Etude génétique de la qualité de la viande de poulet en relation avec le stress avant abattage

TOURS-BU Sciences Pharmacie (372612104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Specific color sensitivities of prey and predator explain camouflage in different visual systems

In situations of aggressive mimicry, predators adapt their color to that of the substrate on which they sit for hunting, a behavior that is presumed to hide them from prey as well as from their own predators. Females of few crab-spider species encounter such situations when lying on flowers to ambush pollinators. To evaluate the efficiency of spider camouflage on flowers, we measured by spectroradiometry adult female Thomisus onustus and marguerite daisies, Leucanthemum vulgare. We compared chromatic contrast (color used for short-range detection) of each pair of spider and flower to detection thresholds computed in the visual systems of both Hymenopteran prey and passerine bird predator. We also computed achromatic contrast (brightness) used for long-range detection. In both visual systems, each individual spider was efficiently matching the precise color of the flower center on which it was hunting. Being significantly darker than flowers, crab-spiders could in theory be detected at long range by either predator or prey using achromatic contrast. However, long-range detection is unlikely, owing to small spider size. Spiders also generated significant chromatic and achromatic contrasts to both Hymenoptera and bird when moving on flower periphery. Our study is the first to identify which photoreceptors of both prey and predator are involved in camouflage. The analysis suggests more research on bird predation and vision to determine to which extent bird predators effectively constrain spider crypsis. Copyright 2005.bird; camouflage; crab-spider; Hymenoptera; spectrometry

Chicken meat quality: genetic variability and relationship with growth and muscle characteristics

Abstract Background The qualitative properties of the meat are of major importance for poultry breeding, since meat is now widely consumed as cuts or as processed products. The aim of this study was to evaluate the genetic parameters of several breast meat quality traits and their genetic relationships with muscle characteristics in a heavy commercial line of broilers. Results Significant levels of heritability (averaging 0.3) were obtained for breast meat quality traits such as pH at 15 min post-slaughter, ultimate pH (pHu), color assessed by lightness L*, redness a* and yellowness b*, drip loss, thawing-cooking loss and shear-force. The rate of decrease in pH early post-mortem and the final pH of the meat were shown to be key factors of chicken meat quality. In particular, a decrease in the final pH led to paler, more exudative and tougher breast meat. The level of glycogen stored in breast muscle estimated by the Glycolytic Potential (GP) at slaughter time was shown to be highly heritable (h2 0.43). There was a very strong negative genetic correlation (rg) with ultimate meat pH (rg -0.97), suggesting a common genetic control for GP and pHu. While breast muscle weight was genetically positively correlated with fiber size (rg 0.76), it was negatively correlated with the level of glycogen stored in the muscle (rg -0.58), and as a consequence it was positively correlated with the final pH of the meat (rg 0.84). Conclusion This genetic study confirmed that selection should be useful to improve meat characteristics of meat-type chickens without impairing profitability because no genetic conflict was detected between meat quality and meat quantity. Moreover, the results suggested relevant selection criteria such as ultimate pH, which is strongly related to color, water-holding capacity and texture of the meat in this heavy chicken line.</p

Technological quality of broiler breast meat in relation to muscle hypertrophy

International audienc

Technological quality of broiler breast meat in relation to muscle hypertrophy

International audienc

Consequence of muscle hypertrophy on characteristics of Pectoralis major muscle and breast meat quality of broiler chickens

International audienceThe structural and metabolic characteristics of the pectoralis major (P. major) muscle (i.e., breast muscle) and the quality of the resulting meat were studied in relation to breast muscle fiber development in broiler chickens. Six hundred birds originating from a commercial, grand parental, male heavy line (Hubbard-Europe, Chateaubourg, France) were kept under conventional breeding methods until their usual marketing age of 6 wk. For all birds, the plasma creatine kinase activity and the P. major muscle fiber cross-sectional area (CSA), glycolytic potential, lactate content, pH at 15 min postmortem, as well as the ultimate pH, CIELAB color parameters [lightness ( L*), redness (a*), and yellowness (b*)], and drip loss of breast meat, were measured. Increased breast weight and yield were associated with increased fiber CSA, reduced muscle glycolytic potential, and reduced lactate content at 15 min postmortem. Therefore, P. major muscle exhibiting larger fiber CSA exhibited greater pH at 15 min postmortem and ultimate pH, produced breast meat with lower L* and reduced drip loss, and was potentially better adapted to further processing than muscle exhibiting small fiber CSA

Hypertrophie des fibres musculaires. Conséquence pour la qualité technologique du filet de poulet

National audienceThe purpose of this study was to relate the breast muscle development, including muscle fibre size, to the postmortem metabolism and the further breast meat quality. Phenotypic and genetic relationships between fibre andmeat traits were estimated for a total of 600 commercial broilers. For all birds, we measured muscle fibre crosssectional area (CSA), glycolytic potential, lactate content, post-mortem pH fall and classical meat quality traits(colour, drip and thawing-cooking loss, Warner-Bratzler shear force) in the Pectoralis major (PM) muscle. Wealso determined the occurrence of giant fibres in relation to muscle fibre size and post-mortem metabolism. Asthe fibre CSA increased, both the glycogen reserve at death (glycolytic potential) and the post-mortem glycolyticactivity of muscle decreased. As a consequence, PM muscles with the largest fibres exhibited the highest pH15and pHu. Therefore, PM muscles with the largest fibres exhibited the lowest L*, drip and thawing-cooking lossesand were more tender after cooking. Whatever the muscle fibre diameter, the occurrence of giant fibres greatlyincreased when muscle pH15 was below 6.30. However, in muscles with pH15 above 6.30, the proportion ofmuscles in which giant fibres occurred was greater in muscles exhibiting large fibres than in muscles exhibitingsmall fibres. This suggests that the occurrence of giant fibres would be more sensitive to rapid pH fall rate inmuscles with large fibres than in muscle with small fibres. In conclusion, this study did not evidence anyantagonism between growth rate or muscle development and breast meat quality and suggested that meat ofcurrent broiler genotypes, selected for growth and breast yield, are well adapted to further processing.Cette Ètude avait pour objectif díÈtudier líimpact de líhypertrophie musculaire sur le mÈtabolisme post-mortemet la qualitÈ du filet de poulet. Sur un effectif pedigree de 600 poulets commerciaux lourds, nous avonsdÈterminÈ sur le muscle Pectoralis major (PM) líaire de section transversale des fibres, le potentiel glycolytique,le lactate et le pH ‡ 15 min (pH15), le pH ultime (pHu), les paramËtres de couleur L*, a*, b*, les pertes parexsudation et aprËs dÈcongÈlation-cuisson et la force maximale de cisaillement de la viande cuite. Nous avonsaussi ÈvaluÈ la proportion de fibres gÈantes hypercontractÈes (FGH) en relation ‡ la fois avec la taille des fibreset la vitesse de chute de pH post-mortem. Líhypertrophie des fibres entraÓne une rÈduction des rÈserves englycogËne au moment de la mort et un ralentissement de líactivitÈ glycolytique post-mortem. Il en rÈsulte desviandes avec des pH15 et pHu plus ÈlevÈs, un meilleur pouvoir de rÈtention en eau et une tendretÈ supÈrieureaprËs cuisson. Quel que soit le diamËtre des fibres musculaires, líapparition de FGH augmente significativementlorsque le pH15 est infÈrieur ‡ 6,30. Toutefois, lorsque le pH15 est supÈrieur ‡ 6,30, la proportion de musclescontenant des FGH est plus ÈlevÈe dans les muscles prÈsentant de grosses fibres que dans les musclesprÈsentant des petites fibres. Ceci suggËre que líapparition de FGH serait plus sensible aux vitesses de chute depH rapides dans les muscles contenant les fibres les plus grosses. En conclusion, cette Ètude ne met pas enÈvidence díantagonisme entre croissance ou dÈveloppement musculaire et qualitÈ des viandes, et suggËre que lesgÈnotypes sÈlectionnÈs pour ces critËres sont plutÙt bien adaptÈs aux procÈdÈs de transformation actuels

Hypertrophie musculaire: conséquence pour la qualité technologique du filet de poulet

National audienc