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The chicken insulin-like growth factor (IGF)1 and IGF2 genes have been partially sequenced in six individuals of each of two chicken strains of the Black Penedesenca breed (PN and MN). These two strains are genetically diverse for growth traits. Sequence alignment revealed the existence of three single nucleotide polymorphisms (SNP) (IGF1-SNP1, IGF2-SNP2, and IGF2-SNP3). These three SNP and a fourth IGF1 polymorphism (IGF1-SNP4) were typed in 60 individuals from each strain by using PCR-RFLP or primer extension analysis. No significant associations among these four SNP, growth traits, and plasma IGF1 concentration were identified. In contrast, suggestive associations (P < or = 0.05) were found between IGF1-SNP1 and average daily gain at 107 d and feed efficiency at 44, 73, and 107 d. However, these associations were not simultaneously found in both strains suggesting that they might have been produced by linkage disequilibrium with another mutation located in the IGF1 locus or another linked gene. Since the PN and MN strains differ very markedly on their feed intake, the chicken leptin gene was included in the sequence analysis. Unfortunately, attempts to amplify several regions of this gene were unsuccessful. Even when primers complementary to highly conserved regions were used, the PCR consistently failed. Other authors have reported similar problems when trying to amplify avian leptin sequences.

Està subjecte a una llicència de Reconeixement-NoComercial-SenseObraDerivada 4.0 de Creative Commons The effect of Bioflavex ® and its pure flavonoid components on in vitro fermentation parameters and methane production in rumen fluid from steers given high concentrate diets

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-The effect of caponisation on carcass composition by parts and tissues was examined. Twenty-eight castrated and twenty male Penedesenca Negra chicks reared under free-range conditions were slaughtered at 28 weeks of age. The birds were castrated at 4 or 8 weeks. The left sides of the carcasses were quartered (wing, breast, thigh and drumstick), and the parts dissected into the tissue components (skin, subcutaneous fat, intermuscular fat, muscle, bone and tendons). Capons showed more abdominal, intermuscular and subcutaneous fat than the cocks, both at the same slaughter age and at the same weight. The breast and thigh were heavier in the capons than in the cocks. However, the whole muscle mass in the breast was increased by caponisation. This favourable effect was achieved at the expense of decreasing the carcass yield. The age of castration up to 8 weeks did not affect the carcass composition of the parts and tissues. chicken / capon / carcass / tissue composition Résumé -Comparaison du rendement à la découpe et de la composition tissulaire des carcasses de coqs et de chapons. Vingt huit chapons et vingt coqs de la race Penedesenca Negra ont été élevés sur parcours et abattus à l'âge de 28 semaines. Le chaponnage des poulets a été réalisé à deux âges différents : 4 ou 8 semaines. Après l'abattage, les morceaux (aile, pilon, cuisse et filet) correspondant à la moitié gauche de la carcasse ont été prélevés et disséqués en séparant la peau, le tissu adipeux sous-cutané, le tissu adipeux intermusculaire, les muscles, les os et les tendons. Par comparaison avec les coqs abattus au même âge ou de même poids, les chapons présentent une quantité de gras abdominal sous-cutané et intermusculaire plus élevée. Le poids de leur filet est également supérieur. En revanche, leur rendement en carcasse est inférieur. L'âge au chaponnage n'a pas d'effet sur le rendement à la découpe, ni sur la composition tissulaire de la carcasse.coq / chapon / carcasse / composition tissulaire 421

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Evidence is accumulating that intronic polymorphic cytosine-adenosine (CA) repeats may play a role in gene expression. In this work, we investigated whether a polymorphic CA short tandem repeat (STR) located at the first intron of the pig insulin-like growth factor I (IGF-I) gene influences plasma IGF-I concentration in pigs as well as phenotypic variation in growth and fatness traits. We measured plasma IGF-I levels at one to four time points from 35 to 215 days of age in 340 performance-tested Landrace and Duroc pigs previously genotyped for the IGF-I STR. Data were analyzed within breed with a linear mixed model with the number of CA repeats as a covariate. At least five alleles were segregating in each breed, differing in one to seven repeats. The results showed that in each breed, circulating IGF-I at 160 days of age increased with the length of the shortest allele, accounting for an average trend of 4.38 +/- 1.28 ng/ml of IGF-I per additional repeat (P = 0.001). Longer repeats were associated with early growth in Landrace boars (1.92 +/- 0.92 kg per CA at 160 days; P = 0.038) and with back fat thickness (-0.57 +/- 0.20 mm per CA; P = 0.005) and lean content (7.52 +/- 3.00 g/kg per CA at 105 kg; P = 0.013) adjusted for carcass weight in Duroc barrows, as expected from the effect of circulating IGF-I on these traits. The consistency of the results across populations supports the hypothesis that the length of the CA repeats at intron 1 of the IGF-I gene is associated with circulating IGF-I levels, and that this effect is not neutral with respect to growth and fatness.