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Lutz Bunger - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of single nucleotide polymorphisms variation associated with important economic and computed tomography measured traits in Texel Sheep.
    animal, 2017
    Co-Authors: D Garza Hernandez, Mucha S, Georgios Banos, Karolina Kaseja, Kl Moore, Nr Lambe, J Yates, Lutz Bunger
    Abstract:

    Sheep are an important part of the global agricultural economy. Growth and meat production traits are significant economic traits in Sheep. The Texel breed is the most popular terminal sire breed in the UK, mainly selected for muscle growth and lean carcasses. This is a study based on a genome-wide association approach that investigates the links between some economically important traits, including computed tomography (CT) measurements, and molecular polymorphisms in UK Texel Sheep. Our main aim was to identify single nucleotide polymorphisms (SNP) associated with growth, carcass, health and welfare traits of the Texel Sheep breed. This study used data from 384 Texel rams. Data comprised ten traits, including two CT measured traits. The phenotypic data were placed in four categories: growth traits, carcass traits, health traits and welfare traits. De-regressed estimated breeding values (EBV) for these traits together with sire genotypes derived with the Ovine 50 K SNP array of Illumina were jointly analysed in a genome wide association analysis. Eight novel chromosome-wise significant associations were found for carcass, growth, health and welfare traits. Three significant markers were intronic variants and the remainder intergenic variants. This study is a first step to search for genomic regions controlling CT-based productivity traits related to body and carcass composition in a terminal sire Sheep breed using a 50 K SNP genome-wide array. Results are important for the further development of strategies to identify causal variants associated with CT measures and other commercial traits in Sheep. Independent studies are needed to confirm these results and identify candidate genes for the studied traits.

  • The effects of different farm environments on the performance of Texel Sheep
    Animal, 2015
    Co-Authors: Mclaren A, Joanne Conington, Nr Lambe, Susan Brotherstone, Raphael A. Mrode, Lutz Bunger
    Abstract:

    In order to assess the extent of genotype by environment interactions (G×E) and environmental sensitivity in Sheep farm systems, environmental factors must be identified and quantified, after which the relationship with the traits(s) of interest can be investigated. The objectives of this study were to develop a farm environment (FE) scale, using a canonical correlation analysis, which could then be used in linear reaction norm models. Fine-scale farm survey data, collected from a sample of 39 Texel flocks across the United Kingdom, was combined with information available at the national level. The farm survey data included information on flock size and concentrate feed use. National data included flock performance averages for 21-week-old weight (21WT), ultrasound back-fat (UFD) and muscle (UMD) depths, as well as regional climatic data. The FE scale developed was then combined with 181 555 (21WT), 175 399 (UMD) and 175 279 (UFD) records from lambs born between 1990 and 2011, on 494 different Texel flocks, to predict reaction norms for sires used within the population. A range of sire sensitivities estimated across the FE scale confirmed the presence of genetic variability as both 'plastic' and 'robust' genotypes were observed. Variations in heritability estimates were also observed indicating that the rate genetic progress was dependent on the environment. Overall, the techniques and approaches used in this study have proven to be useful in defining Sheep FEs. The results observed for 21WT, UMD and UFD, using the reaction norm models, indicate that in order to improve genetic gain and flock efficiency, future genetic evaluations would benefit by accounting for the G×E observed.

  • Genome-wide association study of footrot in Texel Sheep
    Genetics Selection Evolution, 2015
    Co-Authors: Sebastian Mucha, Lutz Bunger, Joanne Conington
    Abstract:

    Background This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. Methods This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Results Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r^2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Conclusions Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

  • Genome-wide association study of footrot in Texel Sheep
    Genetics Selection Evolution, 2015
    Co-Authors: Sebastian Mucha, Lutz Bunger, Joanne Conington
    Abstract:

    This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

  • Genome-wide association study of footrot in
    2015
    Co-Authors: Mucha S, Lutz Bunger, Joanne Conington
    Abstract:

    Background: This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. Methods: This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Results: Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r 2 at ad istance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Conclusions: Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

Carole Charlier - One of the best experts on this subject based on the ideXlab platform.

  • Demonstrating polymorphic miRNA-mediated gene regulation in vivo: application to the g+6223G->A mutation of Texel Sheep.
    RNA, 2010
    Co-Authors: Haruko Takeda, Carole Charlier, Frédéric Farnir, Michel Georges
    Abstract:

    We herein describe the development of a biochemical method to evaluate the effect of single nucleotide polymorphisms (SNPs) in target genes on their regulation by microRNAs in vivo. The method is based on the detection of allelic imbalance in RNAs coimmunoprecipitated with AGO proteins from tissues of heterozygous individuals. We characterize the performances of our approach using a model system in a cell culture, and then apply it successfully to prove that the 3′UTR g+6223G→A mutation operates by promoting RISC-dependent down-regulation of myostatin (MSTN) in skeletal muscle of Texel Sheep.

  • A mutation creating a potential illegitimate microRNA target site in the myostatin gene affects muscularity in Sheep.
    Nature genetics, 2006
    Co-Authors: Florian Caiment, Xavier Tordoir, Elisabeth Laville, Jacques Bouix, Francis Eychenne, Michel Georges, Catherine Larzul, Dimitri Pirottin, Albert Clop, Haruko Takeda, James Tobin, Carole Charlier, Françoise Meish, Fabienne Marcq, Bernard Bibé, Jean-michel Elsen, Dusanka Milenkovic
    Abstract:

    Texel Sheep are renowned for their exceptional meatiness. To identify the genes underlying this economically important feature, we performed a whole-genome scan in a Romanov x Texel F2 population. We mapped a quantitative trait locus with a major effect on muscle mass to chromosome 2 and subsequently fine-mapped it to a chromosome interval encompassing the myostatin (GDF8) gene. We herein demonstrate that the GDF8 allele of Texel Sheep is characterized by a G to A transition in the 3' UTR that creates a target site for mir1 and mir206, microRNAs (miRNAs) that are highly expressed in skeletal muscle. This causes translational inhibition of the myostatin gene and hence contributes to the muscular hypertrophy of Texel Sheep. Analysis of SNP databases for humans and mice demonstrates that mutations creating or destroying putative miRNA target sites are abundant and might be important effectors of phenotypic variation.

  • The callipyge mutation and other genes that affect muscle hypertrophy in Sheep.
    Genetics, selection, evolution : GSE, 2005
    Co-Authors: Noelle Cockett, Maria Smit, Tracy Hadfield, Gary Snowder, Karin Segers, Christopher A Bidwell, Michel Georges, Carole Charlier
    Abstract:

    Genetic strategies to improve the profitability of Sheep operations have generally focused on traits for reproduction. However, natural mutations exist in Sheep that affect muscle growth and development, and the exploitation of these mutations in breeding strategies has the potential to significantly improve lamb-meat quality. The best-documented mutation for muscle development in Sheep is callipyge (CLPG), which causes a postnatal muscle hypertrophy that is localized to the pelvic limbs and loin. Enhanced skeletal muscle growth is also observed in animals with the Carwell (or rib-eye muscling) mutation, and a double-muscling phenotype has been documented for animals of the Texel Sheep breed. However, the actual mutations responsible for these muscular hypertrophy phenotypes in Sheep have yet to be identified, and further characterization of the genetic basis for these phenotypes will provide insight into the biological control of muscle growth and body composition.

Nr Lambe - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of single nucleotide polymorphisms variation associated with important economic and computed tomography measured traits in Texel Sheep.
    animal, 2017
    Co-Authors: D Garza Hernandez, Mucha S, Georgios Banos, Karolina Kaseja, Kl Moore, Nr Lambe, J Yates, Lutz Bunger
    Abstract:

    Sheep are an important part of the global agricultural economy. Growth and meat production traits are significant economic traits in Sheep. The Texel breed is the most popular terminal sire breed in the UK, mainly selected for muscle growth and lean carcasses. This is a study based on a genome-wide association approach that investigates the links between some economically important traits, including computed tomography (CT) measurements, and molecular polymorphisms in UK Texel Sheep. Our main aim was to identify single nucleotide polymorphisms (SNP) associated with growth, carcass, health and welfare traits of the Texel Sheep breed. This study used data from 384 Texel rams. Data comprised ten traits, including two CT measured traits. The phenotypic data were placed in four categories: growth traits, carcass traits, health traits and welfare traits. De-regressed estimated breeding values (EBV) for these traits together with sire genotypes derived with the Ovine 50 K SNP array of Illumina were jointly analysed in a genome wide association analysis. Eight novel chromosome-wise significant associations were found for carcass, growth, health and welfare traits. Three significant markers were intronic variants and the remainder intergenic variants. This study is a first step to search for genomic regions controlling CT-based productivity traits related to body and carcass composition in a terminal sire Sheep breed using a 50 K SNP genome-wide array. Results are important for the further development of strategies to identify causal variants associated with CT measures and other commercial traits in Sheep. Independent studies are needed to confirm these results and identify candidate genes for the studied traits.

  • The effects of different farm environments on the performance of Texel Sheep
    Animal, 2015
    Co-Authors: Mclaren A, Joanne Conington, Nr Lambe, Susan Brotherstone, Raphael A. Mrode, Lutz Bunger
    Abstract:

    In order to assess the extent of genotype by environment interactions (G×E) and environmental sensitivity in Sheep farm systems, environmental factors must be identified and quantified, after which the relationship with the traits(s) of interest can be investigated. The objectives of this study were to develop a farm environment (FE) scale, using a canonical correlation analysis, which could then be used in linear reaction norm models. Fine-scale farm survey data, collected from a sample of 39 Texel flocks across the United Kingdom, was combined with information available at the national level. The farm survey data included information on flock size and concentrate feed use. National data included flock performance averages for 21-week-old weight (21WT), ultrasound back-fat (UFD) and muscle (UMD) depths, as well as regional climatic data. The FE scale developed was then combined with 181 555 (21WT), 175 399 (UMD) and 175 279 (UFD) records from lambs born between 1990 and 2011, on 494 different Texel flocks, to predict reaction norms for sires used within the population. A range of sire sensitivities estimated across the FE scale confirmed the presence of genetic variability as both 'plastic' and 'robust' genotypes were observed. Variations in heritability estimates were also observed indicating that the rate genetic progress was dependent on the environment. Overall, the techniques and approaches used in this study have proven to be useful in defining Sheep FEs. The results observed for 21WT, UMD and UFD, using the reaction norm models, indicate that in order to improve genetic gain and flock efficiency, future genetic evaluations would benefit by accounting for the G×E observed.

  • Effect and mode of action of the Texel muscling QTL (TM-QTL) on carcass traits in purebred Texel lambs.
    Animal, 2014
    Co-Authors: J.m. Macfarlane, Nr Lambe, Oswald Matika, Stephen Bishop, William Haresign, P. L. Johnson, B. T. Wolf, Lutz Bunger
    Abstract:

    TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel Sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel Sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P

  • Prediction of intramuscular fat levels in Texel lamb loins using X-ray computed tomography scanning
    Meat Science, 2014
    Co-Authors: N. Clelland, Lutz Bunger, Joanne Conington, K.a. Mclean, C. A. Maltin, Sara Knott, Nr Lambe
    Abstract:

    For the consumer, tenderness, juiciness and flavour are often described as the most important factors for meat eating quality, all of which have a close association with intramuscular fat (IMF). X-ray computed tomography (CT) can measure fat, muscle and bone volumes and weights, in vivo in Sheep and CT predictions of carcass composition have been used in UK Sheep breeding programmes over the last few decades. This study aimed to determine the most accurate combination of CT variables to predict IMF percentage of M. longissimus lumborum in Texel lambs. As expected, predicted carcass fat alone accounted for a moderate amount of the variation (R(2)=0.51) in IMF. Prediction accuracies were significantly improved (Adj R(2)>0.65) using information on fat and muscle densities measured from three CT reference scans, showing that CT can provide an accurate prediction of IMF in the loin of purebred Texel Sheep.

  • The effect of the Texel Muscling QTL on live and carcass weight in Texel lambs
    Small Ruminant Research, 2012
    Co-Authors: J.m. Macfarlane, Nr Lambe, William Haresign, Lutz Bunger
    Abstract:

    Abstract The Texel Muscling QTL (TM-QTL) is a QTL affecting loin muscling in Texel Sheep with a paternal polar overdominant pattern of expression. This study on purebred Texel Sheep used the first available data to include homozygote TM-QTL carriers in addition to homozygote non-carriers and both heterozygotes to assess the effect of TM-QTL on live weight throughout growth from birth to slaughter (at around 20 weeks of age) and carcass weight. TM-QTL was found to have an effect on most measures of live and carcass weight. Animals inheriting two copies of TM-QTL showed an increase of 1.5 kg or 9% in carcass weight and an increase in live weight across a range of ages from birth to slaughter of between 7 and 15% compared to animals carrying no copies of TM-QTL. The effect of TM-QTL on the weight traits studied appears to be additive but heterozygote weights did not always support this. If more data on lambs carrying TM-QTL become available in future it would be useful to validate this effect on live and carcass weight and the pattern of the effect.

Joanne Conington - One of the best experts on this subject based on the ideXlab platform.

  • The effects of different farm environments on the performance of Texel Sheep
    Animal, 2015
    Co-Authors: Mclaren A, Joanne Conington, Nr Lambe, Susan Brotherstone, Raphael A. Mrode, Lutz Bunger
    Abstract:

    In order to assess the extent of genotype by environment interactions (G×E) and environmental sensitivity in Sheep farm systems, environmental factors must be identified and quantified, after which the relationship with the traits(s) of interest can be investigated. The objectives of this study were to develop a farm environment (FE) scale, using a canonical correlation analysis, which could then be used in linear reaction norm models. Fine-scale farm survey data, collected from a sample of 39 Texel flocks across the United Kingdom, was combined with information available at the national level. The farm survey data included information on flock size and concentrate feed use. National data included flock performance averages for 21-week-old weight (21WT), ultrasound back-fat (UFD) and muscle (UMD) depths, as well as regional climatic data. The FE scale developed was then combined with 181 555 (21WT), 175 399 (UMD) and 175 279 (UFD) records from lambs born between 1990 and 2011, on 494 different Texel flocks, to predict reaction norms for sires used within the population. A range of sire sensitivities estimated across the FE scale confirmed the presence of genetic variability as both 'plastic' and 'robust' genotypes were observed. Variations in heritability estimates were also observed indicating that the rate genetic progress was dependent on the environment. Overall, the techniques and approaches used in this study have proven to be useful in defining Sheep FEs. The results observed for 21WT, UMD and UFD, using the reaction norm models, indicate that in order to improve genetic gain and flock efficiency, future genetic evaluations would benefit by accounting for the G×E observed.

  • Genome-wide association study of footrot in Texel Sheep
    Genetics Selection Evolution, 2015
    Co-Authors: Sebastian Mucha, Lutz Bunger, Joanne Conington
    Abstract:

    Background This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. Methods This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Results Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r^2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Conclusions Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

  • Genome-wide association study of footrot in Texel Sheep
    Genetics Selection Evolution, 2015
    Co-Authors: Sebastian Mucha, Lutz Bunger, Joanne Conington
    Abstract:

    This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

  • Genome-wide association study of footrot in
    2015
    Co-Authors: Mucha S, Lutz Bunger, Joanne Conington
    Abstract:

    Background: This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel Sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. Methods: This study used data from animals selected from a footrot-phenotyped Texel Sheep population of 2229 Sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Results: Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r 2 at ad istance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Conclusions: Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

  • Prediction of intramuscular fat levels in Texel lamb loins using X-ray computed tomography scanning
    Meat Science, 2014
    Co-Authors: N. Clelland, Lutz Bunger, Joanne Conington, K.a. Mclean, C. A. Maltin, Sara Knott, Nr Lambe
    Abstract:

    For the consumer, tenderness, juiciness and flavour are often described as the most important factors for meat eating quality, all of which have a close association with intramuscular fat (IMF). X-ray computed tomography (CT) can measure fat, muscle and bone volumes and weights, in vivo in Sheep and CT predictions of carcass composition have been used in UK Sheep breeding programmes over the last few decades. This study aimed to determine the most accurate combination of CT variables to predict IMF percentage of M. longissimus lumborum in Texel lambs. As expected, predicted carcass fat alone accounted for a moderate amount of the variation (R(2)=0.51) in IMF. Prediction accuracies were significantly improved (Adj R(2)>0.65) using information on fat and muscle densities measured from three CT reference scans, showing that CT can provide an accurate prediction of IMF in the loin of purebred Texel Sheep.

Torres Sweeney - One of the best experts on this subject based on the ideXlab platform.

  • major histocompatibility complex drb1 gene its role in nematode resistance in suffolk and Texel Sheep breeds
    Parasitology, 2005
    Co-Authors: G. Sayers, J.p. Hanrahan, Barbara Good, M. T. Ryan, J M Angles, Torres Sweeney
    Abstract:

    A potential control strategy for nematode infection in Sheep is the implementation of a breeding programme to select for genes associated with resistance. The Texel breed is more resistant to gastrointestinal nematode infection than the Suffolk breed, based on faecal egg count, and this difference should enable the identification of some of the genes responsible for resistance. The objective of this study was to determine if variation at the ovine MHC-DRB1 locus was associated with variation in faecal egg count in Suffolk and Texel Sheep. Ovar-DRB1 alleles and faecal egg count were determined for Texel (n = 105) and Suffolk (n = 71) lambs. Eight Ovar-DRB1 alleles, including 1 previously unknown allele, were identified in the Texel breed by sequence-base-typing. Seven Ovar-DRB1 alleles were identified in the Suffolk breed. Two Ovar-DRB1 alleles were common to both breeds, but were among the least frequent in the Suffolk population. In the Suffolk breed 1 Ovar-DRB1 allele was associated with a decrease in faecal egg count and 2 alleles with an increase in faecal egg count. This locus accounted for 14% of the natural variation in faecal egg count in Suffolks. There was no evidence for an association between Ovar-DRB1 alleles and faecal egg count in the Texel breed and the Ovar-DRB1 locus accounted for only 3% of the phenotypic variation in faecal egg count. These results suggest that the Ovar-DRB1 gene plays an important role in resistance to nematode infection in the Suffolk breed. The difference in faecal egg counts between these breeds may be attributable in part to the different allele profile at the Ovar-DRB1 locus.

  • Intron 1 of the interferon γ gene: Its role in nematode resistance in Suffolk and Texel Sheep breeds
    Research in Veterinary Science, 2005
    Co-Authors: G. Sayers, Barbara Good, James P. Hanrahan, M. T. Ryan, Torres Sweeney
    Abstract:

    Genetic variation at intron 1 of the interferon gamma gene has recently been associated with variation in faecal egg count in Romney, Merino and Soay breeds of Sheep. The Texel breed is more resistant to gastrointestinal nematode infection than the Suffolk breed, based on faecal egg count. Hence, the objective of this experiment was to characterise the polymorphisms of intron 1 of the interferon gammagene in Suffolk and Texel Sheep, and to determine if the characterised haplotype variants were associated with faecal egg count variation in these breeds. Intron 1 haplotypes and faecal egg measurements were determined for Suffolks (n=113) and Texels (n=135). Four haplotypes were identified in Suffolks (A, B, C and D), two haplotypes as previously described, and two previously unknown haplotypes. However, there was no association between interferon gamma intron 1 haplotype and faecal egg count in Suffolks. In contrast, two previously identified haplotypes (A and B) were present in the Texel breed, and the B haplotype was associated with resistance to nematode infection (P=0.02). These results suggest that intron 1 of the interferon gamma gene has an important role in resistance to nematode infection in the Texel breed.

  • Analysis of DRB1 exon 2 genotyping by STR size analysis in Suffolk and Texel Sheep breeds
    Irish Journal of Agricultural and Food Research, 2004
    Co-Authors: G. Sayers, Michael J. Stear, James P. Hanrahan, M. T. Ryan, S. Mitchel, Torres Sweeney
    Abstract:

    Alleles of the DRB1 exon 2 locus of the major histocompatibility complex have recently been associated with genetic resistance to gastrointestinal nematodes in Sheep. While sequence-based typing is the standard method for allele discrimination, a rapid, high throughput method for DRB1 exon 2 genotyping is required if such information is to be incorporated into national breeding programmes. Previous studies have highlight ed a simple tandem repeat (STR) located within intron 2 of the DRB1 gene, which could potentially be used to accurately assess the allele present within the adjacent exon 2. The aims of this study were firstly to compare two methods of STR analysis, Genescan and autoradiography, and secondly to investigate if STR analysis of DRB1 intron 2 could be used to accurately assess the profile of DRB1 exon 2. Six DRB1 exon 2 alleles were identified by sequence-based typing in Suffolk (n = 31) and eight in Texel (n = 60) Sheep. The results indicated that Genescan was a more accurate method of STR analysis than autoradiography. The expected 1:1 correspondence between STR size, analysed by Genescan and DRB1 exon 2 allele, determined by sequence-based typing, was not observed. However, the correspondence was found to be degenerate, whereby some alleles were associated with two STR sizes. Thus, irrespective of the STR size identified, STR analysis by Genescan identified the correct allele in all cases within both populations of animals studied. However, the Genescan method of allele identification cannot be used for Suffolk x Texel crossbred progeny or in other breeds where the relationship between STR size and DRB1 exon 2 allele is not known.