A. Bordas

An uncoupling protein homologue putatively involved in facultative muscle thermogenesis in birds

The cDNA of an uncoupling protein (UCP) homologue was obtained by screening a chicken skeletal-muscle library. The predicted 307-amino-acid sequence of avian UCP (avUCP) is 55, 70, 70 and 46% identical with mammalian UCP1, UCP2 and UCP3 and plant UCP respectively. avUCP mRNA expression is restricted to skeletal muscle and its abundance was increased 1.3-fold in a chicken line showing diet-induced thermogenesis, and 3.6- and 2.6-fold in cold-acclimated and glucagon-treated ducklings developing muscle non-shivering thermogenesis respectively. The present data support the implication of avUCP in avian energy expenditure.

Effect of the slow (K) or rapid (k+) feathering gene on body and feather growth and fatness according to ambient temperature in a Leghorn × brown egg type cross

Chicks of both sexes issued from the cross of heterozygous K/k+ cocks for the slow-feathering sex linked K allele with k+ (rapid feathering) hens, were compared from the age of 4 to 10 weeks at two ambient temperatures. In individual cages, 30 male chicks of each genotype (K/k+ and k+/k+) were raised at 21°C, and 60 others, distributed in the same way, were raised at 31°C. 71 K/W females and 69 k+/W females were raised in a floor pen at 31°C till 10 weeks of age. In the males, the body weight, feed consumption and feed efficiency at different ages were influenced only by temperature (lower growth rate and feed intake at 31°C); no significant effects of the genotype at locus K nor genotype × temperature interaction were observed. In females, all at 31°C, the genotype (K/W or k+/W) had no significant effect on growth rate. Plumage weight and weight of abdominal fat (absolute or related to body weight) were measured on half of the males of each group in individual cages, at 10 weeks of age. Moreover, on 36 males and 48 females of the two genotypes, in a group battery at 31°C, the absolute and relative weight of plumage were measured on a sample every two weeks between 4 and 10 weeks. In the first case, no significant effect of genotype appeared. In the second case, an interaction between age and genotype was suggested from plumage weight: its growth, especially in male chicks, appears to be temporarily and unexpectedly faster from 4 to 6 weeks of age for the K/k+ and K/W genotypes.

Hepatic lipogenesis gene expression in two experimental egg-laying lines divergently selected on residual food consumption.

Two Rhode Island Red egg-laying lines have been divergently selected on residual food intake (low intake R- line, high intake R+ line) for 19 generations. In addition to direct response, correlated responses have altered several other traits such as carcass adiposity and lipid contents of several tissues, the R+ animals being leaner than the R- ones. In a search for the biological origin of the differences observed in fat deposit, the hepatic mRNA amounts of genes involved in lipid metabolism were investigated. No difference was found between lines for mRNA levels of ATP citrate-lyase, acetyl-CoA carboxylase, fatty acid synthase, malic enzyme and CCAAT/enhancer binding protein α, a transcription factor acting on several lipogenesis genes. The genes coding for stearoyl-CoA desaturase and apolipoprotein A1 displayed significantly lower mRNA levels in the R+ cockerels compared to the R-. All together these mRNA levels explained 40% of the overall variability of abdominal adipose tissue weight, suggesting an important role of both genes in the fatness variability.

Effect of Introducing the Naked Neck Gene in a Line Selected for Low Residual Feed Consumption on Performance in Temperate or Subtropical Environments

The aim of this study was to investigate the possibility of combining the naked neck gene with a genetic background that has been optimized for feed efficiency of laying hens at moderate temperature. In 1997, the naked neck gene was introduced into a line selected for low residual feed intake. In 2003, after 6 generations of introgression, 8 males and 56 females heterozygous for the NA*NA mutation were used to generate all 3 genotypes (NA*N/NA*N, NA*NA/NA*N, NA*NA/NA*NA), in 2 hatches, for rearing in Taiwan and France, respectively, at 3-wk intervals. Growth performance, anatomical traits, laying traits, and feed efficiency were recorded in each country. In addition, comb and rectal temperatures were measured in Taiwan. Performance was generally lower and mortality of laying hens was higher in Taiwan (11%) than in France (1%). Genotype x environment interactions were rare: genotype x environment was observed only for body weight at 10 wk of age and was close to significance for egg weight. The laying performance was significantly decreased in Taiwan by about 25%. The naked neck genotype had a negative effect on body weight and a positive effect of clutch length and egg weight. It also affected heat dissipation traits such as wattle length and rectal and surface temperature measurements. There was a clear additive and negative effect of the NA*NA mutation on rectal temperature. Feed intake and residual feed intake were increased in the homozygous carriers of the NA*NA mutation, which may improve heat tolerance of the low residual feed consumption (R-) line. Feed efficiency tended to be better in NA*NA/NA*NA hens in both environments. Thus, the introduction of the NA*NA mutation in the R- background appeared to be favorable from the viewpoint of feed efficiency, but it did not improve laying performance in a subtropical environment. Other factors than temperature, such as diet composition and lighting regimen, may be involved.

Caractéristiques de croissance, ponte et efficacité alimentaire associées au gène Sal(albinos lié au sexe) chez la poule domestique

Les performances de croissance, de ponte et l’efficacité alimentaire de poules albinos (gène sa’ lié au sexe) ont été comparées à celles de leurs soeurs ou demi-soeurs pigmentées : S (plumage « argenté ») dans une première expérience en 1982 ; s+ (plumage a doré ») dans une seconde série en 1983. Par rapport aux types pigmentés, le type albinos s’accompagne d’une croissance, d’un poids corporel adulte, d’un poids moyen de l’œuf et d’une consommation alimentaire un peu inférieurs, et d’une maturité sexuelle retardée de quelques jours. La consommation alimentaire « résiduelle » ne diffère pas pour les poules albinos et non albinos. Le nombre d’oeufs, la masse d’oeufs produite en 28 jours et le pourcentage d’oeufs cassés ne sont significativement modifiés au détriment du gène sal que dans l’une des 2 comparaisons, de même que l’indice de consommation pour la ponte. Les résultats sont rapprochés de ceux obtenus antérieurement pour des gènes supprimant la pigmentation du plumage chez la poule, et pour le gène albinos lié au sexe chez la caille japonaise.

Increase of egg weight with age in normal and dwarf, purebred and crossbred laying hens

Summary - An exponential curve, W = P - Q exp (-Rt) was fitted to egg weights (W) of individual hens from 8 genetic groups tested for egg production from 18-51 weeks of age (t). The groups were constituted of the combination of genotype at the sex-linked dwarfism locus (normal or dwarf) and line (White Leghorn, Brown Egg and both reciprocal crosses). The least-squares mean of the residual standard deviation about the curve was between 1.27 and 1.74 g in the 8 groups and estimated values of the initial P-Q and mature egg P weights were between 26.9 and 33.9 g and 56.9 and 65.8 g, respectively. Effects of genotype and line as well as heterosis were estimated for both egg weights and for rate of growth relative to the remaining expected growth (R). R was smaller for dwarf hens which thus reached mature egg weight later than normal females. Significant heterosis was found for both egg weights of dwarf hens (12.6 and 9.5%) and for the initial egg weight of normal ones (12.8%). Negative heterosis for R obtained for dwarf hens (-17.4%) corresponded to a flatter egg weight curve of these crossbreds.

Gènes a effet visible et coloration ou épaisseur des coquilles d'œufs

Parmi 12 loci étudiés dans une population, deux, concernant la coloration du plumage, présentent une association avec l’épaisseur et la pigmentation externe des coquilles d’œufs : les poules à plumage entièrement noir comparées à celles à noir restreint (locus E) et les poules colorées (ii) comparées à celles où le noir est absent du plumage (Ii) pondent des ceufs à coquille significativement plus épaisse et de teinte plus foncée. Une tendance analogue mais moins marquée semble exister, quant à l’épaisseur des coquilles, pour deux autres loci (C et S) de pigmentation du plumage.

Distributions de fréquences; interprétation du déterminisme génétique desècaract res quantitatifs et recherche de gènes « majeurs »: données expérimentales

La présence de gènes à effet important a été recherchée dans plusieurs populations pedigree de volailles deJouy-en-Josas et de la Station du Magneraud, et pour divers caractères quantitatifs dont la distribution sur l’ensemble de chaque population étudiée ne s’écarte pas considérablement de la normalité : poids corporel, ponte, caractères des oeufs, poids d’organes. Un test proposé antérieurement (MÉ RAT , 1968) est utilisé : examen de la forme (symétrie, kurtosis) des distributions des écarts aux moyennes de familles séparément parmi les familles à plus grande et à plus petite variance observée, lorsqu’une hétérogénéité de ces variances intra-familles a été préalablement mise en évidence. Dans une forte proportion des cas, les variances intra-familles sont très significativement hétérogènes. D’autre part, la distribution des écarts aux moyennes de familles est assez souvent non-normale pour les familles à grande variance, et pratiquement jamais pour les autres, dans les limites de sensibilité du test. Les écarts à zéro des coefficients de symétrie et de kurtosis sont plus fréquemment significatifs et plus extrêmes dans le groupe des a grandes variances »; en outre, les coefficients de kurtosis sont, pour leur majorité, négatifs. L’ensemble de ces résultats suggère l’existence, pour une porportion notable des cas, d’un nombre limité de gènes ou régions chromosomiques rendant compte d’une part importante de la variance génétique totale. Ils sont donc un encouragement à poursuivre cette recherche.

Gènes influant sur la variance phénotypique de l'âge au premier œuf et la composition de cette variance chez la poule domestique

Pour l’âge à la ponte du premier œuf des poulettes, une différence hautement significative de la variance a été trouvée, entre hétérozygotes et homozygotes récessifs, à trois loci : E (extension /restriction du noir dans le plumage), C (présence /absence de mélanines dans le plumage), R (crête en rose /simple). Les hétérozygotes pour le noir étendu, ou pour la présence de coloration, et les homozygotes pour la crête simple, ont un âge à maturité sexuelle moins variable, respectivement, que les poules à noir restreint, à « blanc récessif a ou à crête en rose. Dans ces trois cas, les moyennes ne diffèrent pas, et le génotype ayant la plus grande variance phénotypique s’accompagne d’une composante « père t de la variance proportionnellement plus élevée. Aux loci R et C, la comparaison des croisements réciproques suggère un effet maternel sur la variance de l’âge au le! oeuf.