30 research outputs found
Detection of genes influencing economic traits in three French dairy cattle breeds
A project of QTL detection was carried out in the French Holstein, Normande, and Montbéliarde dairy cattle breeds. This granddaughter design included 1 548 artificial insemination bulls distributed in 14 sire families and evaluated after a progeny-test for 24 traits (production, milk composition, persistency, type, fertility, mastitis resistance, and milking ease). These bulls were also genotyped for 169 genetic markers, mostly microsatellites. The QTL were analysed by within-sire linear regression of daughter yield deviations or deregressed proofs on the probability that the son receives one or the other paternal QTL allele, given the marker information. QTL were detected for all traits, including those with a low heritability. One hundred and twenty QTL with a chromosome-wise significance lower than 3% were tabulated. This threshold corresponded to a 15% false discovery rate. Amongst them, 32 were genome-wise significant. Estimates of their contribution to genetic variance ranged from 6 to 40%. Most substitution effects ranged from 0.6 to 1.0 genetic standard deviation. For a given QTL, only 1 to 5 families out of 14 were informative. The confidence intervals of the QTL locations were large and always greater than 20 cM. This experiment confirmed several already published QTL but most of them were original, particularly for non-production traits
Detection of quantitative trait loci for growth and fatness in pigs
A quantitative trait locus (QTL) analysis of growth and fatness data from a three-generation experimental cross between Meishan (MS) and Large White (LW) pig breeds is presented. Six boars and 23 F1 sows, the progeny of six LW boars and six MS sows, produced 530 F2 males and 573 F2 females. Nine growth traits, i.e. body weight at birth and at 3, 10, 13, 17 and 22 weeks of age, average daily gain from birth to 3 weeks, from 3 to 10 weeks and from 10 to 22 weeks of age, as well as backfat thickness at 13, 17 and 22 weeks of age and at 40 and 60 kg live weight were analysed. Animals were typed for a total of 137 markers covering the entire porcine genome. Analyses were performed using two interval mapping methods: a line-cross (LC) regression method where founder lines were assumed to be fixed for different QTL alleles and a half-/full-sib (HFS) maximum likelihood method where allele substitution effects were estimated within each half-/full-sib family. Both methods revealed highly significant gene effects for growth on chromosomes 1, 4 and 7 and for backfat thickness on chromosomes 1, 4, 5, 7 and X, and significant gene effects on chromosome 6 for growth and backfat thickness. Suggestive QTLs were also revealed by both methods on chromosomes 2 and 3 for growth and 2 for backfat thickness. Significant gene effects were detected for growth on chromosomes 11, 13, 14, 16 and 18 and for backfat thickness on chromosome 8, 10, 13 and 14. LW alleles were associated with high growth rate and low backfat thickness, except for those of chromosome 7 and to a lesser extent early-growth alleles on chromosomes 1 and 2 and backfat thickness alleles on chromosome 6
Detection of QTL controlling feed efficiency and excretion in chickens fed a wheat-based diet
Apports actuels et futurs des marqueurs gĂ©nĂ©tiques dans lâamĂ©lioration des populations animales. Les contrĂŽles de filiation dans les populations
Le contrĂŽle de filiation est utilisĂ© par les organismes en charge de lâamĂ©lioration gĂ©nĂ©tique des espĂšces dâĂ©levage. Il permet de contrĂŽler lâexactitude des gĂ©nĂ©alogies enregistrĂ©es dans les fichiers des chaĂźnes nationales dâidentification. Il est rĂ©alisĂ© en comparant les hĂ©motypes des trois membres (pĂšre, mĂšre, produit) des familles contrĂŽlĂ©es. Les analyses comportent un grand nombre de tests immunologiques et biochimiques confĂ©rant au contrĂŽle de filiation une grande efficacitĂ© dans la dĂ©tection des familles erronĂ©es
Utilisation de marqueurs génétiques en sélection : les activités de Labogena
National audienceLe diagnostic gĂ©nĂ©tique appliquĂ© Ă la sĂ©lection animale nâest pas rĂ©cent, mais des progrĂšs fantastiques ont Ă©tĂ© rĂ©alisĂ©s ces derniĂšres annĂ©es grĂące Ă lâĂ©mergence des techniques de biologie molĂ©culaire. LâĂ©volution du nombre dâanalyses rĂ©alisĂ©es par LABOGENA, 45 000 en 1988 pour plus de 100 000 en 1998, est bien la preuve de cet essor. Si deux tiers des activitĂ©s demeurent traditionnelles, 30 % sont rĂ©alisĂ©es grĂące aux marqueurs de lâADN et la tendance va encore sâaccentuer. La biologie molĂ©culaire permet de rĂ©aliser des progrĂšs et dâaugmenter les possibilitĂ©s de diagnostic : les supports biologiques utilisables sont nombreux (sang, poil, peau, viande, embryon, sperme âŠ) ; lâĂ©mergence de nouveaux marqueurs polymorphes comme les marqueurs microsatellites de lâADN permet lâidentification et le contrĂŽle de filiations pour de nouvelles espĂšces (Porc, Chien, Turbot âŠ) ; les diagnostics peuvent ĂȘtre rĂ©alisĂ©s trĂšs prĂ©cocement par lâanalyse directe des variations des gĂšnes impliquĂ©s (exemple de la qualitĂ© fromagĂšre du lait dĂ©terminĂ©e sur les futurs reproducteurs mĂąles) ; les pathologies dâorigine gĂ©nĂ©tique peuvent ĂȘtre recherchĂ©es par les mutations causales (hyperthermie maligne, tremblante âŠ). Ces informations sur les gĂ©notypes aident les sĂ©lectionneurs Ă dĂ©finir leurs stratĂ©gies et permettent dâassurer une bonne gestion des reproducteurs et des populations animales
Genetic determinism of fearfulness, general activity and feeding behavior in chickens and its relationship with digestive efficiency
The genetic relationships between behavior and digestive efficiency were studied in 860 chickens from a cross between two lines divergently selected on digestive efficiency. At 2Â weeks of age each chick was video-recorded in the home pen to characterize general activity and feeding behavior. Tonic immobility and open-field tests were also carried out individually to evaluate emotional reactivity (i.e. the propensity to express fear responses). Digestive efficiency was measured at 3Â weeks. Genetic parameters of behavior traits were estimated. Birds were genotyped on 3379 SNP markers to detect QTLs. Heritabilities of behavioral traits were low, apart from tonic immobility (0.17â0.18) and maximum meal length (0.14). The genetic correlations indicated that the most efficient birds fed more frequently and were less fearful. We detected 14 QTL (9 for feeding behavior, 3 for tonic immobility, 2 for frequency of lying). Nine of them co-localized with QTL for efficiency, anatomy of the digestive tract, feed intake or microbiota composition. Four genes involved in fear reactions were identified in the QTL for tonic immobility on GGA1
Genetic determinism of bone and mineral metabolism in meat-type chickens: A QTL mapping study
Skeletal integrity in meat-type chickens is affected by many factors including rapid growth rate, nutrition and genetics. To investigate the genetic basis of bone and mineral metabolism, a QTL detection study was conducted in an intercross between two lines of meat-type chickens divergently selected for their high (D+) or low (Dâ) digestive efficiency. Tibia size (length, diameter, volume) and ash content were determined at 3Â weeks of age as well as phosphorus (P) retention and plasma concentration. Heritability of these traits and their genetic correlations with digestive efficiency were estimated. A QTL mapping study was performed using 3379 SNP markers.Tibia size, weight, ash content and breaking strength were highly heritable (0.42 to 0.61). Relative tibia diameter and volume as well as P retention were strongly and positively genetically correlated with digestive efficiency (0.57 to 0.80).A total of 35 QTL were identified (9 for tibia weight, 13 for tibia size, 5 for bone strength, 5 for bone mineralization, 2 for plasma P concentration and 1 for P retention). Six QTL were genome-wide significant, and 3 QTL for tibia relative volume, weight and ash weight on chromosome 6 were fixed, the positive allele coming from the D-line. For two QTL for ash content on chromosome 18 and relative tibia length on chromosome 26, the confidence intervals were small enough to identify potential candidate genes.These findings support the evidence of multiple genetic loci controlling bone and mineral metabolism. The identification of candidate genes may provide new perspectives in the understanding of bone regulation, even beyond avian species. Keywords: Chicken, QTL, Genetic parameters, Phosphorus, Environment, Bon