Francis Minvielle

Background: The Japanese quail (Coturnix japonica) is both an animal model in biology and a commercial bird for egg and meat production. Modern research developments with this bird, however, have been slowed down by the limited information that is available on the genetics of the Japanese quail. Recently, quail genetic maps with microsatellites and AFLP have been produced which open the way to comparative works with the chicken (Gallus gallus), and to QTL detection for a variety of traits. The purpose of this work was to detect for the first time QTL for commercial traits and for more basic characters in an F2 experiment with 434 female quail, and to compare the nature and the position of the detected QTL with those from the first chicken genome scans carried out during the last few years. Results: Genome-wide significant or suggestive QTL were found for clutch length, body weight and feed intake on CJA01, age at first egg and egg number on CJA06, and eggshell weight and residual feed intake on CJA20, with possible pleiotropy for the QTL affecting body weight and feed intake, and egg number and age at first egg. A suggestive QTL was found for tonic immobility on CJA01, and chromosome-wide significant QTL for body temperature were detected on CJA01 and CJA03. Other chromosome-wide significant QTL were found on CJA02, CJA05, CJA09 and CJA14. Parent-of-origin effects were found for QTL for body weight and feed intake on CJA01. Conclusion: Despite its limited length, the first quail microsatellite map was useful to detect new QTL for rarely reported traits, like residual feed intake, and to help establish some correspondence between the QTL for feed intake, body weight and tonic immobility detected in the present work and those reported on GGA01 in the chicken. Further comparative work is now possible in order to better estimate and understand the genetic similarities and differences of these two Phasianidae species.

Background: The genetics of plumage of Japanese quail is of interest both from a biological standpoint, for comparative studies between avian species, and from a zootechnical standpoint, for identifying commercial selection lines or crosses. There are only few plumage mutations reported in quail, and the present work describes a new color variant "rusty" and a new feather structure "curly", and their heredity from an F1 and F2 segregation experiment. Results: Curly feathers result from abnormal early growth caused by transient joining of follicle walls of adjacent feathers around 10 days of age, but the expression of the trait is variable. Rusty plumage color results from the replacement of the wild-type plumage pattern on the tip of the feather by a reddish coloration, but the pigmentation of the bottom part of the feather is not affected. Two lines breeding true for the curly or the rusty phenotype were developed. Both characters are determined by autosomal recessive mutations which are independent. The curly mutation has also a positive effect on body weight at 5 weeks of age. Conclusion: The curly line is a new model which may be used for further work on the growth of the feather, and the rusty mutation is a new addition to the panel of plumage mutations available for comparative studies in poultry, and more generally among avian species.

The interactions between the effects of three plumage color mutations taken two-by-two (sex-linked recessive roux, autosomal recessive lavender, and autosomal dominant beige) were studied in Japanese quail by producing a total of 121 F₁ and 1118 F₂ quail from the three pure stocks. Three new plumage colors were obtained in F₂ quail: roux-diluted beige, cream, and lavender-diluted beige. Two of them, roux-diluted beige (from the roux and beige mutations) and cream (from the roux and lavender mutations) corresponded to double homozygotes or hemizygous birds, and could therefore be used to tag a quail line. On the other hand, an F₃ from F₂ birds with lavender-diluted beige plumage was necessary to show that quail with this plumage color were homozygous for the lavender mutation, but were either homozygous or heterozygous for the beige gene. In all three F₂s, observed segregation of plumage colors fit simple two-locus Mendelian inheritance.

Fearfulness and economic traits were studied in three lines of Japanese quail. Two of the lines were of the same genetic origin and were subjected to divergent selection for the duration of tonic immobility (TI), a measure of fearfulness. Birds were selected for long (LTI) or short (STI) duration of TI. The third line (DD) was of a different genetic origin and had been selected for early egg production. Fear, growth, residual feed intake, and measures of egg composition and production varied among lines. The distribution of TI in Line DD was closer to that from Line STI. Residual feed intake and shell content were lowest in the DD line. The DD birds laid more broken eggs than quail of the other lines. The STI line birds had higher BW and laid more, but smaller, eggs than LTI line birds. Eggs laid by LTI line birds had higher albumen content, but lower percentage shell, than those laid by STI line birds. When all traits were considered together, there was an overall tendency for STI line birds to out perform LTI birds with DD line birds showing intermediate performance. This finding supports the notion that there is a relationship between fearfulness and productivity. However, the skewed distribution of TI precluded estimation of correlation with production traits in the LTI and STI lines. No significant relationships among fear and production-related traits were found in the DD line, which contradicts the notion that fearfulness and production are related.

Homology for two plumage color loci was studied by hybridization between chickens and Japanese quail. First, chicken-quail hybrids were produced from homozygous “lavender” chicken cocks and “bleu” Japanese quail, and all 30 hybrids had the same parental slaty blue plumage color. On the other hand, no hybrids with this plumage were obtained out of 18 progeny from the same cocks and wild-type quail. These results show that the slaty blue plumage color is determined by homologous loci in Japanese quail and chickens. Second, all (n = 25) chicken-quail hybrids hatched from homozygous “recessive white” cocks and “recessive white” (n = 8) or “wild-type” (n = 17) quail had the same pattern of plumage color, with white feathers on the ventral face and colored feathers elsewhere. These results indicate that the recessive white mutations are not homologous in Japanese quail and chickens.

DNA fingerprints of Japanese quail male and female pure line breeders were obtained with probes 33.6, 33.15, and R18.1 and they yielded a total of 59 scoreable bands. Bandsharing (0 < BS < 1) was calculated within and between six quail lines of two origins, and under reciprocal recurrent (AA and BB), within-line (DD and EE) or no (PP and FF) selection. Twenty one pair types were compared. BS was 0.30 higher within line than between lines. BS with the control line was smaller for reciprocal recurrent selection lines than for lines under individual selection. Bandsharing between the two reciprocal recurrent selection lines was 0.19 lower than between lines under individual selection. These results indicate that the two selection methods had different effects on the genetic constitution of the lines, in agreement with previous observations made from the analysis of biochemical polymorphisms with the same set of birds. Egg production and weight traits of pure and crossbred progeny from fingerprinted quail were obtained and compared, and a linear relationship with the measure of bandsharing was estimated. No significant regression coefficient of performance on BS was found over all progeny genetic types. Heterosis from individual matings could also be estimated under the two selection methods since the same birds were parents of both pure and crossbred performance-tested quail. The association of heterosis with the difference between BS of parents of the purebreds and BS of parents of their half-sib crossbreds was favourable and significant for early production traits in lines DD and EE, but no relationship was found in lines AA and BB. These results indicate that the high level of heterosis obtained through reciprocal recurrent selection, and the heterosis observed under within-line selection may have, partly at least, a different genetic determinism. Therefore, the relationship of heterosis with BS may also depend on the past history of selection in the lines.

1. The roux plumage sex-linked recessive gene may be used for early sexing of Japanese quail in crossbreeding production systems with wild-type and roux lines. However, associated effects of the gene on carcase and meat composition need to be assessed. 2. Quail carcases from pure Line K males and females (100% K), a heavy meat line which was used as the recipient line for the introgression of the roux gene, and from same-age roux or wild-type females from the second generation of introgression (75% K) were dissected. The effects of sex, line and plumage colour on carcase components and on protein and lipid contents of various tissues were estimated. 3. Expected sex differences in carcase weights were obtained, with marginally higher values for females. However, weights of parts and carcase yield (ratio of empty carcase weight without head, neck and feet over live body weight) were similar for both sexes in pure Line K which had a 68% carcase yield. Lipid contents in leg meat were higher in males (3.1%) than in females (2.7%). 4. The roux gene did not seem to have any major impact on carcase parts or composition. However, in roux birds, leg skin was marginally higher in lipids and pectoralis major lower in proteins than in wild-type ones.

After two generations of introgression of the sex-linked recessive roux color mutation into a commercial broiler Japanese quail line with wild-type plumage, growth, carcass, egg laying, and reproduction of birds were evaluated and compared for all types of birds produced (considering sex, line, and plumage). Usual sex differences were obtained for BW, with larger values in females and 5% sexual dimorphism. Weights were larger also in the pure commercial line, which had a higher hatching rate (HR) than the introgressed birds at 17 to 19 wk of age. Roux plumage was significantly associated with 3% lower BW and 30% less abdominal fat (AF) pad. Egg production was not influenced by the roux mutation, but egg weight (EW) was 2% lower. Characteristics associated with the roux gene are similar to those reported for the albino mutation, except for AF, which was not tested in albino quail. The similarity of the pleiotropic effects might result from some modification that the two mutations induce in an early step of a metabolic pathway involved both in coloration and in growth. From a practical breeding standpoint, the roux gene appears to be a interesting candidate gene for auto-sexing in quail production.

At Generations 15 (males) and 18 (females) of a divergent selection experiment on residual feed consumption (RFC) in laying poultry, patterns of growth, feed consumption, and associated traits were monitored between the ages of 4 and 34 wk. This monitoring was done to determine how the well-established RFC and feed intake (FI) divergences between adults of the low intake R- line and of the high intake R+ line took place, in relation to the evolution of correlated traits. In males and females, BW and BW gain were higher in the R- line in the first weeks of test, but patterns of BW were quite similar in both lines afterwards. However, R- hens remained heavier than R+ females to the end of the experiment. Line difference for BW was achieved by 28 wk of age, at 2,974 and 2,094 g, and the R- line was then 135 and 133 g heavier, respectively, for males and females. After a fast initial increase in both sexes, FI diverged quickly around 16 to 18 wk of age (sexual maturity), to attain 13 g/d in males and 28 g/d in females, well before the end of the experiment. At the same time, a divergence was observed for wattle length, which was 21% higher in R+ females. Residual feed consumption gradually diverged in the two lines, and the difference became significant at 14 wk of age. At the same age, shanks were 8% longer in R+ hens. Finally, levels of triiodothyronine decreased faster in the R- line, as FI divergence was increasing. These results indicate that the RFC difference between R- and R+, lines obtained in adult birds by divergent selection lines, starts somewhat early in life. In addition, the RFC difference appears to be associated with specific growth periods, around 14 wk and 18 to 20 wk. It is at this time that large differences appear in morphological traits involved in body heat loss. No significant correlations were found between early (6 wk) measures of FI, feed efficiency, and RFC, with adult values (32 to 34 wk) for RFC and FI.