Production Traits In Sheep Research Articles

Pleiotropic Gene HMGA2 Regulates Myoblast Proliferation and Affects Body Size of Sheep.

Uncovering genes associated with muscle growth and body size will benefit the molecular breeding of meat Hu sheep. HMGA2 has proven to be an important gene in mouse muscle growth and is associated with the body size of various species. However, its roles in sheep are still limited. Using sheep myoblast as a cell model, the overexpression of HMGA2 significantly promoted sheep myoblast proliferation, while interference with HMGA2 expression inhibited proliferation, indicated by qPCR, EdU, and CCK-8 assays. Furthermore, the dual-luciferase reporter system indicated that the region NC_056056.1: 154134300-154134882 (-618 to -1200 bp upstream of the HMGA2 transcription start site) was one of the habitats of the HMGA2 core promoter, given the observation that this fragment led to a ~3-fold increase in luciferase activity. Interestingly, SNP rs428001129 (NC_056056.1:g.154134315 C>A) was detected in this fragment by Sanger sequencing of the PCR product of pooled DNA from 458 crossbred sheep. This SNP was found to affect the promoter activity and was significantly associated with chest width at birth and two months old, as well as chest depth at two and six months old. The data obtained in this study demonstrated the phenotypic regulatory role of the HMGA2 gene in sheep production traits and the potential of rs428001129 in marker-assisted selection for sheep breeding in terms of chest width and chest depth.

Novel pathways linked to the expression of temperament in Merino sheep: a genome-wide association study

Animal temperament refers to the inherent behavioural and emotional characteristics of an animal, influencing how it interacts with its environment. The selection of sheep for temperament can change the temperament traits of the selected line and improve the welfare and production (reproduction, growth, immunity) of those animals. To understand the genetics that underly variation in temperament in sheep, and how selection on temperament can affect other production traits, a genome-wide association study was carried out. Merino sheep from lines selected for traits of calm and nervous temperament, and a commercial population, on which the temperament traits had never been assessed, were used. Blood samples from the three populations were genotyped using an Illumina GGP Ovine 50 K Genotyping BeadChip. The calm and nervous populations in the selected lines presented as distinct genetic populations, and 2 729 of the 45 761 single nucleotide polymorphisms (SNPs) had significantly different proportions between the two lines. Of those 2 729 SNPs, 2 084 were also associated with temperament traits in the commercial population. A genomic annotation identified 81 candidate genes for temperament, nearly half of which are associated with disorders of social behaviour in humans. Five of those 81 candidate genes are related to production traits in sheep. Two genes were associated with personality disorders in humans and with production traits in sheep. We identified significant enrichment in genes involved in nervous system processes such as the regulation of systemic arterial blood pressure, ventricular myocyte action, multicellular organismal signalling, ion transmembrane transport, and calcium ion binding, suggesting that temperament is underpinned by variation in multiple biological systems. Our results contribute to understanding of the genetic basis of animal temperament which could be applied to the genetic evaluation of temperament in sheep and other farm animals.

Examining across year genotype by environment interactions for production and reproduction traits in Merino sheep

Variation in feed resource availability within production systems can cause genotype by environment interactions that change the ranking of the best animals to select between environments. Mediterranean environments have high variation in pasture growth between years that could cause genetic by environment interactions for sheep production traits. Therefore, we estimated heritabilities for live weight, fleece weight, fibre diameter and number of lambs weaned in six years from 2000 to 2005 and correlations between years comparing multivariate analysis and random regression analysis. We compared 3 methods: 1 multivariate analysis estimating (co)variances for traits in each year, 2 Random regression estimated (co)variances for intercept and slope for traits as repeated measurements fitted against average pasture growth in each year and 3. Random regression fitted against corrected average performance of animals in each year. Random regression was estimated with an order of polynomial of one for additive genetic variance and zero for permanent environmental effects. This combination of polynomials was the best fit based on Bayesian information criterion. We estimated heritabilities for each year and correlations between years using records from 3299 pedigreed Merino ewes managed at Katanning in Western Australia. There were 4651 records for adult live weight, 6750 for adult clean fleece weight, 6965 for adult fibre diameter, and 7774 for number of lambs weaned across all 6 years. Number of lambs weaned had more genotype by environment interactions than other traits, with fibre diameter and fleece weight having genotype by environment interactions between only a few years. Based on Bayesian information criterion values, multivariate analysis fit the data better for live weight, fleece weight and fibre diameter. Additionally, random regression estimated higher genetic correlations between years than multivariate analysis suggesting there was not enough flexibility in the random regression analysis, which used only first order polynomials, to fit differences between years. Pasture growth across years did not explain differences in performance for traits across years. Therefore, for number of lambs weaned, random regression using corrected average performance was a better fit than average pasture growth. For other traits, more years or a better indicator of variation in performance within and between years are required to use random regression for genotype by environment interactions.

Epigenetic regulation of functional candidate genes for milk production traits in dairy sheep subjected to protein restriction in the prepubertal stage

BackgroundAs the prepubertal stage is a crucial point for the proper development of the mammary gland and milk production, this study aims to evaluate how protein restriction at this stage can affect methylation marks in milk somatic cells. Here, 28 Assaf ewes were subjected to 42.3% nutritional protein restriction (14 animals, NPR) or fed standard diets (14 animals, C) during the prepubertal stage. During the second lactation, the milk somatic cells of these ewes were sampled, and the extracted DNA was subjected to whole-genome bisulfite sequencing.ResultsA total of 1154 differentially methylated regions (DMRs) were identified between the NPR and C groups. Indeed, the results of functional enrichment analyses of the genes harboring these DMRs suggested their relevant effects on the development of the mammary gland and lipid metabolism in sheep. The additional analysis of the correlations of the mean methylation levels within these DMRs with fat, protein, and dry extract percentages in the milk and milk somatic cell counts suggested associations between several DMRs and milk production traits. However, there were no phenotypic differences in these traits between the NPR and C groups.ConclusionIn light of the above, the results obtained in the current study might suggest potential candidate genes for the regulation of milk production traits in the sheep mammary gland. Further studies focusing on elucidating the genetic mechanisms affected by the identified DMRs may help to better understand the biological mechanisms modified in the mammary gland of dairy sheep as a response to nutritional challenges and their potential effects on milk production.

Predicting feed efficiency traits in growing lambs from their ruminal microbiota

Selecting feed-efficient sheep could improve the sustainability of this livestock production. However, most sheep breeding companies cannot afford to record feed intake to select feed-efficient animals. Past studies underlined the potential of omics data, including microbiota metabarcoding data, as proxies for feed efficiency. The study involved 277 Romane lambs from two lines divergently selected for residual feed intake (RFI). There were two objectives: check the consequences of selecting for feed efficiency over the rumen microbiota, and assess the predictive ability of the rumen microbiota for host traits. The study assessed two contrasting diets (concentrate diet and mixed diet) and two microbial groups (prokaryotes and eukaryotes). Discriminant analyses did not highlight any significant effect of sheep selection for residual feed intake on the rumen microbiota composition. Indeed, prokaryotic and eukaryotic microbiota compositions poorly discriminated the RFI lines, with averaged balanced error rates ranging from 45% to 55%. Correlations between host traits (feed efficiency and production traits) and their predictions from microbiota data varied between −0.07 and 0.56, depending on the trait, diet and sequencing. Feed intake was the most accurately predicted trait. However, predictions from fixed effects and BW were more accurate than or as accurate as predictions from the microbiota. Environmental effects can greatly affect the variability of microbiota compositions. Considering batch and environmental effects should be paramount when the predictive ability of the microbiota is assessed. This study argues why metabarcoding the rumen microbiota is not the best way to predict meat sheep production traits: fixed effects and BW were more cost-effective proxies and they led to similar or better predictive accuracies than microbiota metabarcoding (16S and 18S sequencing).

Effect of Skin wrinkles on production traits in sheep: An overview

Effect of Skin wrinkles on production traits in sheep: An overview

Detection of candidate genes affecting milk production traits in sheep using whole-genome sequencing analysis.

BackgroundArtificial and natural selection for important economic traits and genetic adaptation of the populations to specific environments have led to the changes on the sheep genome. Recent advances in genome sequencing methods have made it possible to use comparative genomics tools to identify genes under selection for traits of economic interest in domestic animals.ObjectivesIn this study, we compared the genomes of Assaf and Awassi sheep breeds with those of the Cambridge, Romanov and British du cher sheep breeds to explore positive selection signatures for milk traits using nucleotide diversity (Pi) and FST statistical methods.MethodsGenome sequences from fourteen sheep with a mean sequence depth of 9.32X per sample were analysed, and a total of 23 million single nucleotide polymorphisms (SNPs) were called and applied for this study. Genomic clustering of breeds was identified using ADMIXTURE software. The FST and Pi values for each SNP were computed between population A (Assaf and Awassi) and population B (Cambridge, British du cher, and Romanov).ResultsThe results of the PCA grouped two classes for these five dairy sheep breeds. The selection signatures analysis displayed 735 and 515 genes from FST and nucleotide diversity (Pi) statistical methods, respectively. Among all these, 12 genes were shared between the two approaches. The most conspicuous genes were related to milk traits, including ST3GAL1 (the synthesis of oligosacáridos), CSN1S1 (milk protein), CSN2 (milk protein), OSBPL8 (fatty acid traits), SLC35A3 (milk fat and protein percentage), VPS13B (total milk production, fat yield, and protein yield), DPY19L1 (peak yield), CCDC152 (lactation persistency and somatic cell count), NT5DC1 (lactation persistency), P4HTM (test day protein), CYTH4 (FAT Production) and METRNL (somatic cell), U1 (milk traits), U6 (milk traits) and 5S_RRNA (milk traits).ConclusionsThe findings provide new insight into the genetic basis of sheep milk properties and can play a role in designing sheep breeding programs incorporating genomic information.

Detection of genomic regions underlying milk production traits in Valle del Belice dairy sheep using regional heritability mapping.

The aim of this study was to identify genomic regions underlying milk production traits in the Valle del Belice dairy sheep using regional heritability mapping (RHM). Repeated measurements for milk yield (MY), fat percentage and yield (F% and FY) and protein percentage and yield (P% and PY), collected over a period of 6 years (2006–2012) on 481 Valle del Belice ewes, were used for the analysis. Animals were genotyped with the Illumina 50k SNP chip. Variance components, heritabilities and repeatabilities within and across lactations were estimated, fitting parity, litter size, season of lambing and fortnights in milk, as fixed; and additive genetic, permanent environment within and across lactations, flock by test‐day interaction and residual as random effects. For the RHM analysis, the model included the same fixed and random effects as before, plus an additional regional genomic additive effect (specific for the region being tested) as random. While the whole genomic additive effect was estimated using the genomic relationship matrix (GRM) constructed from all SNPs, the regional genomic additive effect was estimated from a GRM matrix constructed from the SNPs within each region. Heritability estimates ranged between 0.06 and 0.15, with repeatabilities being between 0.14 and 0.24 across lactations and between 0.23 and 0.39 within lactation for all milk production traits. A substantial effect of flock‐test‐day on milk production traits was also estimated. Significant genomic regions at either genome‐wide (p < .05) or suggestive (i.e., one false positive per genome scan) level were identified on chromosome (OAR) 2, 3 and 20 for F% and on OAR3 for P%, with the regions on OAR3 in common between the two traits. Our results confirmed the role of LALBA and AQP genes, on OAR3, as candidate genes for milk production traits in sheep.

Genome-wide comparative analyses reveal selection signatures underlying adaptation and production in Tibetan and Poll Dorset sheep

The identification of genome-wide selection signatures can provide insights on the mechanisms of natural and/or artificial selection and uncover genes related to biological functions and/or phenotypes. Tibetan sheep are an important livestock in Tibet, providing meat and wool for Tibetans who are renown for breeding livestock that adapt well to high altitudes. Using whole-genome sequences with an effective sequencing depth of 5×, we investigated the genomic diversity and structure and, identified selection signatures of White Tibetan, Oula and Poll Dorset sheep. We obtained 30,163,679 Single Nucleotide Polymorphisms (SNPs) and 5,388,372 indels benchmarked against the ovine Oar_v4.0 genome assembly. Next, using FST, ZHp and XP-EHH approaches, we identified selection signatures spanning a set of candidate genes, including HIF1A, CAPN3, PRKAA1, RXFP2, TRHR and HOXA10 that are associated with pathways and GO categories putatively related to hypoxia responses, meat traits and disease resistance. Candidate genes and GO terms associated with coat color were also identified. Finally, quantification of blood physiological parameters, revealed higher levels of mean corpuscular hemoglobin measurement and mean corpuscular hemoglobin concentration in Tibetan sheep compared with Poll Dorset, suggesting a greater oxygen-carrying capacity in the Tibetan sheep and thus better adaptation to high-altitude hypoxia. In conclusion, this study provides a greater understanding of genome diversity and variations associated with adaptive and production traits in sheep.

PSV-30 Influence of crossbreeding on meat production, growth, meat quality, and carcass traits within sheep fed the same diet

Abstract The aim of this study was to determine the effect of crossbreeding on meat production traits of sheep. Purebred (Volgograd breed, n = 30) and crossbred (F3, Volgograd x ¼ North Caucasian breed, n=30) sheep were fed for 60 days from the age of 8 months. The diet was the same for both groups and included: a dry fodder of mixed herbs, green-cut fodder, stock feed of barley, and salt. The initial liveweight for purebred sheep was 42.39±0.38 kg and for crossbred sheep was 44.41±0.47 kg (P &amp;lt; 0.01). The final liveweight for purebred sheep was 50.10±0.43 kg. Crossbred sheep were heavier at 52.40±0.36 kg (P &amp;lt; 0.001). The weight of carcasses was greater for crossbred sheep at 22.87±0.53 kg (P &amp;lt; 0.05) and 20.67±0.76 kg for purebred sheep. Compared with purebred sheep, crossbred sheep had a lower amount of internal fat (0.92±0.27 kg vs. 1.18±0.35 kg). The weight of meat from purebred sheep was less than crossbred sheep (16.12±0.63 kg vs. 18.28±0.43 kg, P &amp;lt; 0.05) while the weight of bone was almost the same (4.55 vs. 4.59 kg). Consequently, the ratio of meat/bone was 5.54 vs. 3.98. The food energy value for the meat of purebred sheep was greater at 259.36±16.78 kcal than the meat of crossbred sheep at 233.85±11.10 kcal. Total moisture in the meat of purebred sheep was lower (60.11±0.67 vs. 63.05±0.65, P &amp;lt; 0.05), total protein was a little higher (17.71±0.77 vs. 17.63±0.24), and lipids were higher (20.73±0.73 vs. 17.89±0.82, P &amp;lt; 0.05) than in the meat of crossbred sheep. The meat of purebred sheep had a lower concentration of non-replaceable amino acid (12.47 g) compared with meat of crossbred sheep (17.20 g), and a lower concentration of replaceable amino acid (23.08 g vs. 26.84 g). The results of this study can be used to improve meat production and meat quality.

Distribution of JAK2 genotypes across Suffolk and Pomeranian sheep

• JAK2 kinase belongs primarily to the signal pathways of STAT (Signal Transducer and Activator of Transcription) proteins. • JAK2 participates in the transmission of signals of extracellular growth factors, cytokines and hormones. • The discovered polymorphisms may affect the transcription process of the JAK2 gene. • Introns are functionally active participants in the function of genes and genomes. In recent years, the improvement of sheep production traits has met with great interest from breeders. A significant effect of the JAK2 gene encoding Janus kinase 2 on growth and reproductive parameters in different animal species has been confirmed. The aim of the present study was to identify new polymorphic sites in the ovine JAK2 gene. Three single nucleotide polymorphisms (SNPs) have been identified using the Sanger sequencing method. The first and the second variant were located in exon 6 (R1 = g.72850860 G > A; rs160146162; R2 = g.72850917A > G; rs160146160). The third SNP was located in intron 22 proximal to exon 23 (R3 = g.72895034 G > A; rs429445187). A total of 98 individuals from two breeds (Pomeranian, n = 64 and Suffolk, n = 39) were genotyped. They were kept on an organic farm located in the West Pomeranian Province. In the case of the g.72850860 G > A polymorphism, the A allele and the AA genotype were the least frequent in the Pomeranian breed. Fifteen percent of animals had the AA genotype, whereas this genotype was not detected in the Suffolk breed. The GG genotype was the most frequent in the Suffolk breed (84.85 %), while heterozygotes were predominant in the Pomeranian breed (45 %). Allele and genotype frequencies of the g.72850917A > G polymorphism were similar in both breeds, in which the AG genotype was predominant (54.5 % and 46.7 % for Suffolk and Pomeranian, respectively). Also, allele and genotype frequencies of an intronic polymorphism were similar in both breeds, in which heterozygotes were the most common (52.3 % and 65.7 % for Pomeranian and Suffolk, respectively). The results of the present study could be used for the further association analysis of selected performance traits in connection with the described polymorphisms.

Single nucleotide polymorphism of the β-lactoglobulin gene in sheep breeds reared in Bulgaria

In the present study, single nucleotide polymorphism in exon II of the β-lactoglobulin gene was investigated in four Bulgarian sheep breeds: Bulgarian Dairy Synthetic Population sheep (BDSP), Copper-red Shumen sheep (CRSH), Stara Zagora sheep (STZG) and Pleven Blackhead sheep (PLBH). Two genetic variants of β-LG gene (A and B) have been identified through PCR-RFLP assay. A 103 bp fragment of the polymorphic β-LG locus were amplified and digested with endonuclease enzyme RsaI. The obtained restriction fragments revealed three genotypes: AA, AB and BB, observed in 31%, 65.5% and 3.5% of the BDSP population and in 48%, 28% and 24% of CRSH sheep population, respectively, with departure from the Hardy-Weinberg equilibrium (P&lt;0.05) in these groups. The allele frequencies demonstrated a prevalence of the A allele (0.638 and 0.620) over the B allele (0.362 and 0.380) in both populations. On the contrary, the distribution of allele frequencies in STZG and PLBH was 0.240 and 0.100 for allele A, respectively and 0.760 and 0.900 for allele B. Therefore, the homozygous BB genotype in these sheep populations was more frequently encountered (0.520 and 0.800) than the heterozygous AB genotype (0.480 and 0.200), with HWE correspondence (P&gt;0.1). The homozygous genotype AA was absent in STZG and PLBH sheep populations. The greatest Nei’s genetic distance calculated by UPGMA method was found between the populations BDSPand PLBH (0.5334), while the closest relationship (0.0006) was established between CRSH and BDSP. The results obtained from the present investigation confirmed the presence of the SNP polymorphism in exon II of the β-lactoglobulin gene. Therefore, the genetic variability established in this polymorphic locus could be applied in further association studies with milk production traits in sheep.

Genomic prediction based on selected variants from imputed whole-genome sequence data in Australian sheep populations

BackgroundWhole-genome sequence (WGS) data could contain information on genetic variants at or in high linkage disequilibrium with causative mutations that underlie the genetic variation of polygenic traits. Thus far, genomic prediction accuracy has shown limited increase when using such information in dairy cattle studies, in which one or few breeds with limited diversity predominate. The objective of our study was to evaluate the accuracy of genomic prediction in a multi-breed Australian sheep population of relatively less related target individuals, when using information on imputed WGS genotypes.MethodsBetween 9626 and 26,657 animals with phenotypes were available for nine economically important sheep production traits and all had WGS imputed genotypes. About 30% of the data were used to discover predictive single nucleotide polymorphism (SNPs) based on a genome-wide association study (GWAS) and the remaining data were used for training and validation of genomic prediction. Prediction accuracy using selected variants from imputed sequence data was compared to that using a standard array of 50k SNP genotypes, thereby comparing genomic best linear prediction (GBLUP) and Bayesian methods (BayesR/BayesRC). Accuracy of genomic prediction was evaluated in two independent populations that were each lowly related to the training set, one being purebred Merino and the other crossbred Border Leicester x Merino sheep.ResultsA substantial improvement in prediction accuracy was observed when selected sequence variants were fitted alongside 50k genotypes as a separate variance component in GBLUP (2GBLUP) or in Bayesian analysis as a separate category of SNPs (BayesRC). From an average accuracy of 0.27 in both validation sets for the 50k array, the average absolute increase in accuracy across traits with 2GBLUP was 0.083 and 0.073 for purebred and crossbred animals, respectively, whereas with BayesRC it was 0.102 and 0.087. The average gain in accuracy was smaller when selected sequence variants were treated in the same category as 50k SNPs. Very little improvement over 50k prediction was observed when using all WGS variants.ConclusionsAccuracy of genomic prediction in diverse sheep populations increased substantially by using variants selected from whole-genome sequence data based on an independent multi-breed GWAS, when compared to genomic prediction using standard 50K genotypes.

Productive and Reproductive Performances of Indigenous Sheep in Ethiopia: A Review

Sheep in Ethiopia is among the major economically important livestock species in the country, playing a significant role to the livelihood of resource-poor farmers and pastoralists. A number of research works were done in the past which evaluate and improve the performance of indigenous sheep in Ethiopia. However, compiled information concerning the production and reproduction potential of indigenous sheep in the country is not available. In this paper, performance of major production and reproduction traits of indigenous sheep is reviewed and discussed. The information presented in this review indicated that, 16 to 126 g/d average daily gain, 7 - 18 kg hot carcass weight and dressing percentage of 34% to 49% (slaughter body weight basis) at 18 - 26 kg slaughter body weight have been recorded for Ethiopian sheep breeds fed various type of basal and supplement diets. These parameters showed variation within a breed and among breeds in various feeding trials and they increased as the level of supplement increases. However, despite sizeable information upon the response of sheep to various types of supplementary feeding, their full growth and other production potential of the majority of sheep breeds of the country are not well studied. Therefore, in future research work, emphasis should be given to explore the genetic potential of various production traits of sheep breeds of the country. Regarding the level of reproduction, 11 to 16 month age at first lambing (for most sheep breeds) and 7 to 10 month lambing intervals have been reported by various authors. The litter size result (1.01 to 1.7 lambs) showed that, there is high capability of Ethiopian sheep to give multiple births. The average pre-weaning mortality rate for most Ethiopian sheep breeds vary from 8% to 56%, which indicated that mortality is a major constraint that affects productivity of sheep in Ethiopia. Generally from the previous results it can be concluded that there is high variability within a breed and among Ethiopian sheep breeds in various production and reproduction traits. This implicates the presence of huge opportunity to improve these traits through improved management and selection.

Investigation on relationships of the FABP3 and SLC27A3 genes with milk production traits in sheep

Investigation on relationships of the FABP3 and SLC27A3 genes with milk production traits in sheep

Advances in genomic strategies to improve growth and meat production traits in sheep: An overview

Growth and meat production traits (body weight at birth, 3-months and 6-months, eye muscle area, fat thickness, pre-weaning and post-weaning gains, average daily weight gain, chest girth, height at withers and shin circumference) are reviewed to know the relationship with the loci which are controlled by specific genes that are associated with these traits. Quantitative trait loci (QTL) for different body and carcass weight traits are identified. Chromosomes 1, 2, 3, 4, 5, 6, 16, 18 and 20 are considered as candidate genomic regions for body weight and some major gene effects like transferrin gene on chromosome 1, Belgium Texel double muscling and myostatin (MSTN) gene on chromosome 2, growth effect around insulin-like growth factor 1 (IGF-1) on chromosome 3, calpastatin gene on chromosome 5, leptin gene on chromosome 4, Booroola fecundity gene on chromosome 6, growth hormone receptor (GHR) gene in chromosome 16, callipyge effect and carawell muscle hypertrophy on chromosome 18 and MHC complex on chromosome 20 have been identified. High-throughput genotyping and next-generation sequencing technologies are the advanced techniques for the creation of the high-density SNP array as a tool for the genomic analysis of domestic animals. Genome-wide association studies (GWAS) and genomic selection are the ultimate use of SNP array for the improvement of economically important traits. Hence, genome-wide sequencing is an advanced tool which may help in better selection of animal genetic resources. It may be used for applying molecular breeding strategies in genetic improvement programmes oflivestock.

Ovar-DRB1 haplotypes *2001 and *0301 are associated with sheep growth and ewe lifetime prolificacy

BackgroundThe major histocompatibility complex (MHC) is an organized cluster of tightly linked vertebrate genes with immunological and non-immunological functions. While the important MHC gene DRB1 has been examined in regard to many sheep infectious disease traits, only one study, based on microsatellite markers, has previously examined DRB1 and sheep production traits. Furthermore, to our knowledge no studies have examined DRB1 relationship with lifetime ewe prolificacy traits. Therefore, we analyzed association between the presence of DRB1 SNP haplotypes with internationally recognized standard names and production traits including growth and lifetime prolificacy in 370 Rambouillet, Columbia, and Polypay sheep. ResultsThe DRB1 *2001 haplotype was associated with increased weaning and mature weights, as well as average daily gain (Šidák P<0.05; corrected for the number of haplotypes tested). Interestingly, the *2001 haplotype also showed a trend toward association with increased total number of lifetime lambs born (Šidák P=0.084) and number of lambs born alive (Šidák P=0.084). In contrast, the DRB1 *0301 haplotype was associated with decreased mature weight (Šidák P=0.01). ConclusionsSince the *2001 haplotype was present in all three breeds, these results suggest there is at least one functional mutation in the region that influences growth and prolificacy traits that may be broadly present across several breeds. Furthermore, combined use of the similar *2001 and *0301 multi-marker haplotypes that nonetheless have opposing directions of production trait associations will enhance mutation discovery in this region. If undesirable alleles for underlying mutations can be identified, selective pressure against one or a small number of undesirable alleles may improve production with limited impact on MHC genetic diversity and infectious disease susceptibility.

Is it feasible to select humid sub-tropical Merino sheep for faecal egg counts?

Genetic parameter estimates for faecal egg counts (FEC), weaning and shearing weights and wool traits were evaluated in 720 Australian Merino lambs raised in Southern Brazil. Weaned lambs were naturally exposed to nematode larvae-contaminated pastures with the objective of recording individual gastrointestinal parasite infection responses. Phenotypic and genetic correlations among production traits such as birth, weaning and shearing weights and wool production traits (greasy and clean fleece weights, scouring yield, mean fibre diameter, and staple length) were estimated. Results showed a high variability for FEC counts among individuals, with a heritability estimate of 0.365±0.001, and low phenotypic and genetic correlations between FEC and all productive traits, except for a negative shearing live weight (rG=−0.305±0.002 and rP=−0.140±0.001). These results indicate that selection for low FEC would ensure genetic progress in reducing gastrointestinal parasite infection levels without limiting major sheep production traits for Merino sheep raised in a humid sub-tropical environment.

The expression of the SCD1 gene and its correlation with fattening and carcass traits in sheep

Abstract. Stearoyl-CoA desaturase 1 (SCD1) is a critical enzyme that catalyzes the synthesis of monounsaturated fatty acids and is involved in several signaling pathways related to lipid metabolism. The objective of the present study was to estimate the expression of the SCD1 gene in three different ovine tissues strongly associated with lipid homeostasis. The SCD1 gene expression measurement was performed on three tissues (liver, subcutaneous fat, perirenal fat) originated from 15 old-type Polish Merino sheep. The SCD1 transcript abundance was evaluated based on the two most stable endogenous controls (RPS2 – ribosomal protein S2; ATP5G2 – H(+)-transporting ATP synthase). The highest expression of the SCD1 gene was observed in ovine subcutaneous fat compared to perirenal fat and liver. Furthermore, the present research indicated the significant correlation between ovine SCD1 transcript abundance and several important production traits. The expression of the SCD1 gene in liver and perirenal fat highly positively correlated with the feed : gain ratio, test of daily gain and age of the animals at slaughter. Moreover, in both tissues, the SCD1mRNA level positively correlated with weight and content of perirenal fat and subcutaneous fat (R = 0.64, 0.8, 0.6, respectively) and negatively with assessment of external fat content with the use of the EUROP scale (R = −0.64). The SCD1 expression in subcutaneous fat also corresponds with back fat of blade chop and thickness of longissimus dorsi muscles evaluated using USG (ultrasonography) (R = −0.6 and 0.62, respectively). The significant correlation between SCD1 transcript abundance and fattening and slaughtering traits indicate the ability to improve important production traits in sheep via modification of expression of the SCD1 gene.

Identification of quantitative trait loci underlying milk traits in Spanish dairy sheep using linkage plus combined linkage disequilibrium and linkage analysis approaches

In this study, 2 procedures were used to analyze a data set from a whole-genome scan, one based on linkage analysis information and the other combing linkage disequilibrium and linkage analysis (LDLA), to determine the quantitative trait loci (QTL) influencing milk production traits in sheep. A total of 1,696 animals from 16 half-sib families were genotyped using the OvineSNP50 BeadChip (Illumina Inc., San Diego, CA) and analysis was performed using a daughter design. Moreover, the same data set has been previously investigated through a genome-wide association (GWA) analysis and a comparison of results from the 3 methods has been possible. The linkage analysis and LDLA methodologies yielded different results, although some significantly associated regions were common to both procedures. The linkage analysis detected 3 overlapping genome-wise significant QTL on sheep chromosome (OAR) 2 influencing milk yield, protein yield, and fat yield, whereas 34 genome-wise significant QTL regions were detected using the LDLA approach. The most significant QTL for protein and fat percentages was detected on OAR3, which was reported in a previous GWA analysis. Both the linkage analysis and LDLA identified many other chromosome-wise significant associations across different sheep autosomes. Additional analyses were performed on OAR2 and OAR3 to determine the possible causality of the most significant polymorphisms identified for these genetic effects by the previously reported GWA analysis. For OAR3, the analyses demonstrated additional genetic proof of the causality previously suggested by our group for a single nucleotide polymorphism located in the α-lactalbumin gene (LALBA). In summary, although the results shown here suggest that in commercial dairy populations, the LDLA method exhibits a higher efficiency to map QTL than the simple linkage analysis or linkage disequilibrium methods, we believe that comparing the 3 analysis methods is the best approach to obtain a global picture of all identifiable QTL segregating in the population at both family-based and population-based levels.