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Towards the quantitative characterisation of piglets’ robustness to weaning: A modelling approach

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M Revilla et al., Animal, 2019, volume 16, mai, 11 pages

Weaning is a critical transition phase in swine production in which piglets must cope with different stressors that may affect their health. During this period, the prophylactic use of antibiotics is still frequent to limit piglet morbidity, which raises both economic and public health concerns such as the appearance of antimicrobial-resistant microbes. With the interest of developing tools for assisting health and management decisions around weaning, it is key to provide robustness indexes that inform on the animals’ capacity to endure the challenges associated with weaning. This work aimed at developing a modelling approach for facilitating the quantification of piglet resilience to weaning. A total of 325 Large White pigs weaned at 28 days of age were monitored and further housed and fed conventionally during the post-weaning period without antibiotic administration. Body weight and diarrhoea scores were recorded before and after weaning, and blood was sampled at weaning and 1 week later for collecting haematological data. A dynamic model was constructed based on the Gompertz–Makeham law to describe live weight trajectories during the first 75 days after weaning, following the rationale that the animal response is partitioned in two time windows (a perturbation and a recovery window). Model calibration was performed for each animal. Our results show that the transition time between the two time windows, as well as the weight trajectories are characteristic for each individual. The model captured the weight dynamics of animals at different degrees of perturbation, with an average coefficient of determination of 0.99, and a concordance correlation coefficient of 0.99. The utility of the model is that it provides biologically meaningful parameters that inform on the amplitude and length of perturbation, and the rate of animal recovery. Our rationale is that the dynamics of weight inform on the capability of the animal to cope with the weaning disturbance. Indeed, there were significant correlations between model parameters and individual diarrhoea scores and haematological traits. Overall, the parameters of our model can be useful for constructing weaning robustness indexes by using exclusively the growth curves. We foresee that this modelling approach will provide a step forward in the quantitative characterisation of robustness.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/18FBD3614BA779E09D061744323CF5DD/S1751731119000843a.pdf/towards_the_quantitative_characterisation_of_piglets_robustness_to_weaning_a_modelling_approach.pdf

2019

Evaluations génétiques et génomiques des populations porcines

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Sandrine Schwob, Alban Bouquet et Pauline Brenaut, Bilan 2018, éditions IFIP, avril 2019, p. 84

Le travail de sélection a pour but d’améliorer le niveau moyen des performances des populations porcines sur des caractères d’intérêt économique pour l’ensemble de la filière porcine française. Ce travail d’amélioration génétique consiste à repérer les meilleurs individus d’une génération pour les garder comme reproducteurs. Pour cela, des modèles statistiques prédisent la valeur génétique (VG) des candidats à la sélection à partir de leurs performances propres et de celles de leurs apparentés et contemporains. L’information du génome des animaux est également prise en compte dans les lignées femelles Large White (LW) et Landrace français (LF). Chaque semaine, les meilleurs candidats LW et LF sont génotypés sur puces ADN basse densité. Puis les génotypages haute densité sont reconstitués par imputation, permettant ainsi d’optimiser les coûts. Pour consolider les populations de référence, les reproducteurs les plus utilisés en sélection sont de nouve

PDF icon Sandrine Schwob, Alban Bouquet et Pauline Brenaut, Bilan 2018, éditions IFIP, avril 2019, p. 84
2019

Etude de la composante génétique du défaut « jambon déstructuré »

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Sandrine Schwob, bilan 2018, éditions IFIP, avril 2019, p. 57

Le défaut « jambon déstructuré » constitue un handicap majeur dans la technologie de fabrication du jambon cuit. Actuellement, il n’est détectable qu’après désossage du jambon, ce qui complique son élimination. Cette étude a pour objectif de mieux comprendre l’origine génétique du défaut afin de réduire la fréquence d’apparition par la voie génétique.

PDF icon Sandrine Schwob, bilan 2018, éditions IFIP, avril 2019, p. 57
2019

Genomic data reveals large similarities among Canadian and French maternal pig lines

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Raphaël Boré et al., Canadian Journal of Animal Science, volume 98, n° 4, décembre, p. 809-817

Combiner des populations de référence provenant de différents pays ou de différentes races peut être un moyen abordable d’agrandissement de la taille de la population de référence pour les prédictions génomiques. Par conséquent, les principaux objectifs de cette étude sont d’évaluer la diversité génomique entre et au sein des deux races porcines françaises et canadiennes (Landrace et Yorkshire) ainsi que l’apparentement des populations afin d’évaluer la faisabilité de combiner les populations de référence des deux pays en une population de référence commune pour la sélection génomique porcine. Un total de 14,756 animaux ont été génotypés sur deux puces à ADN commerciales (~ 65K SNPs). L’analyse en composantes principales discrimine clairement les deux races Landrace et Yorkshire, et dans une moindre mesure les populations de chacun des deux pays. Le déséquilibre de liaison (LD) entre les SNPs adjacents est similaire dans les populations Yorkshire. En revanche, les niveaux de LD sont légèrement différents pour les populations Landrace. La persistance de phase gamétique entre les populations Yorkshire est très élevée (0.96 à une distance de 0.05 Mb) et élevée entre les populations Landrace (0.88 à une distance de 0.05 Mb). Ces persistances de phase gamétique élevées suggèrent que les lignées maternelles canadiennes et françaises sont génétiquement proches les unes des autres. Ces résultats sont prometteurs et indiquent que la précision des valeurs génomiques estimées pourrait augmenter avec une population de référence commune entre le Canada et la France.

https://www.nrcresearchpress.com/doi/pdf/10.1139/cjas-2017-0103

Genomic data reveals large similarities among Canadian and French maternal pig lines

Combining reference populations from different countries and breeds could be an affordable way to enlarge the size of the reference populations for genomic prediction of breeding values. Therefore, the main objectives of this study were to assess the genetic diversity within and between two Canadian and French pig breeds (Landrace and Yorkshire) and the genomic relatedness among populations in order to evaluate the feasibility of an across-country reference population for pig genomic selection. A total of 14,756 pigs were genotyped on two SNP chip panels (~65K SNPs). A principal component analysis clearly discriminated Landrace and Yorkshire breeds, and also, but to a lesser extent, the Canadian and French purebred pigs of each breed. Linkage disequilibrium (LD) between adjacent SNPs was similar within Yorkshire populations. However, levels of LD were slightly different for Landrace populations. The consistency of gametic phase was very high between Yorkshire populations (0.96 at 0.05 Mb) and high for Landrace (0.88 at 0.05 Mb). Based on consistency of gametic phase, Canadian and French pig maternal lines are genetically close to each other.
These results are promising, as they indicate that the accuracy of estimated genomic breeding values may increase by combining reference populations from the two countries.

https://www.nrcresearchpress.com/doi/pdf/10.1139/cjas-2017-0103

2018

Diversity across major and candidate genes in European local pig breeds

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Maria Munoz et al., 2018, Plos One, 20 novembre, 30 pages

The aim of this work was to analyse the distribution of causal and candidate mutations associated to relevant productive traits in twenty local European pig breeds. Also, the potential of the SNP panel employed for elucidating the genetic structure and relationships among breeds was evaluated. Most relevant genes and mutations associated with pig morphological, productive, meat quality, reproductive and disease resistance traits were prioritized and analyzed in a maximum of 47 blood samples from each of the breeds (Alentejana, Apulo-Calabrese, Basque, Bísara, Majorcan Black, Black Slavonian (Crna slavonska), Casertana, Cinta Senese, Gascon, Iberian, Krškopolje (Krškopoljski), Lithuanian indigenous wattle, Lithuanian White Old Type, Mora Romagnola, Moravka, Nero Siciliano, Sarda, Schwäbisch-Hällisches Schwein (Swabian Hall pig), Swallow-Bellied Mangalitsa and Turopolje). We successfully analyzed allelic variation in 39 polymorphisms, located in 33 candidate genes. Results provide relevant information regarding genetic diversity and segregation of SNPs associated to production and quality traits. Coat color and morphological trait-genes that show low level of segregation, and fixed SNPs may be useful for traceability. On the other hand, we detected SNPs which may be useful for association studies as well as breeding programs. For instance, we observed predominance of alleles that might be unfavorable for disease resistance and boar taint in most breeds and segregation of many alleles involved in meat quality, fatness and growth traits. Overall, these findings provide a detailed catalogue of segregating candidate SNPs in 20 European local pig breeds that may be useful for traceability purposes, for association studies and for breeding schemes. Population genetic analyses based on these candidate genes are able to uncover some clues regarding the hidden genetic substructure of these populations, as the extreme genetic closeness between Iberian and Alentejana breeds and an uneven admixture of the breeds studied. The results are in agreement with available knowledge regarding breed history and management, although largest panels of neutral markers should be employed to get a deeper understanding of the population’s structure and relationships.

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0207475&type=printable

2018

Complete genome sequence of Salmonella enterica subsp. enterica Serotype Derby, associated with the pork sector in France

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Yann Sévellec et al., Microbiology Resource Announcements, volume 7, n° 12, septembre, 4 pages

In the European Union, Salmonella enterica subsp. enterica serovar Derby is the most abundant serotype isolated from pork. Recent studies have shown that this serotype is polyphyletic. However, one main genomic lineage, characterized by sequence type 40 (ST40), the presence of the Salmonella pathogenicity island 23, and showing resistance to streptomycin, sulphonamides, and tetracycline (STR-SSS-TET), is pork associated. Here, we describe the complete genome sequence of a strain from this lineage isolated in France.

https://mra.asm.org/content/ga/7/12/e01027-18.full-text.pdf

2018

Impact of weaning age on gut microbiota composition in piglets

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F.R. Massacci et al., 69th Annual meeting of the european federation of animal science (EAAP), Dubrovnik, Croatie, 27-31 août 2018

Weaning is a crucial period of pigs, accompanied by nutritional, environmental and social stresses. Studies comparing different ages at weaning have shown that increasing weaning age improves wean-to-finish growth performances and reduces mortality. However, the impact of weaning age on the early-life establishment of the gut microbiota remains under-investigated in pigs. Our objective was to compare the gut microbiota composition of piglets weaned at different ages. 48 piglets were divided in 4 groups of 12 animals weaned at either 14, 21, 28 or 42 days-of-age.
Faecal samples were collected at 3 different time points: day of weaning, 7 days after weaning and at 60 days of age. Faecal DNA bacterial composition was assessed by sequencing the V3-V4 regions of the 16S rRNA gene.
Bioinformatic and biostatistical analysis showed that each weaned group had significant differences between the sample points through weaning transition, confirming that the gut microbiota changes before and after weaning. In addition, microbiota diversity increased according to weaning age, with piglets weaned at 42 days-of-age having a highest alpha diversity and richness. Interestingly, piglets weaned at 42-days maintained a more stable diversity until day 60. We show that late weaning leads to a higher diversity of potentially beneficial microbes prior to the crucial challenge of weaning and might thus provide a competitive advantage to piglets.

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2018

An online phenotype database: first step towards breeding programs in local pig breeds

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Marie-José Mercat et al., 69th Annual Meeting of the European Federation of Animal Science (EAAP), Dubrovnik, Croatie, le 27-31 août 2018, visuels d'intervention

In order to further allow implementation of breeding programs in local pig breeds, with selection objectives defined for each local breed, we aimed at developing a standardised recording of carcass and meat quality traits. These data have to be connected with herdbooks to estimate genetic parameters of the traits (heritabilities and genetic correlations) which are necessary to define breeding objectives. Today the situation is very different from one local breed to another. No or very few phenotypes are recorded in some of them, while breeding programs already exist for a few breeds. To promote phenotyping, a dedicated database and a website were developed in the frame of the TREASURE project. First, the required variables have been collected for six local breeds: Basque (FR), Bísaro (PT), Crna slavonska (HR), Gascon (FR), Krškopoljski (SI) and Schwäbisch-Hällisches (DE). In total 74 variables have been identified dealing with animal herdbook information (10), rearing and growth (22), carcass (22) and meat quality (20) attributes. The database is compatible with the various identifiers used in the different countries: animal IDs, breed, farm… codifications. Major attention has been paid to the description of measurement methods of traits. Thus, each carcass and meat quality phenotype is associated to a method description representing 35 additional variables. The website can be easily translated into several languages. The website and database are currently on test until the end of the TREASURE project. All the breeds studied in TREASURE are free to use these tools. The database can be duplicated so that each partner can host its own data. Funded by European Union H2020 RIA program (grant agreement no. 634476).

PDF icon Marie-José Mercat et al., 69th EAAP, Dubrovnik, Croatie, le 27-31 août 2018
2018

Gut microbiota analyses for sustainable European local porcine breeds: A TREASURE pilot study

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J. Estellé et al., 69th Annual meeting of the european federation of animal science (EAAP), Dubrovnik, Croatie, 27-31 août 2018

The study of gut microbiota and its effects on hosts has emerged as an essential component of host homeostasis and global efficiency. Besides host’s influence on gut microbiota, major quantitative and qualitative changes may occur in the composition of the intestinal microbiota due to the influence of diet and other environmental factors.
In accordance with the TREASURE project global aim of enhancing sustainability of production systems for local pig breeds, the objective of our task was to conduct a pilot characterisation of intestinal microbiota in order to test its usefulness to characterize several local European pig populations and their production systems. This approach has been applied to populations belonging to the following European traditional breeds: Gascon (France), Iberian (Spain), Krskopolje (Slovenia), Mangalitsa (Serbia), Moravka (Serbia) and Turopolje (Croatia). For each breed, faecal samples have been collected along different experiments performed in the TREASURE project targeting the comprehension of a particular traditional production system (e.g. open-air farming), management practice, or the comparison of breeds. In all experiments, the metagenomics technique employed is the re-sequencing of the bacterial 16S in an Illumina MiSeq system. Overall, the results have shown that the gut microbiota analysis is a promising approach for the characterisation of these local breeds, by allowing a deeper understanding of their production systems and potentially allowing the development of new certification approaches. Preliminary results will be summarized in this communication. Funded by European Union’s H2020 RIA program (Grant agreement no. 634476).

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2018

On the influence of host genetics on gut microbiota composition in pigs

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J. Estellé et al., 69th Annual meeting of the european federation of animal science (EAAP), Dubrovnik, Croatie, 27-31 août 2018

Gut microbial population acts in complement with its host through nutrient digestion and health of the gastrointestinal tract. Changes in microbiota composition may then lead to changes in nutrient digestibility. The present study aimed at determining the effects of dietary fibre content on gut microbiota composition and apparent faecal nutrient digestibility in pigs. Furthermore, the relationships between microbiota and digestibility coefficients were investigated. Growing-finishing pigs (from 35 to 74 kg mean body weight) were fed alternatively a low-fibre (LF) and a high-fibre (HF) diet during 4 successive 3-week periods. Data collection for digestibility measurements was achieved during the last week of each period and faecal microbiota was collected at the end of each period for 16S rRNA gene sequencing. The two diets fed by the pigs could be discriminated using 31 predicting OTUs in a sparse partial least square discriminant analysis (mean classification error-rate 3.9%). Furthermore, microbiota was resilient to diet effect. Pearson correlations between microbiota composition and apparent digestibility coefficients of energy, protein, cellulose and hemicellulose emphasized the fact that in LF group, Clostridiaceae and Turicibacter were negatively correlated with protein and energy digestibility coefficients whereas Lactobacillus was positively correlated. In addition, Lachnospiraceae and Prevotella were negatively correlated with cell wall components digestibility. In HF diet, no significant correlation between microbiota and digestibility was found. The present study demonstrates that 3 weeks of adaptation to a new diet seem to be sufficient to observe resilience in growing pigs gut microbiota. In addition, faecal microbiota can be used to classify pigs according to their diet. Because some bacterial family and genera are favourable to digestibility, this study suggests that manipulations of bacterial populations can improve digestibility and feed efficiency. This study is part of the Feed-a-Gene Project, funded from the European Union’s H2020 Programme under grant agreement no. 633531.

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2018

Integrating blood transcriptome and immunity traits to identify markers of immune capacity in pigs

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T. Maroilley et al., 69th Annual meeting of the european federation of animal science (EAAP), Dubrovnik, Croatie, 27-31 août 2018

Understanding individual variability of immune capacity in livestock has become a priority to improve sustainability, with the aim to increase disease resistance and resilience in breeding programs. In this study, 550 60-day-old French Large White pigs vaccinated against Mycoplasma hyopneumoniae (M hyo) were monitored for 55 immunity traits (ITs) measured from blood samples (SUS_FLORA ANR funded project). The ITs included two types of parameters. First, parameters directly measured from blood: complete blood counts, counts of various cell subsets by flow cytometry, serum dosage of anti-M hyo IgG and haptoblobin. Second, parameters measured after in vitro stimulation of total blood: phagocytosis, production of cytokines (IL-1&”6;, IL-8, IL-10, IL-17, TNF&”5;, IFN&”7;) after stimulation by LPS or mitogenic agents. All animals were genotyped with 60K Illumina SNP chips. A subset of 243 piglets was chosen for blood transcriptome analysis using Agilent microarrays. We explored covariations between blood expression profiles and IT levels, and could draw lists of the most correlated genes with each IT. Each list represented candidate blood biomarkers potentially predictive of IT variations. As an example, we found 134 genes associated with phagocytosis capacity and we identified a subset of genes that could significantly predict levels of eight ITs related to phagocytosis by a sPLS approach. This gene subset included CXCR1, CCR1 and TLR2. Few candidate biomarkers were previously shown to be genetically controlled for their transcription in blood by eGWAS. Thus, our results provide new data to decipher the genetic architecture of IT variations. A next step will be to understand how IT variations could reflect individual robustness while facing pathogens, and how blood biomarkers could be used as predictors of immune capacity.

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2018

Evaluations génétiques et génomiques des populations porcines

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Sandrine Schwob, Alban Bouquet et Pauline Brehaut, bilan 2017, éditions IFIP, mai 2018, p. 53

Le travail de sélection a pour but d’améliorer le niveau moyen des performances des populations porcines sur des caractères d’intérêt économique pour l’ensemble de la filière porcine française. Ce travail d’amélioration génétique consiste à repérer les meilleurs individus d’une génération pour les garder comme reproducteurs. Pour cela, des modèles statistiques prédisent la valeur génétique (VG) des candidats à la sélection à partir de leurs performances propres et de celles de leurs apparentés et contemporains. Chaque semaine, cinq populations porcines (4 collectives : Large White lignée femelle, Landrace français, Piétrain et Large White lignée mâle, et 1 autonome : Duroc Axiom) sont évaluées et les VG sont transmises aux sélectionneurs, organismes de sélection porcine (OSP), groupements d’éleveurs et centres d’insémination animale (CIA).

PDF icon Sandrine Schwob, Alban Bouquet et Pauline Brehaut, bilan 2017, éditions IFIP, mai 2018, p. 53, fiche n° 24
2018

Immunome differences between porcine ileal and jejunal Peyer’s patches revealed by global transcriptome sequencing of gut-associated lymphoid tissues

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T. Maroilley et al., Scientific Reports, 2018, volume 8, n° 1, 13 juin, 12 pages

The epithelium of the intestinal mucosa and the gut-associated lymphoid tissues (GALT) constitute an essential physical and immunological barrier against pathogens. In order to study the specificities of the GALT transcriptome in pigs, we compared the transcriptome profiles of jejunal and ileal Peyer’s patches (PPs), mesenteric lymph nodes (MLNs) and peripheral blood (PB) of four male piglets by RNA-Seq. We identified 1,103 differentially expressed (DE) genes between ileal PPs (IPPs) and jejunal PPs (JPPs), and six times more DE genes between PPs and MLNs. The master regulator genes FOXP3GATA3STAT4TBX21 and RORC were less expressed in IPPs compared to JPPs, whereas the transcription factor BCL6 was found more expressed in IPPs. In comparison between IPPs and JPPs, our analyses revealed predominant differential expression related to the differentiation of T cells into Th1, Th2, Th17 and iTreg in JPPs. Our results were consistent with previous reports regarding a higher T/B cells ratio in JPPs compared to IPPs. We found antisense transcription for respectively 24%, 22% and 14% of the transcripts detected in MLNs, PPs and PB, and significant positive correlations between PB and GALT transcriptomes. Allele-specific expression analyses revealed both shared and tissue-specific cis-genetic control of gene expression.

https://www.nature.com/articles/s41598-018-27019-7.pdf

2018

Using 1K SNP panel for genomic selection in 3 French pig breeds: Accuracy of Imputation and estimation of genomic breeding values using 1K SNP panel, designed for several breeds in French pig populations

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Céline Carillier-Jacquin (Université de Toulouse, INRA, INPTet ENVT)  et al., World Congress on Genetics Applied to Livestock Production, Auckland, Nouvelle-Zélande, 11–16 février 2018, p. 294-298

The current cost of medium density SNP chips is a limit to the development of genomic selection in pig populations (Badke et al., 2014; Wellmann et al., 2013). To reduce the cost of genotyping, a low density (LD) SNP chip was designed in 2016 and has been used in routine.
This LD panel of around 1100 SNP was optimized for imputation accuracy in the French Landrace (Land) pig population using equally spaced SNP with minor allele frequency (MAF) larger than 0.2. In the present study, we proposed to adapt the panel to two other major French pig breeds i.e. Large White (LW) and Pietrain (PI) lines. Imputation accuracy as well as the impact on genomic estimated breeding value (GEBV) were estimated in the three breeds using this new SNP chip design.

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2018

Building and evaluation of SNPs panels for parentage tests issue in swine

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G Even et al., World Congress on Genetics Applied to Livestock Production, Auckland, Nouvelle Zélande, 11-16 février 2018, posters

Three SNPs panels have been defined for parentage testing in swine containing 100, 200 and 329 SNPs, respectively. Markers have been chosen from the Illumina 60K version 2 chip based on Minor Allele Frequencies (MAF) estimated on twelve breeds used in France. A validation test has been performed confronting products genotypes with those of their right parents or those of animals related or unrelated to their right parents.

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2018

Deciphering the genetic regulation of peripheral blood transcriptome in pigs through expression genome-wide association study and allele-specific expression analysis

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T. Maroilley et al., BMC Genomics, 2017, 13 décembre, volume 18, n° 1, 13 décembre,19 pages

Abstract

BACKGROUND:

Efforts to improve sustainability in livestock production systems have focused on two objectives: investigating the genetic control of immune function as it pertains to robustness and disease resistance, and finding predictive markers for use in breeding programs. In this context, the peripheral blood transcriptome represents an important source of biological information about an individual's health and immunological status, and has been proposed for use as an intermediate phenotype to measure immune capacity. The objective of this work was to study the genetic architecture of variation in gene expression in the blood of healthy young pigs using two approaches: an expression genome-wide association study (eGWAS) and allele-specific expression (ASE) analysis.

RESULTS:

The blood transcriptomes of 60-day-old Large White pigs were analyzed by expression microarrays for eGWAS (242 animals) and by RNA-Seq for ASE analysis (38 animals). Using eGWAS, the expression levels of 1901 genes were found to be associated with expression quantitative trait loci (eQTLs). We recovered 2839 local and 1752 distant associations (Single Nucleotide Polymorphism or SNP located less or more than 1 Mb from expression probe, respectively). ASE analyses confirmed the extensive cis-regulation of gene transcription in blood, and revealed allelic imbalance in 2286 SNPs, which affected 763 genes. eQTLs and ASE-genes were widely distributed on all chromosomes. By analyzing mutually overlapping eGWAS results, we were able to describe putative regulatory networks, which were further refined using ASE data. At the functional level, genes with genetically controlled expression that were detected by eGWAS and/or ASE analyses were significantly enriched in biological processes related to RNA processing and immune function. Indeed, numerous distant and local regulatory relationships were detected within the major histocompatibility complex region on chromosome 7, revealing ASE for most class I and II genes.

CONCLUSIONS:

This study represents, to the best of our knowledge, the first genome-wide map of the genetic control of gene expression in porcine peripheral blood. These results represent an interesting resource for the identification of genetic markers and blood biomarkers associated with variations in immunity traits in pigs, as well as any other complex traits for which blood is an appropriate surrogate tissue.

2017

Genomics to estimate additive and dominance genetic variances in purebred and crossbred pig traits

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L. Tusell et al. 68th Annual Meeting of the European Federation of Animal Science, Tallinn, Estonie, 28 août-01 septembre 2017, poster

ABSTRACT

This study aims at assessing the contribution of the additive and dominance genomic variances to the phenotype expression of several purebred Piétrain and crossbred (Piétrain x Large White) pig performances. A total of 636 purebred and 720 crossbred male piglets were phenotyped for 22 traits that can be classified into growth rate and feed efficiency, carcass composition, meat quality, behavior, boar taint and puberty groups of traits. Additive and dominance variances estimated in univariate genotypic models including additive and dominance genotypic effects and a genomic inbreeding covariate allowed us to retrieve the additive and dominance SNP variances for purebred and crossbred performances. These estimated variances were used, together with the allelic frequencies of the parental populations, to obtain additive and dominance variances in terms of genetic breeding values and dominance deviations. Estimates of additive genetic variances across traits were consistent with previous results without dominance indicating that additive and dominance genetic effects were non-confounded. Some traits showed relevant amount of dominance genetic variance in both populations (i.e. growth rate 8%, feed conversion ratio 9-12%, backfat thickness 14-12%, lean meat 10-8%, carcass lesions 9%, in purebreds and crossbreds, respectively) or increased amount in crossbreds (i.e. ham cut 8-13%, loin 7-16%, pH semimembranosus 13-18%, pH longissimus dorsi 9-14%, dressing yield 5-15%, androstenone 5-13% and estradiol 6-11%). Results suggest that accounting for dominance in the models of these traits could lead to an increased GEBV accuracy and that using crossbred information can be beneficial to evaluate purebred candidates to selection for crossbred performance. Further research will compare additive and dominance marker effects between crossbred and purebred performances. 

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2017

Estimación de la varianza aditiva y dominante en caracteres de cerdo medidos en población pura y cruzada usando G-GIBBS

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L. Tusell et al., XVII Jornadas sobre producción animal, AIDA-ITEA, Zaragoza, Espagne, 30-31 mai 2017, p. 450-452

La expresión fenotípica de ciertos caracteres de interés en producción puede estar influenciada por efectos genéticos no aditivos tales como la dominancia, responsable, en parte, de la heterosis existente dentro de línea y en cruzamiento. Incluir la dominancia en las evaluaciones genómicas de estos caracteres podría conllevar a un aumento en la precisión de la estima de los valores de cría a la vez que dar una idea del interés en utilizar informaciones de individuos cruzados para evaluar las líneas puras por su aptitud al cruzamiento. Este estudio tiene por objetivo estimar las contribuciones genéticas aditivas y de dominancia a la varianza fenotípica total de diversos caracteres de crecimiento y eficiencia alimentaria, composición de la canal, calidad de carne, comportamiento e indicadores de olor y madurez sexual medidos en cerdo de raza pura y en cruce.

ENG

Genomic estimation of dominance genetic variance in purebred and  crossbred pig performances

This study aims at assessing the contribution of the additive and dominance genomic variances to the phenotype expression of several purebred Piétrain and crossbred (Piétrain x Large White) pig performances. A total of 636 purebred and 720 crossbred male piglets were phenotyped for 22 traits that can be classified into growth rate and feed efficiency, carcass composition, meat quality, behavior, boar taint and puberty groups of traits. Additive and dominance variances estimated in univariate genotypic models including additive and dominance genotypic effects allowed us to retrieve the additive and dominance SNP variances. These ones were used, together with the allelic frequencies of the parental populations, to obtain additive and dominance variances in terms of genetic breeding values and dominance deviations. Some traits showed relevant amount of dominance genetic  variance in both populations (i.e. backfat thickness, pH) or increased amount in crossbreds (i.e. ham cut, loin and dressing yield) suggesting that accounting for dominance in the models of these traits could lead to an increased GEBV accuracy and that using crossbred information can be beneficial to evaluate purebred candidates to selection for crossbred performance.

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2017

Genome-wide association studies in purebred and crossbred entire male pigs

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Hélène Gilbert et al., 66th EAAP, 31 août- 04 septembre 2015, Varsovie, Pologne, session 45 : pigs genetics, visuel d'intervention

A total of 654 purebred Piétrain entire male pigs and 716 crossbred Piétrain × Large White entire male pigs issued from about 70 Piétrain sires were tested in a French test station for production traits (feed intake, feed efficiency, growth rate, carcass composition and meat quality). All were genotyped with the 60K Porcine SNPchip. Genome wide association studies were run using linear mixed models with a genomic kinship matrix to account for relatedness between individuals, and the fixed effect of each SNP was tested separately. In a first step, separate analyses of the two populations showed suggestive results (P<0.0001) for almost all traits in the two populations. For production traits, eight 1-Mb regions affected multiple correlated traits in the purebred pigs, and only one in the crossbred pigs. Only two regions with P<0.0001 were detected in common in purebred and crossbred individuals after correction for the halothane mutation, on SSC1 and SSC2. Breed differences in linkage disequilibrium between markers and causal variants, or different gene effects due to the purebred vs crossbred polygenic background could explain these discrepancies. Genotypes were phased and chromosome breed origins were identified in all progeny. Analyses were thus run to estimate within breed allelic effects in the crossbred population, and combining the two populations. After accounting for differences in allele frequencies in the two populations, only few SNP estimates showed significantly different allelic effects depending on the genetic background. If confirmed in a larger design, this suggests that genes affecting production traits act similarly in purebred and crossbred commercial pigs, as suggested by high genetic correlations between purebred and crossbred pigs for these traits.

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2017

Pedigree and genomic evaluation of pigs using a terminal cross model

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Tusell et al., 66th EAAP, Varsovie, Pologne, 31 aout-4 septembre 2015, visuels d'intervention

This study presents a single-step terminal-cross model (GEN) to estimate genetic parameters of growth rate and pH of longissimus dorsi in pigs. The model is compared in terms of parameter estimates and breeding value accuracies with a pedigree-based terminal-cross model (PED) and 2 univariate single-step models (GEN_UNI) for purebred (PB) and crossbred (CB) performance. Ninety Piétrain sires were mated with 306 Piétrain and 306 Large White dams leading a total of 654 PB and 716 CB male piglets. Sires and PB offspring were genotyped using the 60K SNP chip. PB and CB performances were jointly analyzed as 2 traits. The PB animals were accounted for through an animal model, whereas the additive genetic effect of a CB individual was decomposed into its sire and dam allelic contribution effects plus a Mendelian sampling confounded with the residual. Genetic correlation between the PB and the sire contribution for CB performance was estimated. The inverse of a matrix combining both genomic and pedigree relationship matrices was used in the mixed model equations for the Piétrain line as in a single-step procedure. The PED model was of the same form as GEN but accounted only for pedigree information. The GEN_UNI models contained same effects as the GEN model for either the PB or CB performance. (Co)variance components were estimated by Gibbs sampling. Genetic correlations [HPD95%] between PB and CB traits obtained with the GEN model were close to unity: 0.84 [0.45, 1.00] and 0.97 [0.83, 1.00] for growth rate and pH, respectively, suggesting that PB line selection is already successful to improve CB performance. Genotyped animals obtained higher breeding value accuracies with the GEN model than with the PED and GEN_UNI models. Accounting for PB and CB information together with genomic information improves the precision of the genetic evaluation in breeding programs based on crossbreeding.

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2017

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