Sheep Breeds Research Articles

Mixed grazing of cattle with sheep and goats as a solution for livestock farmers in Greece and other countries around the Mediterranean Sea: a review

The management of common pastures is often a matter of conflict between cattle farmers and small ruminants (goats and sheep), especially in areas with small pastures and low capacity. This conflict is reflected in a relevant opinion survey in Evrytania (Central Greece) where cattle farmers consider that cattle can graze together with goats and/or sheep while goat and sheep farmers consider that cattle should be restricted to separate pastures. However, international experience as reflected in publications, mainly from the USA, shows that the co-grazing of cattle with goats and/or sheep, under certain conditions, can yield multiple benefits which have not been particularly highlighted in Greece. The aim of this paper is to investigate the potential of co-grazing of cattle with small ruminants and to list the benefits of this practice.

Efficacy of Commonly Used Anthelmintics Against Naturally Occurring Gastrointestinal Nematodes in Goats

Efficacy of four commonly used anthelmintics have been evaluated against naturally occurring gastrointestinal nematodes in goats following the method of faecal egg count reduction test (FECRT) in the present study. Fifty goats in the age group of 1 to 2 years old and of either sex, having infection with strongyle group of nematodes were selected in the sheep and goat farm under project ‘Biotech Kisan Hub”, West Bengal University of Animal and Fishery sciences and the goats were equally divided into five groups; group I (infected control), group II (albendazole treated), group III (fenbendazole treated), group IV (ivermectin treated) and group V (levamisole treated). Faecal egg count (FEC) in terms of eggs per gram of faeces (EPG) were estimated in all the experimental goats (n = 50) on 0-day post treatment (0 DPT) and again on 10 DPT. Efficacy of albendazole, fenbendazole, ivermectin and levamisole were 78.15%, 80.24%, 86.38% and 95.46%, respectively. Comparatively less efficacy of albendazole and fenbendazole indicated the emergence of anthelmintic resistance and lower efficacy of ivermectin might be due selection of resistant worms. Efficacy of levamisole was comparatively higher and it can be used strategically to control GI helminth parasites of goats in that farm.

Analyzing the expression of the transcriptome in adipose tissue of fat- and thin-tailed sheep

Significant efforts have been made to understand how fat deposition in sheep tail is regulated in genetic, transcriptomic, physiologic, biochemical, and metabolic levels in order to elucidate the complex mechanisms underlying the energy storage, lipid metabolism in adipose tissue, adaptability to harsh environments, and evolutionary domestication. Through RNA-seq data analysis, we are able to compare the gene expression of fat-tailed sheep versus thin-tailed sheep breeds in an acceptable resolution at transcriptome level. The purpose of this study was to compare the transcriptomes of Ghezel (fat-tailed) and Zel (thin-tailed) sheep. Total RNA from subcutaneous and tail tissue samples from healthy lambs was sequenced (150b PE) to identify differentially expressed genes (DEGs) between the two mentioned tissues and between the Ghezel and Zel sheep breeds. Further downstream pathway and network analyses were conducted afterwards. The results uncovered the association of the most important DEGs such as CAV1, ALB, and SOCS3 with cellular signaling pathways of lipids metabolism. It seems that the SOCS3 gene plays an important role in the differential deposition of lipid in the tails of two phenotypically different sheep breeds. Although the detail of gene expression in the tail and subcutaneous tissues of two morphologically different breeds was decoded here, to fully understand how differential expression of the SOCS3 gene affects the fat synthesis, further studies are needed.

Insight into the differences in meat quality among three breeds of sheep on the Qinghai-Tibetan plateau from the perspective of metabolomics and rumen microbiota

Mutton is one of the most popular meats among the general public due to its high nutritional value. This study evaluated the differences in meat quality among Chaka (CK), Black Tibetan (BT) and Oula (OL) sheep and investigated the metabolic mechanisms affecting meat quality using targeted and untargeted metabolomics and 16S rRNA. The results showed that the meat quality of CK sheep was superior to that of BT and OL sheep in terms of meat color, muscle fiber characteristics and nutritional quality. Pseudobutyrivibrio, Alloprevotella, Methanobrevibacter, unidentified_Christensenellaceae, and unidentified_Bacteroidales were key microbes involved in regulating meat color, muscle fiber characteristics, amino acid and fatty acid content. Protein digestion/absorption, pentose phosphate metabolism, carbon metabolism, and glyoxylate and dicarboxylate metabolism were important metabolic pathways involved in meat quality regulation. Our study is important for the development of sheep breeding strategy and sheep meat industry in Qinghai-Tibetan Plateau.

Genetic parameters for growth and reproductive traits in Santa Inês sheep

Although Santa Inês sheep demonstrate good adaptation to tropical environments, there is a need for effective breeding programs focused on growth and reproductive traits to harness the breed's full developmental potential. Thus, this study aimed to estimate (co)variance components and genetic parameters for weight at birth (WB), weight at 60 days (W60), age at first lambing (AFL), first lambing interval (FLI), and average lambing interval (AFI) in Santa Inês sheep. The data were obtained from the Sergipe Goat and Sheep Breeders' Association (ASCCO). (Co)variance components and genetic parameters were estimated by Bayesian analysis based on a bitrait model with Gibbs sampling using Multiple-Trait Gibbs Sampler for Animal Models (MTGSAM) software. Heritability estimates (h2) for WB, W60, AFL, ALI, and FLI were 0.11, 0.18, 0.028, 0.25, and 0.30, respectively. Positive correlations were observed between WB and W60, AFL and ALI, and AFL and FLI (0.31, 0.17, and 0.18, respectively). By contrast, negative correlations were obtained for WB and AFL (−0.55), WB and AFL (−0.42), WB and FLI (−0.39), W60 and ALI (−0.26), and W60 and FLI (−0.37), with magnitudes ranging from low to moderate. Correlation values for ALI and FLI and W60 and AFL were positive and strong (0.97 and 0.98, respectively). These results indicate that the studied traits can be used for indirect selection. Furthermore, the findings underscore the importance of determining genetic parameters when formulating strategies for the genetic improvement of Santa Inês sheep.

Developmental three-dimensional examination of the pelvic cavity of Hamdani crossbred sheep fetuses (Ovis aries) in the last two periods of gestation.

Türkiye is a country in the world ranking in terms of sheep breeding. Hamdani crossbred sheep breed is one of the sheep breeds that can adapt to the difficult conditions in our country. In addition, the sentence may be corrected as 'Especially in the southeastern part of the Türkiye, crossbreeding is preferred by breeders to increase the yield characteristics of sheep'. In our study, it was aimed to perform a pelvimetric analysis of Hamdani crossbred sheep fetuses in the second and third trimesters by three-dimensional modelling method. For this purpose, a total of 40 second-trimester (10 females, 10 males) and third-trimester (10 females, 10 males) fetuses were used. The pelvises of the fetuses were imaged with CT and 3D models were created. Sixteen pelvimetric measurements were performed from the models. The results obtained were evaluated statistically. The study found statistically significant differences between male and female fetuses in terms of vertical diameter (VD) and foramen obturatum width (FOW) measurement parameters in the second trimester. In the third trimester, there were statistically significant differences between genders in acetabulum (AC) (p < 0.01), medial ischial tuberosities (MIT), and ischiatic arch (IA) (p < 0.05) parameters. As a result of the correlation analysis, it was determined that the pelvis length (PL) measurement parameter was positively correlated with different parameters in varying degrees in both periods, while the IA parameter did not show significant correlations with the other parameter in the last two periods of pregnancy. In conclusion, the data obtained will be useful in pelvimetric evaluations of human and animal fetuses, anatomy education, zooarchaeology and taxonomy studies.

Carbon Footprint of an Extensively Raised, Low-Productivity Sheep Population

Extensive traditional livestock systems currently face various threats, leading to their disappearance. An example of these extensive livestock farming systems is the production of the Lojeña sheep breed in the Sierra de Loja (Granada, Spain), with a census of 24,511 ewes in 2021. The aim of this work is to calculate the carbon footprint (CF) of this local breed in this region. This study is based on data collected from 27 Lojeña sheep farms producing weaned lambs (≤14 kg, 25 farms), fattened lambs (≈25 kg, 7 farms), culled animals (24 farms) and greasy wool (27 farms). Most of these farms (78%) were organically (ORG) certified and seven were conventionally (CONV) managed. The analysed farms represent 93% of the total number of farms producing Lojeña sheep in the Sierra de Loja. The CF was calculated with a “cradle to farm gate” approach. The average C footprints were 27.5 ± 6.8 kg CO2eq kgLW−1 for weaned lambs, 21.8 ± 8.5 kg CO2eq kgLW−1 for fattened lambs, 4.1 ± 2.6 kg CO2eq kgLW−1 for culled animals and 2.2 ± 0.6 kg CO2eq kg−1 for greasy wool, with a not statistically different average CF in ORG than in CONV farms. Enteric fermentation represents the main source of emissions (&gt;60%) in all the products, and external feeding (including transport, and emissions from producing the feed) represents the second one (&gt;10%). There was an inverse relationship between CF and productivity (lambs sold ewe−1 year−1), leading to lower footprints on those farms with the higher productivity. A direct relationship between CF and stocking rate (livestock units ha−1) has been identified.

BREEDING ACHIEVEMENTS OF UKRAINE (PAST, PRESENT): BREEDS, TYPES AND LINES OF AGRICULTURAL ANIMALS

The purpose of the study was to establish chronologically breeding achievements in livestock breeding of Ukraine with the help of the relevant Register. To analyze the dynamics of the number of breeding animals, the State Register of Breeding Subjects in Livestock Breeding for the period 2002 ... 2022 was used. The genealogical structure of the six studied breeds of dairy cattle includes 10 interbreed and 11 local types, 47 local and 38 genealogical lines and about 244 families. Beef cattle are represented by four approved breeds, 4 interbreed and 2 local types, 32 lines and 172 families. The pedigree pig breeding of Ukraine includes seven domestic breeds with three interbreed types, 11 local types, 95 lines and 159 families. In the fields of sheep breeding and horse breeding, five and two breeds were created, respectively, and their genealogical structure was formed from 11 interbreed types and 28 families in sheep breeding and 15 lineages and related groups and 25 families in horse breeding. One breed and two crosses (10 lines) of laying hens, one cross (two lines and eight microlines) of turkeys and four breed groups of ducks represent poultry breeding.

The Use of Machine Learning to Predict Prevalence of Subclinical Mastitis in Dairy Sheep Farms.

The objective of the study was to develop a computational model with which predictions regarding the level of prevalence of mastitis in dairy sheep farms could be performed. Data for the construction of the model were obtained from a large Greece-wide field study with 111 farms. Unsupervised learning methodology was applied for clustering data into two clusters based on 18 variables (17 independent variables related to health management practices applied in farms, climatological data at the locations of the farms, and the level of prevalence of subclinical mastitis as the target value). The K-means tool showed the highest significance for the classification of farms into two clusters for the construction of the computational model: median (interquartile range) prevalence of subclinical mastitis among farms was 20.0% (interquartile range: 15.8%) and 30.0% (16.0%) (p = 0.002). Supervised learning tools were subsequently used to predict the level of prevalence of the infection: decision trees, k-NN, neural networks, and Support vector machines. For each of these, combinations of hyperparameters were employed; 83 models were produced, and 4150 assessments were made in total. A computational model obtained by means of Support vector machines (kernel: 'linear', regularization parameter C = 3) was selected. Thereafter, the model was assessed through the results of the prevalence of subclinical mastitis in 373 records from sheep flocks unrelated to the ones employed for the selection of the model; the model was used for evaluation of the correct classification of the data in each of 373 sets, each of which included a test (prediction) subset with one record that referred to the farm under assessment. The median prevalence of the infection in farms classified by the model in each of the two categories was 10.4% (5.5%) and 36.3% (9.7%) (p < 0.0001). The overall accuracy of the model for the results presented by the K-means tool was 94.1%; for the estimation of the level of prevalence (<25.0%/≥25.0%) in the farms, it was 96.3%. The findings of this study indicate that machine learning algorithms can be usefully employed in predicting the level of subclinical mastitis in dairy sheep farms. This can facilitate setting up appropriate health management measures for interventions in the farms.

Assessment of genetic diversity and population structure of U.S. Polypay sheep from breed origins to future genomic selection.

Knowledge of past and present genetic diversity within a breed is critical for the design and optimization of breeding programs as well as the development of strategies for the conservation of genetic resources. The Polypay sheep breed was developed at the U.S. Sheep Experiment Station (USSES) in 1968 with the goal of improving productivity in Western U.S. range flocks. It has since flourished in the more intensively managed production systems throughout the U.S. The genetic diversity of the breed has yet to be documented. Therefore, the primary objective of this study was to perform a comprehensive evaluation of the genetic diversity and population structure of U.S. Polypay sheep using both pedigree- and genomic-based methods. Pedigree data from 193 Polypay flocks participating in the National Sheep Improvement Program (NSIP) were combined with pedigree records from USSES (n = 162,997), tracing back to the breed's origin. A subset of these pedigreed sheep from 32 flocks born from 2011 to 2023 were genotyped with the GGP Ovine 50K BeadChip containing 51,867 single nucleotide polymorphisms (SNPs). Four subgroups were used for the pedigree-based analyses: 1) the current generation of animals born in 2020-2022 (n = 20,701), 2) the current generation with a minimum of four generations of known ancestors (n = 12,685), 3) only genotyped animals (n = 1,856), and 4) the sires of the current generation (n = 509). Pedigree-based inbreeding for the full population was 2.2%, with a rate of inbreeding of 0.22% per generation. Pedigree-based inbreeding, Wright's inbreeding, and genomic inbreeding based on runs of homozygosity were 2.9%, 1.3%, and 5.1%, respectively, for the genotyped population. The effective population size ranged from 41 to 249 for the pedigree-based methods and 118 for the genomic-based estimate. Expected and observed heterozygosity levels were 0.409 and 0.403, respectively. Population substructure was evident based on the fixation index (FST), principal component analysis, and model-based population structure. These analyses provided evidence of differentiation from the foundation flock (USSES). Overall, the Polypay breed exhibited substantial genetic diversity and the presence of a population substructure that provides a basis for the implementation of genomic selection in the breed.

Variation in the Exon 3-4 Region of Ovine KRT85 and Its Effect on Wool Traits.

α-keratins are structural proteins in the cortex of wool fibres and assemble in an organized fashion into keratin intermediate filaments. Variation in these keratin proteins affects the structure and characteristics of wool fibre, making keratin genes ideal candidates for the development of gene markers that describe variations in wool traits. A region of KRT85 spanning exon 3-4 (including the entire exon 3, intron 3, exon 4 and part of intron 4) was investigated. Two banding patterns defining two variant sequences (A and B) were observed in this region, and these were characterised by the presence of two single nucleotide polymorphisms. The effect of this variation in the exon 3-4 region of KRT85 on wool traits was investigated in 463 Merino × Southdown-cross lambs. The frequencies of these two variants in these sheep were 55.6% and 44.4%, respectively. Three different genotypes were observed with frequencies of 32.6%, 46.1% and 21.3% for AA, AB and BB, respectively. The presence of A was associated with an increase in greasy fleece weight and clean fleece weight, while the presence of B was associated with an increased wool prickle factor. These findings should be replicated in a broader range of sheep breeds to determine whether the associations are robust and to clarify whether the observed effects are attributable to breed differences or to gene effects themselves.

De- and repeasantisation through wolves: a political ecology of predator-friendly farming

While wolves are often described as 'ecological engineers', this article reframes the image of this predator as a socioecological engineer. Adopting a more-than-human political ecology perspective, I highlight the imbrication of wolf agency with the political economy of farming in co-shaping processes of agrarian change in Tuscany, Italy. A multispecies ethnography elucidates how wolves are simultaneously contributing to and undermining a modernization of sheep husbandry practices in the region. This entanglement of wolf agency in processes of de- and re-peasantization is politically relevant, affecting human-wolf relations and local levels of conflict. Through their return, wolves are necessitating shifts in farming practices and affecting the topology of agricultural landscapes, favoring either an intensification of husbandry regimes (i.e., more sheep raised indoors) or a greater competitiveness of family-led free-ranging farms with a high availability of family labor. Emphasizing this aspect is important to politicize current discussions surrounding coexistence, and supports the rise of practices that are considered to be most socially, culturally, and ecologically valuable. A focus on wolf agency in this case entails 'thinking with' wolves in co-designing alternative (co)existences, providing a more nuanced understanding of socioecological change and human-wolf relations. This article informs critical scholarship on the value of moving beyond dualist lenses while still maintaining a focus on structural processes. These are an important though not unidirectional force of change. Reframing wolves as socioecological engineers calls for further research exploring such entanglements of human and non-human agencies in the coproduction of agrarian change and human-wildlife relations.

Bibliometric Analysis and Science Mapping on RNA-seq and Gene Expression in Sheep

This study aimed to determine the development of research articles on ‘RNA-sequencing and gene expres-sion’ in sheep between 2011-2023 in the Web of Science (WoS) database by scientific mapping method. In this regard, 205 articles were examined in the first search using the relevant keywords, and 124 articles suitable for analysis. They were analysed with the Shiny web application of the Bibliometrix R package, and VOSviewer. The results determined that the country with the most publications in the relevant field was China, the related institution with the most studies was “The University of Edinburgh”, and the journal with the most publications was “PLoS One”. According to the key-word analysis, the trend topics started from studies on granulosa cells and showed into research areas such as im-mune response, growth, pathway and meat quality. In the abstract analysis, the word ‘transcriptome’ and words such as mammary gland, muscle, fertility, Peripheral Blood Mononuclear Cells (PBMCs), lactation, fat storage were found together, while the words forming the parasitic agents, drug resistance, miRNA studies were clustered in different groups. The scarcity of the articles obtained in the analysed period reveals the openness of the study area. It can be suggested that the researchers who will plan to work on this subject can plan studies on the identification of variants belonging to different sheep breeds, resistance to antiparasitic drugs used in sheep, meat yield, disease resistance, reproductive tissues and organs, as well as designing all these studies as study subjects based on climate change and global warming factor.

Whole genome sequencing reveals that five genes are related to BW trait in sheep

BW is an important economic trait in sheep that influences growth and development. Currently, most studies have used a single approach to screen genes associated with BW traits in sheep. To address this limitation, we conducted a genome-wide association study (GWAS) covering four different BW periods: birth, weaning, 6 months, and 12 months. Five new candidate genes: MAP3K1, ANKRD55, ABCB1, MEF2C and TRNAW-CCA-87 were screened using a combination of GWAS and quantitative trait loci analysis in sheep. Additionally, five genes were subjected to Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. These genes were primarily enriched in pathways related to growth hormone and energy metabolism. The results demonstrated that the above genes potentially influenced the growth and development of sheep. The five new candidate genes are closely related to the BW trait in sheep, which will be valuable for understanding the genetic mechanisms underlying BW traits and for guiding sheep breeding.

Vibration characteristics analysis and structural optimization of bio-organic fertilizer mixer based on finite element method

Abstract In order to solve the waste produced by grape planting and cattle and sheep breeding in the Turpan area, this paper puts forward an organic liquid fertilizer mixer, and analyzes the vibration characteristics of the main structure-mixing barrel and auger. The finite element model of the mixer structure is established by Ansys, and the modal analysis is carried out in combination with the actual application. The analysis structure shows that the minimum natural frequency of the mixer barrel is 51.993 Hz, the minimum natural frequency of the auger is 12.601 Hz, in which the natural frequency of the auger is less than its working frequency of 48.5 Hz, and there is resonance risk. To improve this problem, the structure of the mixing auger is optimized, the length of the auger is reduced, and the pipe thickness and diameter are increased. The improved modal analysis shows that the minimum natural frequency of the auger is 50.371 Hz, which avoids the working frequency and will not cause resonance.

Q fever endocarditis of the tricuspid valve transmitted in an urban setting with no livestock exposure: Case report

BackgroundCoxiella burnetii is a bacterium with extreme tenacity and contagiousness that is mainly transmitted by inhalation of contaminated aerosols. Nevertheless, a transmission by ticks is under discussion. We report a case of Q fever in an urban environment and far away from sheep breeding that caused a rare right-sided endocarditis.Case presentationA 55-year-old man who was in good health before the event developed a C. burnetii -endocarditis of the tricuspid valve. He had no contact with sheep and no recent travel in a rural or even endemic area. The infection originated in a strictly urban environment, and the patient’s occupation as a cemetery gardener in Berlin, coupled with the close temporal and local exposure to wild boar, made a transmission by these animals a plausible hypothesis. The infection was confirmed by the German Reference Laboratory, and the patient recovered completely after treatment with doxycycline and hydrochlorquine.ConclusionsThe specialities of this case report are the right-sided endocarditis and the transmission of C. burnetii in a metropolitan area without sheep contact. We think that this case should serve to increase awareness of the potential for Q fever infection even in non-rural areas.

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.

Molecular signatures of Haemonchus contortus infection in sheep: A comparative serum proteomic study on susceptible and resistant sheep breeds

Due to the negative impact of Haemonchus contortus in the tropics and subtropics, the detection of serum protein profiles that occur in infected sheep is of high relevance for targeted selective treatment strategies (TST). Herein, we integrated proteomics with phenotypic traits to elucidate physiological mechanisms associated to H. contortus infection in susceptible (Dorper – D) and resistant (Santa Inês – S) sheep breeds. Naïve female lambs were infected with H. contortus third-stage larvae on day zero (D0), and samples were collected weekly, for 28 days. Feces were used for individual fecal egg counts (FEC) blood for packed cell volume (PCV) and serum for specific antibody quantification through ELISA. Sera was collected on D0 (-) and D21 (+), and analyzed using a LC-MS/MS based proteomics approach. FEC, PCV, and anti-H. contortus antibody levels confirmed the absence of infection on D0. On D28 there was a significant difference between the two breeds for logFEC means (D = 3774 and S = 3141, p=0.033) and PCV means (D = 16.3 % and S = 24.3 %, p=0.038). From a total of 754 proteins identified, 68 differentially abundant proteins (DAPs) were noted. Phosphopyruvate hydratase (ENO3) was a DAP in all comparisons, while S+ vs D+ and S- vs D- shared the highest number of DAPs (8). Each of the four experimental groups clustered separately in a principal component analysis (PCA) of protein profile. Among the DAPs, proteins associated with the innate and adaptive immune system were detected when comparing S- vs D- and S+ vs D+. In D-, some proteins were linked to stress response to handling, sampling and heat. Focusing on the consequences of infection in each breed, in the D+ vs D- comparison, upregulated proteins were associated with inflammation control and immune response, where downregulated proteins pointed to a negative impact of infection on tissue anabolism, compromising muscle growth and fat deposition. In the S+ vs S- comparison, upregulated proteins were related to immune response, while the downregulated proteins were possibly linked to muscular development and growth, impaired by infection. Collectively, it can be concluded that ENO3 regulation emerges as a potential factor underlying the differential immune response observed between Santa Inês and Dorper sheep infected with H. contortus. In turn, detected acute phase proteins (APPs) reinforce their relation with infection, inflammation and stress conditions, whereas THEMIS-like may contribute to the immune system in Dorper. GSDMD, Guanylate-binding protein and ACAN warrant further investigation as possible biomarkers for TST strategy development.

Genome-wide association studies of body size traits in Tibetan sheep

BackgroundElucidating the genetic variation underlying phenotypic diversity will facilitate improving production performance in livestock species. The Tibetan sheep breed in China holds significant historical importance, serving as a fundamental pillar of Qinghai’s animal husbandry sector. The Plateau-type Tibetan sheep, comprising 90% of the province’s population, are characterized by their tall stature and serve as the primary breed among Tibetan sheep. In contrast, Zhashijia sheep exhibit larger size and superior meat quality. These two species provide an excellent model for elucidating the genetic basis of body size variation. Therefore, this study aims to conduct a comprehensive genome-wide association study on these two Tibetan sheep breeds to identify single nucleotide polymorphism loci and regulatory genes that influence body size traits in Tibetan sheep.ResultIn this study, the phenotypic traits of body weight, body length, body height, chest circumference, chest depth, chest width, waist angle width, and pipe circumference were evaluated in two Tibetan sheep breeds: Plateau-type sheep and Zhashijia Tibetan sheep. Whole genome sequencing generated 48,215,130 high-quality SNPs for genome-wide association study. Four methods were applied and identified 623 SNPs significantly associated with body size traits. The significantly associated single nucleotide polymorphisms identified in this study are located near or within 111 candidate genes. These genes exhibit enrichment in the cAMP and Rap1 signaling pathways, significantly affecting animal growth, and body size. Specifically, the following genes were associated: ASAP1, CDK6, FRYL, NAV2, PTPRM, GPC6, PTPRG, KANK1, NTRK2 and ADCY8.ConclusionBy genome-wide association study, we identified 16 SNPs and 10 candidate genes associated with body size traits in Tibetan sheep, which hold potential for application in genomic selection breeding programs in sheep. Identifying these candidate genes will establish a solid foundation for applying molecular marker-assisted selection in sheep breeding and improve our understanding of body size control in farmed animals.

Genetic diversity of United States Rambouillet, Katahdin and Dorper sheep

BackgroundManaging genetic diversity is critically important for maintaining species fitness. Excessive homozygosity caused by the loss of genetic diversity can have detrimental effects on the reproduction and production performance of a breed. Analysis of genetic diversity can facilitate the identification of signatures of selection which may contribute to the specific characteristics regarding the health, production and physical appearance of a breed or population. In this study, breeds with well-characterized traits such as fine wool production (Rambouillet, N = 745), parasite resistance (Katahdin, N = 581) and environmental hardiness (Dorper, N = 265) were evaluated for inbreeding, effective population size (Ne), runs of homozygosity (ROH) and Wright’s fixation index (FST) outlier approach to identify differential signatures of selection at 36,113 autosomal single nucleotide polymorphisms (SNPs).ResultsKatahdin sheep had the largest current Ne at the most recent generation estimated with both the GONe and NeEstimator software. The most highly conserved ROH Island was identified in Rambouillet with a signature of selection on chromosome 6 containing 202 SNPs called in an ROH in 50 to 94% of the individuals. This region contained the DCAF16, LCORL and NCAPG genes that have been previously reported to be under selection and have biological roles related to milk production and growth traits. The outlier regions identified through the FST comparisons of Katahdin with Rambouillet and Dorper contained genes with known roles in milk production and mastitis resistance or susceptibility, and the FST comparisons of Rambouillet with Katahdin and Dorper identified genes related to wool growth, suggesting these traits have been under natural or artificial selection pressure in these populations. Genes involved in the cytokine-cytokine receptor interaction pathways were identified in all FST breed comparisons, which indicates the presence of allelic diversity between these breeds in genomic regions controlling cytokine signaling mechanisms.ConclusionsIn this paper, we describe signatures of selection within diverse and economically important U.S. sheep breeds. The genes contained within these signatures are proposed for further study to understand their relevance to biological traits and improve understanding of breed diversity.