manuscript. J a p a n e s e quail genetic stocks at t h e Avian Genetics L a b o r a t o r y are maintained w i t h t h e s u p p o r t of N S E R C C grant A-8467.

REFERENCES Fulton, J. E., C. W. Roberts, and K. M. Cheng, 1982. "Porcupine": A feather structure mutation in Japanese quail. Poultry Sci. 61:429—433. Roberts, C. W., and J. E. Fulton, 1979. Roughtextured: A feather structure mutant of Japanese quail. Can. J. Genet. Cytol. 21:443-448. Roberts, C. W., J. E. Fulton, and C. R. Barnes, 1978. Genetics of white-breasted, white, and brown colors and descriptions of feather patterns in Japanese quail. Can. J. Genet. Cytol. 21:1—8. Savage, T. F., and W. M. Collins, 1971. Downless, a mutant of Japanese quail. Poultry Sci. 50:1627. (Abstr.) Somes, R. G. Jr., 1980. Alphabetical list of the genes of domestic fowl. J. Hered. 71:168-174. Woodard, A. E., and H. Abplanalp, 1967. The effect of mating ratio and age on fertility and hatchability in Japanese quail. Poultry Sci. 46:383 — 388.

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