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The potential of using long in vitro culture (LIVC) of cumulus-oocyte complexes (COCs) from early antral follicles (EAFs) as an assisted reproductive technology in cattle has shown promising results. This study explored the feasibility of applying this technology to sheep as seasonal breeding animals. Ovaries from sheep were collected during both the breeding and non-breeding seasons. COCs were isolated from EAFs (350–450 μm) and cultured in TCM199 medium supplemented with 0.15 μg/mL Zn sulfate, 10−4IU/mL FSH, 10 ng/mL estradiol, 50 ng/mL testosterone, 50 ng/mL progesterone, and 5 μM Cilostamide. After five days of LIVC, the COCs were submitted to an in vitro maturation procedure. The results indicate successful in vitro development of COCs, evidenced by a significant increase in oocyte diameter (p < 0.000) and the preservation of gap junction communication between oocyte and cumulus cells. The gradual uncoupling was accompanied by a progressive chromatin transition from the non-surrounded nucleolus (NSN) to the surrounded nucleolus (SN) (p < 0.000), coupled with a gradual decrease in global transcriptional activity and an increase in oocyte meiotic competence (p < 0.000). Maintenance of oocyte-cumulus investment architecture, viability, and metaphase II capability was significantly higher in COCs collected during the breeding season (p < 0.000), suggesting higher quality than those obtained during the non-breeding season. In conclusion, our study confirms LIVC feasibility in sheep, emphasizing increased effectiveness during the breeding season in isolating higher-quality COCs from EAFs. These findings can influence improving the LIVC system in mammals with seasonal reproduction. • LIVC protocol promotes efficient oocyte growth from sheep EAFs in the breeding season. • LIVC supports chromatin transition, reduces transcriptional activity, and enhances meiotic competence. • Cultured COCs showed higher viability, morphological integrity, and open gap junctions during the breeding season. [ABSTRACT FROM AUTHOR]

Genomic selection is widely implemented in livestock breeding programmes across species. Its potential is also evident for sheep breeding; however, it has several limitations, particularly because of the high genetic diversity across and within sheep breeds. In Germany, the predominant sheep breed is the Merino sheep. Until now, there has been no use of genomic selection in the German Merino sheep breeding programme. In this simulation study, different genomic selection strategies were compared with a reference scenario with a breeding value estimation based on pedigree BLUP. A simplified version of the German Merino sheep breeding programme, including a health and a production trait in the breeding goal, was simulated via the R package Modular Breeding Program Simulator (MoBPS). Real genotype data were used to create a population specific simulation. The reference scenario was compared with several alternative scenarios in which selection was based on single‐step GBLUP (ssGBLUP) breeding value estimation with varying genotyping strategies. In addition to scenarios in which all male and all male plus all female lambs were genotyped, scenarios with a preselection of lambs, that is only a certain proportion (top 25%, top 50%) genotyped, were simulated. The results revealed that genetic gain increased with increasing numbers of available genotypes. However, marginal gains decreased with increasing numbers of genotypes. Compared with the reference scenario, genotyping the top 25% of male lambs increased the genetic gain for the breeding ram population by 13% for both traits whereas genotyping the top 50% of male lambs or all male lambs led to increases of 18% (17%) or 26% (21%) for the health (production) trait, respectively. The potential of genotyping females in addition to male lambs was less evident on the male side with no significant differences between the scenarios with different proportions of genotyped females. The results have shown that genomic selection can be a valuable tool to increase genetic gain in the German Merino sheep population and that the genotyping of a certain proportion of animals might lead to substantial improvement over pedigree‐based breeding value estimation. Nevertheless, further studies, especially economic evaluations, are needed before practical implementation. [ABSTRACT FROM AUTHOR]

Background: The microbiota and metabolites in the gastrointestinal tracts of female animals at different reproductive periods are very important to the growth, development, and health of themselves and their offspring. However, the changes in the gastrointestinal microbiota and metabolites throughout reproductive period of different sheep breeds and their effects on the growth and development of offspring lambs are still unclear. Hence, this study presents an assessment of the reproductive hormone levels, immune levels, rumen microbiota, and metabolites in Hu sheep and Suffolk ewes at different reproductive periods and their effects on the growth and development of offspring lambs. Results: Hu sheep and Suffolk during non-pregnancy, pregnancy, and lactation were used as the research objects to determine reproductive and immune indexes of ewes at different periods, analyze rumen microbiome and metabolome, and track the growth performance and development of offspring lambs. The results showed that the reproductive hormone and immune levels of Hu sheep and Suffolk underwent adaptive changes across different reproductive periods. Compared with non-pregnancy, the microbial energy metabolism and lipid metabolism function decreased during Hu sheep pregnancy, and energy metabolism function decreased during lactation. In Suffolk, energy metabolism, glycan biosynthesis, and metabolism function were enhanced during pregnancy, and the metabolism of cofactors and vitamins was enhanced during lactation. Prevotella increased in Suffolk during pregnancy and lactation (P < 0.05) and was positively correlated with the birth weight and body size of the lambs (P < 0.05). Moreover, the abundances of Butyrivibrio and Rikenellaceae_RC9_gut_group during pregnancy were positively correlated with the intestinal immunity of the offspring lambs (P < 0.05), thereby regulating the intestinal immunity level of the lambs. Metabolomic analysis revealed that the protein digestion, absorption, and amino acid metabolism of Hu sheep were enhanced during pregnancy, which provided amino acids for the growth and development of pregnant ewes and fetuses and was significantly correlated with the birth weight, body size, and intestinal immunity of lambs (P < 0.05). Simultaneously, there was an increase in acetate and propionate during the pregnancy and lactation period of both Hu sheep and Suffolk, providing energy for ewes during reproductive period. Moreover, the microbiota during the lactation period was significantly correlated with the milk quality and lambs daily gain (P < 0.05). Conclusions: This study revealed the characteristic succession changes in the rumen microbiota and its metabolites at different reproductive periods in sheep breeds and their regulation of reproductive hormone and immune levels and identified their potential effects on the growth and development of offspring lambs. The findings provide valuable insights into the health and feeding management of different sheep breeds during the reproductive stage. Cnu7uEJBESQuA-vs1kGzfa Video Abstract [ABSTRACT FROM AUTHOR]

High-density genomic data analyzed by accurate statistical methods are of potential to enlighten past breeding practices such as selection by unraveling fixed regions. In this study, four native Turkish sheep breeds (80 samples) were genotyped via 296.097 single nucleotide polymorphisms (SNPs) detected by double-digest restriction site-associated DNA (ddRADseq) library preparation combined with the Illumina HiSeq X Ten instrument in order to identify genes under selection pressure. A total of 32, 136, 133, and 119 protein-coding genes were detected under selection pressure by runs of homozygosity (ROH), integrated haplotype score (iHS), the ratio of extended haplotype homozygosity (Rsb), and fixation index (FST) approaches, respectively. Of these, a total of 129 genes were identified by at least two statistical models which overlapped with a total of 52 quantitative trait loci (QTL)-associated SNPs, known to be related to fiber diameter, milk content, body weight, carcass traits, some blood parameters, and entropion. A total of six genes under selection pressure were validated by three statistical approaches five of which are of potential to be integrated into animal breeding since they were associated with wool fiber diameter (ZNF208B), behaviors related to neurocognitive development (CBX1 and NFE2L1), adaptation to high-altitude (SDK1), and anxiety causing internal stress (GSG1L). The sixth gene (COPZ1) turned out to play an important role in coping with different types of cancer in mammals. In particular, ROH analysis uncovered significant findings that the Güney Karaman (GKR) had experienced different selection practices than the Akkaraman (AKR) breed. Moreover, some genes specifically under selection in the GKR breed turned out to be associated with olfaction (OR6K6, OR6N1, OR6N2, and OR4C16), survival during the gestation period (PRR15L), and heat stress (CDK5RAP9). The results of this study imply that GKR may become genetically different from the AKR breed at the genome level due to most probably experiencing different adaptation processes occurring in raised climatic conditions. These differences should be conserved to face future challenges, while other native Turkish sheep breeds could be monitored via genome-wide high-density SNP data to obtain deeper knowledge about the effects of natural selection. [ABSTRACT FROM AUTHOR]

Background: Accurate breed identification is essential for the conservation and sustainable use of indigenous farm animal genetic resources. In this study, we evaluated the phylogenetic relationships and genomic breed compositions of 13 sheep breeds using SNP and InDel data from whole genome sequencing. The breeds included 11 Chinese indigenous and 2 foreign commercial breeds. We compared different strategies for breed identification with respect to different marker types, i.e. SNPs, InDels, and a combination of SNPs and InDels (named SIs), different breed-informative marker detection methods, and different machine learning classification methods. Results: Using WGS-based SNPs and InDels, we revealed the phylogenetic relationships between 11 Chinese indigenous and two foreign sheep breeds and quantified their purities through estimated genomic breed compositions. We found that the optimal strategy for identifying these breeds was the combination of DFI_union for breed-informative marker detection, which integrated the methods of Delta, Pairwise Wright's FST, and Informativeness for Assignment (namely DFI) by merging the breed-informative markers derived from the three methods, and KSR for breed assignment, which integrated the methods of K-Nearest Neighbor, Support Vector Machine, and Random Forest (namely KSR) by intersecting their results. Using SI markers improved the identification accuracy compared to using SNPs or InDels alone. We achieved accuracies over 97.5% when using at least the 1000 most breed-informative (MBI) SI markers and even 100% when using 5000 SI markers. Conclusions: Our results provide not only an important foundation for conservation of these Chinese local sheep breeds, but also general approaches for breed identification of indigenous farm animal breeds. [ABSTRACT FROM AUTHOR]

Hu sheep is a renowned prolific local sheep breed in China, widely distributed across the country due to its excellent reproductive performance. Deciphering the molecular mechanisms underlying the high fecundity of Hu sheep is crucial for improving the litter size of ewes. In this study, we genotyped 830 female Hu sheep using the Illumina OvineSNP50 BeadChip and performed genetic diversity analysis, selection signature detection, and a genome-wide association study (GWAS) for litter size. Our results revealed that the Hu sheep population exhibits relatively high genetic diversity. A total of 4927 runs of homozygosity (ROH) segments were detected, with the majority (74.73%) being short in length. Different genomic inbreeding coefficients (FROH, FHOM, FGRM, and FUNI) ranged from −0.0060 to 0.0126, showing low levels of inbreeding in this population. Additionally, we identified 91 candidate genomic regions through three complementary selection signature methods, including ROH, composite likelihood ratio (CLR), and integrated haplotype score (iHS), and annotated 189 protein-coding genes. Moreover, we observed two significant SNPs related to the litter size of Hu sheep using GWAS analysis based on a repeatability model. Integrating the selection signatures and the GWAS results, we identified 15 candidate genes associated with litter size, among which BMPR1B and UNC5C were particularly noteworthy. These findings provide valuable insights for improving the reproductive performance and breeding of high-fecundity lines of Hu sheep. [ABSTRACT FROM AUTHOR]

Infections with gastrointestinal nematodes on pasture have negative impact on animal health and production. Anthelmintics are used for deworming to prevent an excessive increase in parasite load and to treat parasitosis. Due to the progressive resistance of gastrointestinal nematodes to anthelmintics, their effectiveness is increasingly reduced. For this reason, alternatives are needed to combat infections with gastrointestinal nematodes. A sustainable strategy with great potential is the breeding of sheep with increased immunocompetence against gastrointestinal nematodes. Various indicators of gastrointestinal nematode infection can and should be used as selection traits for this purpose. Given the multifactorial background of infection events, the interpretation of the data and the definition of adequate breeding goals are particularly challenging. This review article deals with established and putative selection traits for breeding sheep with improved immunocompetence regarding gastrointestinal nematodes. With reference to the current state of sheep breeding in Germany, the challenges, especially with regard to the definition of breeding goals and phenotyping, are identified. The article ends with suggestions for possible first and further steps for German sheep breeding. [ABSTRACT FROM AUTHOR]

Objective: Qianhua Mutton Merino sheep is a new breed of meat wool sheep cultivated independently in China. In 2018, it was approved by the state and brought into the national list of livestock and poultry genetic resources. Qianhua Mutton Merino sheep have the common characteristics of typical meat livestock varieties with rapid growth and development in the early stage and high meat production performance. The objective of this research is to investigate the Genome-wide association of the reproductive traits of Qianhua Mutton Merino sheep. Methods: Qianhua Mutton Merino sheep from the breeding core group were selected as the research object, genome-wide association analysis was conducted on genes associated with the reproductive traits (singleton or twins, birth weight, age [in days] for sexual maturity, weaning weight, and daily gain from birth to weaning) of Qianhua mutton merino. Results: Our study findings showed that 151 loci of single-nucleotide polymorphisms (SNPs) were detected, among which 3 SNPs related to birth weight and weaning weight occupied a significant portion of the wide genome. The candidate genes preliminarily obtained were SYNE1, SLC12A4, BMP2K, CAMK2D, IMMP2L, DMD, and BCL2. Conclusion: We found 151 SNP loci for five traits related to reproduction (including singleton or twins, birth weight, age [in days] at sexual maturity, weaning weight, and daily weight gain from birth to weaning). The functions of these candidate genes were mainly enriched in nucleotide metabolism, metal ion binding, oxytocin signaling pathway, and neurotrophin signaling pathway. [ABSTRACT FROM AUTHOR]

In light of the escalating global concern regarding adaptation and resilience to elevated temperatures due to climate change, this experiment was designed to assess the thermo-physiological attributes of two native sheep breeds (Najdi and Naimi) and to delineate potential genetic factors conferring heat tolerance amidst acute exposure to elevated ambient temperatures. Meteorological and thermo-physiological parameters were scrutinized at distinct intervals (0 min, 30 min, 120 min, 24 hr, and 48 hr), alongside the analysis of heat-responsive gene expression at 0 min, 30 min, and 120 min, following the exposure of nine healthy male lambs from each breed (mean body weight: 25 kg; age: 4 months) to a bio-meteorologically-simulated environment, maintaining an average ambient temperature of 45 °C (approximately 93 units in the temperature-humidity index). In addition, blood samples were collected from each lamb, with total RNA isolated and purity assessed, followed by qRTPCR analysis of 16 heat stress candidate genes using validated primers and standardized thermocycling protocols, including controls to ensure accuracy. Data were analyzed using statistical methods, including PROC GLM and PROC MEANS in SAS, one-way ANOVA, and pairwise differences with the LSD test for significance, while gene expression differences were calculated using the comparative Ct method and 2 (-Ct) for relative quantification. The findings elucidate that the Najdi breed manifests heightened thermotolerance relative to the Naimi breed, as evidenced by diminished indicators of heat stress, encompassing skin temperature, respiratory rate, packed cell volume, adaptability coefficient, serum total protein, glucose levels, and triiodothyronine concentration. Moreover, analysis of gene expression patterns revealed widespread activation of heat stress-responsive genes in both breeds under thermal stress conditions; however, Najdi lambs consistently exhibited elevated expression levels of these genes compared to their Naimi counterparts. Notably, genes including HSP90AB1, HSPB6, HSF1, STIP1, HSP60, HSP90, and HSPB1 demonstrated particularly pronounced upregulation in Najdi lambs. In conclusion, the integrative thermo-physiological and molecular profiling highlights the superior thermotolerance and evolutionary adaptation of the Najdi breed to the hot climate of the KSA, in contrast to the Naimi breed. [ABSTRACT FROM AUTHOR]

This study analyzed the flavor compounds in the meat of four indigenous breeds of Chinese sheep through the use of gas chromatography–ion mobility spectrometry (GC-IMS). GC-IMS provided information on the characteristics and strength of 71 volatile flavor compounds (monomers and dimers), with aldehydes, alcohols and ketones being the most abundant in all types of sheep meat. The compounds with higher intensity peaks in the sheep meat were aldehydes (n-nonanal, octanal, heptanal, 3-methylbutanal, and hexanal), alcohols (1-octen-3-ol, hexanol, and pentanol), ketones (3-hydroxy-2-butanon, 2-butanone, and 2-propanone), esters (methyl benzoate), and thiazole (trimethylthiazole). The volatile flavor components in the meat of the different breeds of sheep obtained via GC-IMS were further differentiated using principal component analysis. In addition, orthogonal partial least squares discriminant analysis (OPLS-DA) and variable importance on projection (VIP) were used to determine the characteristic flavor compounds in the meats of different breeds of sheep, and 21 differentially volatile components were screened out based on having a VIP above 1. These results indicate that GC-IMS combined with multivariate analysis is a convenient and powerful method for characterizing and discriminating sheep meat. [ABSTRACT FROM AUTHOR]

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The present study aimed to identify the selection signature associated with temperature adaptation in Iranian sheep breeds raised in cold and hot environments. The Illumina HD ovine SNP600K BeadChip genomic arrays were utilized to analyze 114 animals from eight Iranian sheep breeds, namely Ghezel, Afshari, Shall, Sanjabi, Lori-Bakhtiari, Karakul, Kermani, and Balochi. All animals were classified into two groups: cold-weather breeds and hot-weather breeds, based on the environments to which they are adapted and the regions where they have been raised for many years. The unbiased FST (Theta) and hapFLK tests were used to identify the selection signatures. The results revealed five genomic regions on chromosomes 2, 10, 11, 13, and 14 using the FST test, and three genomic regions on chromosomes 10, 14, and 15 using the hapFLK test to be under selection in cold and hot groups. Further exploration of these genomic regions revealed that most of these regions overlapped with genes previously identified to affect cold and heat stress, nervous system function, cell division and gene expression, skin growth and development, embryo and skeletal development, adaptation to hypoxia conditions, and the immune system. These regions overlapped with QTLs that had previously been identified as being associated with various important economic traits, such as body weight, skin color, and horn characteristics. The gene ontology and gene network analyses revealed significant pathways and networks that distinguished Iranian cold and hot climates sheep breeds from each other. We identified positively selected genomic regions in Iranian sheep associated with pathways related to cell division, biological processes, cellular responses to calcium ions, metal ions and inorganic substances. This study represents the initial effort to identify selective sweeps linked to temperature adaptation in Iranian indigenous sheep breeds. It may provide valuable insights into the genomic regions involved in climate adaptation in sheep. [ABSTRACT FROM AUTHOR]

Simple Summary: In the last years, many domesticated and wild animal species, as well as local and transboundary breeds, have been threatened with genetic depletion and extinction. The application of conservation strategies to sheep breeds is necessary to safeguard the productive characteristics but also the historical and cultural value that they exert on their territory and inhabitants. Despite many advances that have been made in gamete cryopreservation, in vitro embryo production (IVEP) and juvenile in vitro production (JIVET), the efficiency of these technologies is still low, and the application is restricted in the ovine species. In the present study, a high concentration-rapid exposure (HC-RE) and a low concentration-slow exposure (LC-SE) vitrification protocol, using dimethyl sulfoxide (DMSO) and ethylene glycol (EG) as permeating cryoprotectants (CPAs), were applied to pre-pubertal lamb immature cumulus–oocyte complexes (COCs) and evaluated on nuclear and cytoplasmic parameters after in vitro maturation (IVM). Slightly more encouraging results were observed with the LC-SE vitrification protocol, leading to the hypothesis that low CPA concentrations in association with prolonged exposure times could be more promising to pursue in order to improve pre-pubertal lamb immature COC vitrification. Oocyte vitrification allows for the storing of endangered breed female gametes. Cryoprotectant (CPA) concentration and exposure time should ensure cell protection with minimal toxicity. In the present study, a high concentration-rapid exposure (HC-RE) and a low concentration-slow exposure (LC-SE) vitrification protocol, using dimethyl sulfoxide (DMSO) and ethylene glycol (EG) as permeating CPAs, were evaluated on meiotic competence and bioenergetic-oxidative status of pre-pubertal lamb immature COCs after in vitro maturation (IVM). For each protocol, COCs vitrified through a traditional protocol and fresh ones were used as controls. Both protocols allowed COC morphology preservation after vitrification-warming (V-W) and cumulus expansion after IVM. The maturation rate (7% and 14%) was comparable to the vitrified control (13% and 21%) but not satisfactory compared to fresh ones (58% and 64%; p < 0.001). The rate of mature oocytes displaying a perinuclear/subcortical (P/S) mitochondrial distribution pattern, an index of cytoplasmic maturity, was comparable between vitrified and fresh oocytes. The LC-SE vitrification protocol did not affect quantitative bioenergetic-oxidative parameters compared to both controls whereas HC-RE protocol significantly reduced intracellular reactive oxygen species (ROS) levels, indicating cell viability loss. In conclusion, to improve pre-pubertal lamb immature COC vitrification, the combination of low CPA concentrations with prolonged exposure time could be more promising to investigate further. [ABSTRACT FROM AUTHOR]

Simple Summary: California was the second largest sheep-producing state in the US, with an inventory of 533,000 head of sheep and lambs in 2022. Mastitis is a health and welfare concern for ewes and lambs. Mastitis is one of the top reasons for the removal of ewes from the flock and antibiotic use in ewes. In this study, California sheep producers were surveyed on the management of ewes. Seventy-one surveys were completed. Most respondents had flocks of ≥100 sheep (54%; 38/71). Twenty-three percent (16/70) of the respondents reported having >5% udder abnormalities in a flock per lactation. Further analysis showed two clusters among participating farms. Larger flock sizes, the use of breeding ewes for meat or wool production or contract grazing, and more extensive management practices were associated with >5% udder abnormalities and ≥5% orphan lambs. A subset of the respondents (20) participated in serological testing for small ruminant lentivirus (SRLV) in sheep. A total of 1106 ewes or ewe lambs were sampled. The ewe-level seroprevalence was 14.1% (183/1106), and the flock-level seroprevalence was 75% (15/20) of the sampled farms. Our results describe flock demographics, management practices, and producer-reported udder health abnormalities in California ewes. Larger flock sizes and extensive management practices could be risk factors for udder abnormalities in ewes. (1) Background: Information is lacking on small ruminant lentivirus (SRLV) status, prevalence, risk factors, and control measures for mastitis in California ewes. The goal of this survey was to outline characteristics of the sheep industry in California related to udder health and mastitis management. (2) Methods: An online survey consisting of 48 questions was completed by respondents between April 2022 and February 2023. Descriptive analysis and chi-squared tests were conducted to evaluate associations between variables. A multiple correspondence analysis (MCA) of general management practices, udder health management, and flock demographics was performed to assess clustering. A subset of respondents (20) participated in SRLV serology testing. (3) Results: Seventy-one completed surveys were submitted. The MCA showed two clusters. Larger flock sizes, the use of breeding ewes for meat or wool production or contract grazing, and extensive management practices were more closely related to >5% udder abnormalities per lactation and ≥5% orphan lambs. The flock-level seroprevalence of SRLV was 75% (15/20), and ewe-level seroprevalence was 14.1% (183/1106). (4) Conclusions: The results of this study highlight areas that need further research, such as exploring differences in mastitis and SRLV incidences among management systems, the efficacy of mastitis treatments, and education on critical timepoints for mastitis diagnosis and control. [ABSTRACT FROM AUTHOR]

Introduction: Prolificacy has become an important breeding goal in sheep farming to increase farm profitability. With the adoption of improved genetics and management practices leading to increased lambing percentages, the proportion of triplet-born lambs has also increased on farms. However, mortality rates of triplet lambs are higher than for single- and twin-born lambs, and additional management inputs may be needed to support survival. The aim of this study was to identify factors that affect management practices that are considered important for triplet lamb survival by commercial farmers from the United Kingdom (UK), the Ireland (IRE), and New Zealand (NZ). Methods: An online survey was developed and disseminated to farmers in each country, focusing on farmer demographics, flock characteristics, management practices and production outcomes. A total of 448 farmers completed the survey, from the UK (n = 168), IRE (n = 218), and NZ (n = 62). Results: Respondents had larger flocks, higher scanning and lambing percentages than the country average for the UK and IRE. The mean percentage of triplet litters born within flocks was 9%, and lambs lost between scanning and lambing were 14% for UK, 15% for IRE, and 25% for NZ respondents (P = 0.063). Overall, 60% of all respondents reported to lamb indoors and 40% lambed outdoors, however NZ farmers almost exclusively lambed outdoors, whereas UK and IRE farmers lambed in both systems (P < 0.001). NZ farmers were more likely to rear all triplet lambs with the ewe, whereas UK and IRE farmers were more likely to remove a lamb to rear by another ewe or artificially (P < 0.001). Factors that influenced triplet lamb management practices of respondents in this study were respondent country of origin, flock size, age, and gender. In general, younger respondents (P < 0.001), and female respondents (P < 0.05), were more likely to engage in management activities that were considered to promote better triplet lamb survival, compared to older and male respondents respectively. These practices were associated with better lamb survival reported by respondents but were less likely to be carried out when flock size increased (P < 0.001). Discussion: The results of this survey highlight future priorities or communication strategies needed to improve triplet lamb survival. [ABSTRACT FROM AUTHOR]

In this study, a parametric programming model was developed in order to deliver optimal management plans for various types of farms rearing endangered Greek sheep breeds under three distinct scenarios. The first scenario investigated the optimal internal organization of farms (i.e., management practices and resource allocation strategies that increase profitability of farms) under current market conditions (e.g., product prices) without, however, considering subsidies and compensations. The second assessed the impact of an agri-environmental support scheme on farm optimal structure and socioeconomic performance. The third investigated the effects of integrating farms into value chains and niche markets where premium prices prevail. For this purpose, a questionnaire survey was conducted in the wider region of Epirus and Thessaly, collecting management data from 16 farms rearing (i) Kalaritiko, (ii) Orino Epiru and (iii) Katsika rare sheep breeds. The main finding of this study was that the optimal internal organization of farms is essential for their self-reliance and viability. Therefore, it should be the basis in the designing of any initiative aimed at the preservation and valorization of local breeds. Furthermore, the analysis showed that a niche marketing strategy (i.e., a premium price strategy) can have a broader positive impact on farms structure and socioeconomic performance, particularly those engaged in cheese production, compared to an agri-environmental scheme. However, due to the fact that both initiatives possess limitations that may render them inefficient under specific external conditions, the development of an integrated incentive mechanism, which will combine both policy schemes and market-based initiatives, appeared to be a more effective strategy for the long-term viability of farms. [ABSTRACT FROM AUTHOR]

Introduction: T-sheep and H-sheep exhibit different environmental adaptability and production performance. The rumen microbiome has co-evolved with hosts and plays a vital role in nutrient digestion and energy metabolism. In our previous study, we found that T-sheep have a higher efficiency in energy metabolism than H-sheep, but the rumen microbial community remains unclear. Methods: In this study, we determined the rumen bacterial profile and rumen fermentation parameters to reveal the bacterial profiles and predictive functions among breeds and diets with four different energy levels, as well as the correlation between bacterial profiles and rumen fermentation characteristics. Results: The results showed that the rumen total volatile fatty acids (VFAs), acetate, butyrate, total branched-chain VFAs, iso-butyrate, and iso-valerate were higher in T-sheep than H-sheep. The alpha diversity of ruminal bacteria is not affected by dietary energy, but it shows a distinction between the sheep breeds. Specifically, T-sheep rumen bacteria exhibit higher alpha diversity than H-sheep. The beta diversity of ruminal bacteria is not influenced by dietary energy or sheep breeds, indicating similar communities of ruminal bacteria between different diets and sheep breeds. The phyla of Bacteroidetes and Firmicutes predominate in the rumen, with a higher relative abundance of Firmicutes observed in T-sheep than H-sheep. The two most abundant genera in the rumen were Prevotella 1 and Rikenellaceae RC9 gut group. Prevotella 1 is the predominant bacterial genus in the rumen of H-sheep, while the Rikenellaceae RC9 gut group dominates in the rumen of T-sheep. Microbial co-occurrence network analysis reveals that variations in rumen fermentation characteristics result from differences in module abundance, with a higher abundance of VFA-producing modules observed in the rumen of T-sheep. Microbial function prediction analysis showed that dietary energy rarely alters the functional composition of rumen bacteria. However, there were differences in the functions of rumen bacteria between sheep breeds, with T-sheep showing a greater emphasis on energy metabolism-related functions, while H-sheep showed a greater emphasis on protein metabolism-related functions. Discussion: These findings provide evidence of the special rumen microbial community that helps T-sheep efficiently obtain energy from low-protein and low-energy diets, enabling them to survive in the extreme environment of the Qinghai–Tibet Plateau. [ABSTRACT FROM AUTHOR]

The Booroola fecunditymutation (FecB) in Small Tail Han sheep has been shown to enhance ovulation rates and litter sizes by affecting the hypothalamic-pituitary-gonadal (HPG) axis. Despite the pituitary's role in reproductive regulation, its involvement in FecB-induced ovulation remains understudied. Our study aimed to fill this gap by analyzing pituitary tissues from FecB homozygous (BB) and wildtype (WW) ewes during luteal and follicular phases using tandem mass tag-based protein quantification and the DIABLO framework for proteomic and transcriptomic data integration. Significant differences in 277 proteins were observed across estrus periods, with network analysis highlighting the voltagedependent calcium channel L-type alpha-1C as a key convergence point in oxytocin signaling and GnRH secretion pathways. The DIABLO method revealed a strong correlation (0.98) between proteomic and transcriptomic datasets, indicating a coordinated response in FecB ewes. Notably, higher expression levels of Follicle Stimulating Hormone Subunit Beta (FSHB) and Luteinizing Hormone Subunit Beta (LHB) were found in BB ewes during the follicular phase, potentially due to elevated E2 concentrations. Furthermore, our analysis identified genes related to the Gamma-aminobutyric acid type A receptor family (GABRA2, GABRG1, GABRB1) in the pituitary, with GABRB1 showing higher expression in BB ewes. This suggests a role for GABA in modulating GnRH and gonadotropin feedback loops, potentially contributing to the FecB mutation's effect on ovulation. This study provides novel insights into the pituitary's role in fertility among FecB sheep, identifying GABA as a potential regulatory factor within the HPG axis. The findings also open avenues for discovering new biomarkers in pituitary endocrinology for sheep breeding purposes. [ABSTRACT FROM AUTHOR]

Background: This study aims to determine the relationship between milk composition traits and breed in the Akkaraman and Awasi sheep as well as to provide ease of interpretation by showing the relationships structure between variables and between categories of variables in two-dimensional space with Categorical principal component analysis. Methods: Categorical principal component analysis determines relationships between continuous and categorical variables as well as ordinal variables. It aims to reduce system dimensionality through optimal scaling while maintaining variable measurement levels (nominal, multiple nominal, ordinal and interval). In this research, data obtained from Akkaraman and Awasi Breed Sheep Raised by Public Hands in Tuşba District of Van Province were used. In order to determine relationship with breed, the traits were divided into two categories, "low" and "high" and all variables (9 variables) were considered together and a Categorical principal components analysis was performed. Result: As a results, Dimension 1 accounted for 35.58% of the total variation while dimension 2 accounted for 15.21%. Two dimensions together accounted for 50.79% of the variation. Thus it can be noted that Categorical principal component analysis can be used in the analysis of data sets containing a large number of different types of variables with linear or non-linear relationships between them. [ABSTRACT FROM AUTHOR]

Simple Summary: α-keratins are the main structural proteins in the cortex of wool fibres. Variation in these proteins affects the structure and fibre characteristics of wool, making keratin genes good candidates for the development of gene markers to selectively breed for better wool. Variation was found in the keratin gene KRT85, with the presence of the A variant being associated with an increase in greasy fleece weight and clean fleece weight, and the presence of B associated with an increased wool prickle factor. This may assist in the development of gene markers to assist in sheep breeding. 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. [ABSTRACT FROM AUTHOR]

Simple Summary: The melanocortin 4 receptor (MC4R) is an important gene that can affect the growth and economic traits of sheep. This study first investigated the distribution of the MC4R gene's p.T117M mutation in sheep breeds worldwide. The results showed that the mutation's frequency was higher in European breeds compared with Chinese sheep breeds. The p.T117M mutation occurs in the first extracellular loop of MC4R. Mechanistically, the basal activity of the mutated receptor significantly increased. Specifically, upon treatment with α-MSH and ACTH ligands, the cAMP and MAPK/ERK signaling activation of M117 MC4R was enhanced. These results indicate that the T117M mutation may change the function of the gene by increasing the constitutive activity and signaling activation of cAMP and MAPK/ERK, and, thus, may regulate the growth traits of sheep. This may provide effective assistance for improving the economic benefits of the sheep industry. The melanocortin 4 receptor (MC4R) gene plays a central role in regulating energy homeostasis and food intake in livestock, thereby affecting their economic worth and growth. In a previous study, the p.T117M mutation in the sheep MC4R gene, which leads to the transition of threonine to methionine, was found to affect the body weight at six months and the average daily gain in Hu sheep. However, there are still limited studies on the frequency of the sheep p.T117M missense mutation globally, and the underlying cellular mechanism remains elusive. Therefore, this study first used WGS to investigate the distribution of the MC4R gene p.T117M mutation in 652 individuals across 22 breeds worldwide. The results showed that the mutation frequency was higher in European breeds compared with Chinese sheep breeds, particularly in Poll Dorset sheep (mutation frequency > 0.5). The p.T117M mutation occurs in the first extracellular loop of MC4R. Mechanistically, the basal activity of the mutated receptor is significantly increased. Specifically, upon treatment with α-MSH and ACTH ligands, the cAMP and MAPK/ERK signaling activation of M117 MC4R is enhanced. These results indicate that the T117M mutation may change the function of the gene by increasing the constitutive activity and signaling activation of cAMP and MAPK/ERK, and, thus, may regulate the growth traits of sheep. In conclusion, this study delved into the global distribution and underlying cellular mechanisms of the T117M mutation of the MC4R gene, establishing a scientific foundation for breeding sheep with superior growth, thereby contributing to the advancement of the sheep industry. [ABSTRACT FROM AUTHOR]

Simple Summary: The horned type of sheep, including the polled phenotype and scurs phenotype, emerged during the process of artificial domestication. Sheep serve as an optimal animal model for investigating the correlation between quality and quantity traits of horns, as well as the multi-gene regulatory mechanism underlying these traits. While significant progress has been made in understanding the effects of natural selection and sex selection on horn phenotypes, there is limited research on polymorphisms resulting from artificial selection. Through genome-wide association analysis, this study reveals the genetic mapping of horn phenotypes, polled genes, and superior haplotypes to provide valuable insights into studying the genetic mechanisms governing horn traits and other specific characteristics in ruminants while also laying a foundation for breeding. The types and morphology of sheep horns have been extensively researched, yet the genetic foundation underlying the emergence of diverse horn characteristics during the breeding of polled Tibetan sheep has remained elusive. Genome-wide association analysis (GWAS) was performed on 103 subtypes (normal large horn, scurs, and polled) differentiated from G2 (offspring (G2) of parent (G1) of polled) of the polled core herd. Six single nucleotide polymorphisms (SNPs) located on chromosome 10 of the relaxin family peptide receptor 2 (RXFP2) gene exhibited positive correlations with horn length, horn base circumference, and horn base interval. Furthermore, in genotyping 382 G2 individuals, significant variations were observed for each specific horn type. Three additional mutations were identified near the target SNP upstream of the amplification product. Finally, the RXFP2-specific haplotype associated with the horned trait effectively maintained horn length, horn base circumference, and horn base interval in Tibetan sheep, as confirmed by population validation of nine loci in a sample size of 1125 individuals. The present study offers novel insights into the genetic differentiation of the horned type during improvement breeding and evolution, thereby establishing a robust theoretical foundation for polled Tibetan sheep breeding and providing valuable guidance for practical production. [ABSTRACT FROM AUTHOR]

Domestic animals have multiple phenotypes of skin and coat color, which arise from different genes and their products, such as proteins and metabolites responsible with melanin deposition. However, the complex regulatory network of melanin synthesis remains to be fully unraveled. Here, the skin and tongue tissues of Liangshan black sheep (black group) and Liangshan semi-fine-wool sheep (pink group) were collected, stained with hematoxylin–eosin (HE) and Masson–Fontana, and the transcriptomic and metabolomic data were further analyzed. We found a large deposit of melanin granules in the epidermis of the black skin and tongue. Transcriptome and metabolome analysis identified 744 differentially expressed genes (DEGs) and 443 differentially expressed metabolites (DEMs) between the pink and black groups. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses revealed the DEGs and DEMs were mainly enriched in the pathways of secondary metabolic processes, melanin biosynthesis processes, melanin metabolism processes, melanosome membranes, pigment granule membranes, melanosome, tyrosine metabolism, and melanogenesis. Notably, we revealed the gene ENSARG00020006042 may be a family member of YWHAs and involved in regulating melanin deposition. Furthermore, several essential genes (TYR, TYRP1, DCT, PMEL, MLANA, SLC45A2) were significantly associated with metabolite prostaglandins and compounds involved in sheep pigmentation. These findings provide new evidence of the strong correlation between prostaglandins and related compounds and key genes that regulate sheep melanin synthesis, furthering our understanding of the regulatory mechanisms and molecular breeding of pigmentation in sheep. [ABSTRACT FROM AUTHOR]

Climate change and heat stress pose significant challenges to livestock. Local breeds, particularly small ruminants, are gaining importance due to their adaptability to harsh climates. However, the extensive system they are commonly reared in leaves them exposed to the effects of climate change. This study aims to describe the distribution and climate-related challenges faced by registered Italian sheep and goat breeds over the past seven decades. Geolocalized data from all registered small ruminant farms were combined with climatic information retrieved from the "ERA-5-Land hourly data from 1950 to present" dataset. These data were used to calculate average daily temperature, temperature humidity index (THI), and total precipitation during summer. Additionally, THI-based heat waves (HWs) were examined, including the yearly number of HW days and mean THI during HW days. These data were analysed through linear regression models including region or breed, year, and their interaction as fixed factors. The climate data indicate a concerning trend of rising summer temperatures, THI, and HW frequency and intensity, particularly over the past three decades. Central-northern Italy, including the Po Valley and the Alpine Arch, is the most affected region, impacting breeds like Rosset and Brogne sheep, and Lariana and Frisa Valtellinese goats. This is of particular concern because these populations have not been selected for hot climates, and their already small population size exacerbates the problem. Conversely, southern Italy, characterized by hotter and drier temperatures, remained relatively stable. Breeds from this region, such as Girgentana and Nicastrese goats and Nera di Arbus sheep, might represent excellent case studies for climatic adaptation and potential resources for selection for resilience in the face of ongoing climate changes. The findings presented here are essential for the development of monitoring and intervention strategies for breeds facing future vulnerabilities, as well as for designing experiments to explore environmental adaptability in small ruminants. [ABSTRACT FROM AUTHOR]

Simple Summary: Considering the global decline in local sheep genetic resources, we conducted the current study to assess the status and quality of Hungarian native sheep breed genetic resources stored in a small Gene Bank established between 2014 and 2017. Semen samples from 24 rams of different breeds were collected during the breeding season and out of season using an artificial vagina, cryopreserved manually. Frozen/thawed spermatozoa were evaluated for motility and kinematic parameters, viability, chromatin structure, and morphometry of the sperm nuclei. We observed breed, season, and individual ram effects on the motility, kinematics, viability, and morphometrical parameters of the post-thaw spermatozoa samples stored in the Gene Bank. The stored samples are of good quality, and the cryopreservation technique adopted for the small Gene Bank proved promising for conserving the genetic resources of the native Hungarian sheep, as it resulted in acceptable post-thaw parameters. To maintain rare and valuable genotypes, cryo-conservation of not only spermatozoa but also oocytes and embryos is needed. Therefore, we plan to implement an extended gene conservation program involving a more significant number of individuals of native Hungarian sheep breeds. Studies revealed a global loss of genetic resources for local sheep breeds. Therefore, the current study aimed to introduce and highlight the progress made on Hungary's existing gene conservation program (small Gene Bank). Furthermore, we evaluated breed (Tsigai, Cikta, and Racka), season, and individual variabilities (n = 24) of the pre-freeze and post-thaw semen stored in the Gene Bank to enhance the gene conservation of the breeds. The samples were cryopreserved manually, and post-thaw spermatozoa were analyzed for motility (CASA), viability, chromatin structure, and morphometry of the sperm nuclei. Ejaculate volume, spermatozoa concentration, subjective motility and standard motility, kinematic parameters, and spermatozoa's head area standard deviation of the post-thaw samples differed significantly among breeds (p < 0.05). Season affected ejaculate volume, total spermatozoa number/ejaculate, STR, BCF, and ALH. We observed a significant (p < 0.001; 0.05) breed and season interaction on concentration, total spermatozoa number/ejaculate, VCL, LIN, WOB, spermatozoa's head average perimeter and nucleus length (Tsigai and Cikta differed but were statistically the same as Racka). Similarly, season significantly (p < 0.05) affected the proportion of ejaculate suitable for freezing. There was a significant (p < 0.05) difference in kinematic parameters and viability among the rams across the breeds. The spermatozoa's head morphometry of the Tsigai and Cikta breeds differed significantly (p < 0.05) among the rams. There were individual and breed differences in many spermatozoa quality parameters. The stored samples are of good quality, with more than 40% having intact membranes and low abnormal chromatin condensation. [ABSTRACT FROM AUTHOR]

Background: Managing 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). Results: Katahdin 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. Conclusions: In 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. [ABSTRACT FROM AUTHOR]

Background: Litter size plays a crucial role in determining profitability in the sheep industry. Breeding sheep with high litter sizes could be enhanced by selecting candidate genes. One gene affecting sheep's reproductive performance is the hormone-sensitive lipase (HSL) gene. As a result, this study investigated whether the HSL gene variation influenced the fertility of Awassi ewes. The genomic DNA was extracted from 52 singleton ewes and 48 twin ewes. The HSL gene exon 9 (278 bp) was amplified using polymerase chain reaction (PCR). Results: Study results revealed two genotypes identified in the 278-bp amplicons: GG and GA. Molecular sequence analysis identified a novel mutation in the GA genotype 216G > A. The statistical analysis revealed a significant association between the single nucleotide polymorphism (SNP) 216A > G and reproductive performance. Ewes with the SNP 216G > A genotype exhibited significantly increased litter sizes, twinning rates, lambing rates, and fewer days to lambing compared to ewes with GG genotypes (P ≤ 0.05). The logistic regression analysis results provided strong evidence that the 216G > A mutation significantly increased litter sizes. Conclusions: This study concluded that variant 216G > A SNP positively impacts Awassi sheep reproduction. There is a higher litter size and more prolificacy in ewes with the 216G > A SNP than in those without the SNP. [ABSTRACT FROM AUTHOR]

Numerous studies have indicated that Morocco's indigenous sheep breeds are genetically homogenous, posing a risk to their survival in the challenging harsh climate conditions where they predominantly inhabit. To understand the genetic behind genetic homogeneity through the lens of runs of homozygosity (ROH), we analyzed the whole genome sequences of five indigenous sheep breeds (Beni Guil, Ouled Djellal, D'man, Sardi, Timahdite and Admixed).The results from principal component, admixture, Fst, and neighbour joining tree analyses consistently showed a homogenous genetic structure. This structure was characterized by an average length of 1.83 Mb for runs of homozygosity (ROH) segments, with a limited number of long ROH segments (24–48 Mb and > 48 Mb). The most common ROH segments were those ranging from 1–6 Mb. The most significant regions of homozygosity (ROH Islands) were mostly observed in two chromosomes, namely Chr1 and Chr5. Specifically, ROH Islands were exclusively discovered in the Ouled Djellal breed on Chr1, whereas Chr5 exhibited ROH Islands in all breeds. The analysis of ROH Island and iHS technique was employed to detect signatures of selection on Chr1 and Chr5. The results indicate that Chr5 had a high level of homogeneity, with the same genes being discovered across all breeds. In contrast, Chr1 displays some genetic variances between breeds. Genes identified on Chr5 included SLC39A1, IL23A, CAST, IL5, IL13, and IL4 which are responsible for immune response while genes identified on Chr1 include SOD1, SLAMF9, RTP4, CLDN1, and PRKAA2. ROH segment profile and effective population sizes patterns suggests that the genetic uniformity of studied breeds is the outcome of events that transpired between 250 and 300 generations ago. This research not only contributes to the understanding of ROH distribution across breeds but helps design and implement native sheep breeding and conservation strategies in Morocco. Future research, incorporating a broader sample size and utilizing the pangenome for reference, is recommended to further elucidate these breeds' genomic landscapes and adaptive mechanisms. [ABSTRACT FROM AUTHOR]

Simple Summary: Recently, the escalating prices of feedstuff resources have posed significant challenges to animal husbandry, necessitating the creation of innovative approaches to mitigate its effects. GAA (also known as N-amidinoglycine) serves as the sole precursor for creatine synthesis. GAA could enhance growth performance and regulate fat deposition to improve meat quality. Current studies on GAA mainly center on pigs and chickens, with limited reports on its effects on sheep. In our study, we used weaned Hu sheep as subjects. We aimed to explore the impact of dietary GAA supplementation on production performance, serum biochemistry, meat quality and rumen fermentation. This study provides a theoretical foundation for utilizing GAA in sheep meat production. Our findings indicate that GAA enhances growth performance, rumen fermentation and fat accumulation. In addition, GAA might enhance the quality of sheep meat, which presents a promising prospect for meat sheep breeding. Guanidinoacetic acid (GAA) can effectively improve the metabolism of energy and proteins by stimulating creatine biosynthesis. We present a study exploring the impact of GAA on production performance, serum biochemistry, meat quality and rumen fermentation in Hu sheep. A total of 144 weaned male Hu sheep (body weight 16.91 ± 3.1 kg) were randomly assigned to four groups with three replicates of twelve sheep in each group. The diets were supplemented with 0 (CON), 500 (GAA−1), 750 (GAA−2) and 1000 mg/kg (GAA−3) of GAA (weight of feed), respectively. After a comprehensive 90-day experimental period, we discovered that the supplementation of GAA had a remarkable impact on various muscle parameters. Specifically, it significantly enhanced the average daily growth (ADG) of the animals and improved the shear force and fiber diameter of the muscle, while also reducing the drip loss and muscle fiber density. Furthermore, the addition of GAA to the feed notably elevated the serum concentrations of high-density lipoprotein cholesterol (HDL−C), total protein (TP) and globulin (GLB), as well as the enzyme activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH−Px). Concurrently, there was a decrease in the levels of triglycerides (TG) and malondialdehyde (MDA) in the serum. In addition, GAA decreased the pH and the acetate-to-propionate ratio and increased the total volatile fatty acids (TVFA) and ammoniacal nitrogen (NH3−N) levels of rumen fluid. Additionally, GAA upregulated acetyl-CoA carboxylase (ACC) gene expression in the Hu sheep's muscles. In conclusion, our findings suggest that GAA supplementation not only enhances muscle quality but also positively affects serum biochemistry and ruminal metabolism, making it a potential candidate for improving the overall health and performance of Hu sheep. [ABSTRACT FROM AUTHOR]

Raising small ruminants is the main source of income for farmers in Pakistan especially in rural areas of Dera Ghazi Khan in Punjab. Despite having large sheep population, the prevalence of intra-erythrocytic protozoa, Theileria (T.) lestoquardi, has never been reported from this area. This study was conducted to fill this knowledge gap and 333 blood samples of apparently healthy small ruminants (168 sheep and 165 goats) along with their epidemiological data were collected from Dera Ghazi Khan district during August till November 2022. The polymerase chain reaction (PCR) analysis amplified a 785 base pair amplicon specific for the Merozoite surface antigen (ms 1–2) gene of T. lestoquardi in 2 out of the 168 (3.3%) sheep blood samples, while no goat blood sample out of 165 was found to be infected with T. lestoquardi. DNA sequencing confirmed the presence of Theileria lestoquardi in both samples and phylogenetic analysis revealed that these amplicon resembled the partial ms 1–2 gene sequences detected in small ruminants from Pakistan, India Iran and Egypt. All the studied epidemiological factors (age, sex, breed, size of herd, dogs with herd, composition of herd, size of herd and Tick burden on sheep) were not found associated with the prevalence of T. lestoquardi. In conclusion, this study reports a low prevalence of T. lestoquardi infection in the Dera Ghazi Khan District of Punjab, Pakistan. The data generated from this work will help pave the way for the prophylactic detection and control of ovine and caprine theileriosis in the region. [ABSTRACT FROM AUTHOR]

Analyzing the genetic diversity and selection characteristics of sheep (Ovis aries) holds significant value in understanding their environmental adaptability, enhancing breeding efficiency, and achieving effective conservation and rational utilization of genetic resources. In this study, we utilized Illumina Ovine SNP 50 K BeadChip data from four indigenous sheep breeds from the southern margin of the Taklamakan Desert (Duolang sheep: n = 36, Hetian sheep: n = 74, Kunlun sheep: n = 27, Qira black sheep: n = 178) and three foreign meat sheep breeds (Poll Dorset sheep: n = 105, Suffolk sheep: n = 153, Texel sheep: n = 150) to investigate the population structure, genetic diversity, and genomic signals of positive selection within the indigenous sheep. According to the Principal component analysis (PCA), the Neighbor-Joining tree (NJ tree), and Admixture, we revealed distinct clustering patterns of these seven sheep breeds based on their geographical distribution. Then used Cross Population Extended Haplotype Homozygosity (XP-EHH), Fixation Index (FST), and Integrated Haplotype Score (iHS), we identified a collective set of 32 overlapping genes under positive selection across four indigenous sheep breeds. These genes are associated with wool follicle development and wool traits, desert environmental adaptability, disease resistance, reproduction, and high-altitude adaptability. This study reveals the population structure and genomic selection characteristics in the extreme desert environments of native sheep breeds from the southern edge of the Taklimakan Desert, providing new insights into the conservation and sustainable use of indigenous sheep genetic resources in extreme environments. Additionally, these findings offer valuable genetic resources for sheep and other mammals to adapt to global climate change. [ABSTRACT FROM AUTHOR]

On pasture, sheep are exposed to infections with gastrointestinal nematodes. Infections with gastrointestinal nematodes cause damage to the animal and also have economic relevance. In order to avoid an excessive parasite load in the animal and to treat parasitosis, anthelmintics are used for deworming. However, gastrointestinal nematodes are becoming increasingly resistant to anthelmintics, making treatment less and less effective. Accordingly, alternative strategies are required to combat gastrointestinal nematodes. Breeding sheep with increased immunocompetence against gastrointestinal nematodes is a sustainable and long-term strategy. In order to proceed responsibly and effectively, the complexity of infections with gastrointestinal nematodes must be considered in more detail. This review article therefore deals with the infection, the effects of the infection on the animal, the immunological response shown by the animal, the acquired immunity to gastrointestinal nematodes as well as with parasite-host interactions. The article refers to the situation in Germany and concludes with a summary of the need for national action. [ABSTRACT FROM AUTHOR]

Genomic structural variants (SVs) constitute a significant proportion of genetic variation in the genome. The rapid development of long‐reads sequencing has facilitated the detection of long‐fragment SVs. There is no published study to detect SVs using long‐read data from sheep. We applied a long‐read mapping approach to detect SVs and characterized a total of 30,771 insertions, deletions, inversions and translocations. We identified 716, 916, 842 and 303 specific SVs in Southdown sheep, Alpine merino sheep, Qilian White Tibetan sheep and Oula sheep, respectively. We annotated these SVs and found that these SV‐related genes were primarily enriched in the well‐established pathways involved in the regulation of the immune system, growth and development and environmental adaptability. We detected and annotated SVs based on NGS resequencing data to validate the accuracy based on third‐generation detection. Moreover, five candidate SVs were verified using the PCR method in 50 sheep. Our study is the first to use a long‐reads sequencing approach to construct a novel structural variation map in sheep. We have completed a preliminary exploration of the potential effects of SVs on sheep. [ABSTRACT FROM AUTHOR]

This study was aimed to investigate the expression levels of transcription factor (TF) genes (MYF6, MYOD1, MYF5, MYOG) and proteins associated with muscle growth in the longissimus dorsi (LD) and gluteal (GL) muscles in sheep. For this aim, two fat-tailed sheep breeds (Akkaraman (n = 10), Awassi (n = 10)) and two thin-tailed sheep breeds (Kivircik (n = 10) and Karayaka (n = 10)) from Türkiye's native sheep breeds were examined. The expression level was analyzed for MYF6, MYOD1, MYF5, and MYOG genes and proteins that RNAs and proteins were isolated from fresh tissues. As a result of the statistical analysis, in the LD tissue, respectively, MYOG and MYF5 genes in the Karayaka sheep breed; MYOD1 gene in Akkaraman sheep breed; MYF5 gene in Awassi sheep breed were found to be significant (P < 0.05). In GL tissue, respectively, MYOG and MYF6 genes in Akkaraman sheep breed; MYOD1 gene in Karayaka sheep breed; MYF6 gene in Akkaraman and Awassi sheep breed were significant (P < 0.05). The MYOG (fold change 6.87) and MYOD1 (fold change 15.41) genes were upregulated in the GL muscle of the fat-tailed Akkaraman sheep breed. In addition, in the thin-tailed Karayaka sheep breed, down-regulation of MYOD1 (fold change –0.22) gene in LD muscle and up-regulation of MYOD1 (fold change 6.67) gene in GL muscle was found. As a result, it can be considered that MYOG and MYOD1 genes as potential candidate genes in molecular selection studies for Akkaraman sheep breed in terms of muscle development. [ABSTRACT FROM AUTHOR]

With a growing export and local market, sheep farming is critical to the economy of smallholder farmers; however, indigenous sheep breeds usually exhibit low carcass output and live weight due to nutritional constraints. The study aimed to investigate the impact of supplementing local sheep with dawri‐damaa leaf meal (DDLM) on their performance, carcass characteristics, and profitability when fed native grass hay. The research used a randomized complete block design (RCBD) to administer four feeding treatments (T1, T2, T3, and T4 at 0%, 30%, 50%, and 70% DDLM, respectively) to 20 local uncastrated male lambs having an average 23.72 ± 0.73 kg body weight and average age of 11.72 ± 0.74 months. Greater doses of DDLM in the diet resulted in greater average daily gain (ADG) of 51.4–83.8 g/day and feed conversion efficiency (FCE) of 0.066–0.089 in lambs, compared to 15.0 g/day ADG and 0.025 FCE in lambs under control diet (T1). Additionally, the lambs had increased slaughter body weight (SBW), empty body weight (EBW), and hot carcass weight (HCW) in T4 and T3 compared to other treatments (p <.05). There were no significant differences in dressing percentages (DPs) across any treatment group. The study also discussed the economic viability of supplementing with DDLM, suggesting that feeding 70% daily dry matter of DDLM at 2.5% live weight might be beneficial depending on availability, access, and cost factors. In conclusion, feeding DDLM up to 70% has improved the performance of sheep and is economically feasible. Further research might be required to discover whether such levels of inclusion are harmful and apply different processing methods for feeding animals. [ABSTRACT FROM AUTHOR]

Background: The comprehensive understanding of microRNAs (miRNAs) in sheep milk during various lactation periods and their impact on milk yield and composition remains limited. Objectives: This study aimed to investigate the expression patterns of four highly expressed miRNAs in sheep milk and their association with milk composition and yield parameters during peak and late lactation stages. Methods: A total of 40 healthy 4‐year‐old Akkaraman (n = 20) and Awassi (n = 20) ewes registered with the Ministry of Agriculture and Forestry of the Republic of Türkiye were used in the present study. For miRNA isolation from milk, the Qiagen miRNeasy Serum/Plasma Advanced Kit was utilised following the manufacturer's instructions. The expression levels of miRNAs were assessed using Qiagen miRNA PCR Assays. Results: The significant fold changes in the expression levels of oar‐miR‐30a‐5p, oar‐miR‐148a and oar‐miR‐181a were observed between peak and late lactation periods in the Awassi sheep breed. Conversely, only oar‐miR‐30a‐5p and oar‐miR‐148a exhibited statistically significant changes in the Akkaraman sheep breed during the same lactation periods. Furthermore, oar‐miR‐21‐5p demonstrated a significant fold change exclusively in peak lactation compared to Akkaraman and Awassi ewes. Conclusions: The findings suggest that the expression of the analysed miRNAs is influenced by both the lactation stage and different sheep breeds. This study offers valuable insights into the relationship between key miRNA expressions in sheep milk and milk composition and yield parameters during peak and late lactation, contributing to the existing knowledge in this field. [ABSTRACT FROM AUTHOR]

The social behaviour of twenty-one lambs of three sheep breeds (Chios, Karagouniki, and Synthetic) was observed from the age of 2.5–7 months, divided into three equal periods (A, B, C) of 1.5 months each. The frequency of the performed agonistic behaviours was higher (p < 0.01) before four months of age (period A: 11 × 10−4 ± 2 × 10−4) compared to the other periods (B: 5 × 10−4 ± 1 × 10−4; C: 8 × 10−4 ± 1 × 10−4). The same was noticed for affiliative behaviours performed (A: 21 × 10−4 ± 3 × 10−4; B: 8 × 10−4 ± 1 × 10−4; C: 5 × 10−4 ± 1 × 10−4), and for agonistic and affiliative behaviours received (p < 0.001). The lambs had higher levels of wool cortisol (23.398 ± 5.344 pg/mg; p < 0.01) at period C compared to A (7.899 ± 1.19 pg/mg). Breed affected the affiliative behaviours. Karagouniki showed higher frequencies than Synthetic (16 × 10−4 ± 3 × 10−4 vs. 6 × 10−4 ± 1 × 10−4). Blood cortisol was higher (p < 0.05) in the Synthetic (4.789 ± 0.928 ng/mL) compared to the Chios (1.805 ± 0.417 ng/mL) breed. Overall, lambs' behaviour displayed changes upon time, with four months of age being a step to a next developmental stage with fewer social interactions and higher levels of cortisol. [ABSTRACT FROM AUTHOR]

Meat from sheep offers an abundance of essential amino acids and trace elements essential for optimal human health and a delectable culinary delight. Because it has fewer calories and a lower cholesterol content than other meats, this succulent meat is not only delicious but also a nutritious choice. Globally, discriminating consumers have expressed profound appreciation for its irresistible flavor and nutritious composition. High-quality sheep breeds and lamb quality are in the spotlight as the market for sheep meat grows. Nevertheless, the demand for rapid growth and the use of antibiotics and other drugs have led to a shortage of high-quality mutton on the market. In the face of this emergency phenomenon, people add organic matter to the growth of mutton to improve the quality of mutton. This paper discusses the comprehensive evaluation methods of meat quality; summarizes the relationship between the nutritional components of meat and diet; discusses the genetic factors affecting meat quality attributes; feed nutrition, feeding methods, mutton storage methods, and related measures to improve the quality of mutton; and provides information on the current status of mutton and the challenges of ensuring high-quality meat supply in the future. [ABSTRACT FROM AUTHOR]

Simple Summary: The BMPR1B and T/Brachyury genes are considered major genetic factors influencing sheep reproduction and tail bone number. In this study, we conducted an association analysis between nine mutations of the BMPR1B gene and the litter sizes of short-tailed Gobi sheep and larger-tailed Ujimqin sheep. We also compared the frequency of the favorable alleles of four mutations among Gobi short tail sheep, Ujimqin sheep, and Mongolia sheep. In addition, we confirmed that the frequency of tail-bone-number-related T alleles at position c.363G>T in the T gene was significantly higher in short-tailed Gobi sheep than larger-tailed Ujimqin sheep. The significant deposition of tail fat in sheep has a profound impact on the economic benefits of animal husbandry. Furthermore, increasing the litter size is a crucial means of enhancing economic benefits. The BMPR1B and T/Brachyury genes are considered major functional genes that could affect sheep litter size and tail bone number, respectively. In this study, we employed direct sequencing to identify specific mutations of the BMPR1B gene in Gobi short tail sheep and carried out genotyping using MassARRAY technology for each variant of both the BMPR1B and T genes. Significant associations were demonstrated between the c.687G>A mutation of BMPR1B and the litter size in both the Gobi short tail sheep and Ujimqin sheep breeds. Meanwhile, the g.30058882_30058873GCAGATTAAAIndel mutation was significantly associated with the litter size in Gobi short tail sheep. These findings may provide valuable genetic markers for expanding sheep litter size. In addition, we also confirmed that the frequency of tail-bone-number-related T alleles was significantly higher in Gobi short tail sheep than in longer-tailed Ujimqin sheep. [ABSTRACT FROM AUTHOR]

Fasciolosis is an economically important disease in sheep, caused by the trematode, Fasciola, also known as liver fluke, belonging to the Class Trematoda (Phylum Platyhelminthes). In order to determine the prevalence of this fluke parasite, based on different risk factor(s) associated with sheep raised in pasture land of Kargil, Ladakh, a cross-sectional study was conducted on 410 faecal samples consisting of 148, 127 and 135 samples of local breeds Purgi, Cross breed (CB) Karakul and CB-Kashmiri Merino sheep respectively. Fresh faecal samples were taken directly from the rectum and brought in airtight polythene bags for parasitological examination to the Department of Sheep Husbandry Parasitology Laboratory, Kargil, Ladakh. The samples were examined through standard floatation and sedimentation techniques. The overall prevalence was found to be low (0.97%). Generally, the risk factors such as type of breed, was found to have a significant (p£0.05) influence on the risk of fasciolosis in the sheep whereas other factors viz., age, sex and season were found to have statistically non-significant (p>0.05) effect. According to breed, the infection was seen only in CB-Kashmiri Merino while with respect to age and sex, the higher infection was recorded in >2 year and in the female counterparts as compared to age 1-2 years and in the males. However, no infection was recorded in <1 year kids. Based on the influence of season, the higher infection (2.19%) was recorded in autumn, while lower infection (1.98%) was recorded in summer season. No infection was recorded in spring and winter seasons. The very low infection rates and absence of infection in native breeds like local Purgi and CB-Karakul sheep could be attributed to the absence of intermediate hosts in other regions of district Kargil because the infection was recorded only from Drass Valley, where the native flocks shared a pasture land with the exotic breeds of other states. The present study will be useful in comprehending the epidemiology of gastrointestinal helminths in small ruminants, particularly in resource-poor communities of cold dessert Ladakh and the findings of this study serve as a message to small-scale rearers/stakeholders to formulate a proper sustainable management system and avoid sharing grazing/breeding lands with exotic breeds in order to prevent the cross infection with GIT helminth parasites in their native sheep flocks. [ABSTRACT FROM AUTHOR]

The importance of the present study is contributing to a deeper understanding of the mechanisms and patterns of the genetic structure of sheep populations developed in specific agroecological conditions in the south of Russia in the evolution, consolidation of economically important phenotypic traits in the ontogenesis and increase in local breed's potential fulfilled, which is especially important when solving the problem of intensifying the sheep breeding industry. The method of genome-wide analysis was first applied to obtain data on the genetic parameters of Kalmyk fat-tailed, Edilbay, and Volgograd sheep populations bred in the South of Russia. Molecular inbreeding and genetic diversity of sheep were assessed. The average level of inbreeding was 2.72% for the Volgograd breed, 1.96% for the Kalmyk breed, and (-)0.0022 for the Edilbay breed. A genetic relationship between the Volgograd and Kalmyk breeds was not identified; large genome regions of the Kalmyk and Edilbay breeds were homologous; the Volgograd breed was genetically isolated. Based on the body weight data, an association analysis was performed to search for genes and genome regions associated with this trait. There were found 4 SNPs significantly associated with the indicated parameter (p

Objective: Rare disease. Background: Parinaud oculoglandular syndrome is a unilateral granulomatous palpebral conjunctivitis associated with preauricular, submandibular, and cervical lymphadenopathies. Several infectious diseases can cause Parinaud oculoglandular syndrome, usually with a conjunctival entry. The most common underlying pathology is cat scratch disease, followed by the oculoglandular form of tularemia. Diagnosis is usually a serious challenge as these infections are themselves rare. On the other hand, Parinaud oculoglandular syndrome may be a rare manifestation of more common disorders (eg, tuberculosis, syphilis, mumps, herpes simplex and Epstein-Barr virus, adenovirus, Rickettsia, Sporothrix, Chlamydia infections). Case Report: We present the case of a 66-year-old man with granulomatous conjunctivitis and ipsilateral preauricular, submandibular, and upper cervical lymphadenopathies following a superficial corneal injury. Although the systematic amoxicillin/clavulanic acid and metronidazole antibiotic therapy started immediately at admission, the suppuration of the lymph nodes required surgical drainage. Based on his anamnesis (sheep breeding; a twig scratching his eye 2 days before the initial attendance) and symptoms, a zoonosis, namely the oculoglandular form of tularemia, was suspected, empiric ciprofloxacin therapy was administered, and the patient recovered without sequelae. The Francisella tularensis infection was eventually confirmed by microagglutination serologic assay. Conclusions: If Parinaud oculoglandular syndrome is diagnosed and cat scratch fever as the most common etiology is not likely, other zoonoses, especially the oculoglandular form of tularemia, should be suspected. Serology is the most common laboratory method of diagnosing tularemia. Empiric fluoroquinolone (ciprofloxacin) or aminoglycoside (gentamicin or streptomycin) antibiotic therapy should be started immediately at the slightest suspicion of oculoglandular tularemia. [ABSTRACT FROM AUTHOR]

Guide Black-Fur sheep (GD) is a breed of Tibetan sheep (Ovis aries) that lives in the Qinghai–Tibetan plateau region at an altitude of over 4,000 m. However, a lack of genomic information has made it difficult to understand the high-altitude adaptation of these sheep. We sequenced and assembled the GD reference genome using PacBio, Hi-C, and Illumina sequencing technologies. The final assembled genome size was 2.73 Gb, with a contig N50 of 20.30 Mb and a scaffold N50 of 107.63 Mb. The genome is predicted to contain 20,759 protein-coding genes, of which 98.42 have functional annotations. Repeat elements account for approximately 52.2% of the genomic landscape. The completeness of the GD genome assembly is highlighted by a BUSCO score of 93.1%. This high-quality genome assembly provides a critical resource for future molecular breeding and genetic improvement of Tibetan sheep. [ABSTRACT FROM AUTHOR]

The identification of genome-wide selection signatures can reveal the potential genetic mechanisms involved in the generation of new breeds through natural or artificial selection. In this study, we screened the genome-wide selection signatures of prolific Suffolk sheep, a new strain of multiparous mutton sheep, to identify candidate genes for reproduction traits and unravel the germplasm characteristics and population genetic evolution of this new strain of Suffolk sheep. Whole-genome resequencing was performed at an effective sequencing depth of 20× for genomic diversity and population structure analysis. Additionally, selection signatures were investigated in prolific Suffolk sheep, Suffolk sheep, and Hu sheep using fixation index (FST) and heterozygosity H) analysis. A total of 5,236.338 Gb of high-quality genomic data and 28,767,952 SNPs were obtained for prolific Suffolk sheep. Moreover, 99 selection signals spanning candidate genes were identified. Twenty-three genes were significantly associated with KEGG pathway and Gene Ontology terms related to reproduction, growth, immunity, and metabolism. Through selective signal analysis, genes such as ARHGEF4, CATIP, and CCDC115 were found to be significantly correlated with reproductive traits in prolific Suffolk sheep and were highly associated with the mTOR signaling pathway, the melanogenic pathway, and the Hippo signaling pathways, among others. These results contribute to the understanding of the evolution of artificial selection in prolific Suffolk sheep and provide candidate reproduction-related genes that may be beneficial for the establishment of new sheep breeds. [ABSTRACT FROM AUTHOR]

Visna/Maedi virus (VMV) is lentiviral disease of sheep responsible for severe production losses. Multiple genomic regions associated with infection were reported indicating genetic complexity. In this study, a combined genomewide approach using a high-density SNP array has been performed, comparing VMV-infected (n = 78) and non-infected (n = 66) individuals of the Valle del Belice breed. The serological tests showed a seroprevalence of 26%. The comparison among results from different approaches (GWAS, Fisher's exact test and the FST analysis) revealed two association signals: on OAR03 close to the GRIN2B gene and on OAR05 close to the TMEM232 gene. To the best of our knowledge, there has been no previous association between these genes and lentiviral infection in any species. The GRIN2B gene plays a role in pain response, synaptic transmission, and receptor clustering, while TMEM232 is involved in the development of immune-related disorders. The results highlighted new aspects of the genetic complexity related to the resistance/susceptibility to VMV in sheep, confirming that studies on different breeds can lead to different results. The ideal approach for validation of the markers identified in our study is to use samples from a population independent from the discovery population with the same phenotype used in the discovery stage. [ABSTRACT FROM AUTHOR]

Simple Summary: Subclinical mastitis is a common and economically significant disease that affects dairy sheep production. This study aims to develop and evaluate an advanced algorithmic approach that integrates thermal imaging, statistical texture analysis, and t-distributed stochastic neighbor embedding (t-SNE) to accurately detect subclinical mastitis in dairy sheep. This approach focuses on improving the accuracy and reliability of non-invasive subclinical mastitis detection by using more sophisticated algorithmic procedures than traditional temperature differential methods, thereby enhancing livestock management and animal health monitoring. Subclinical mastitis is a common and economically significant disease that affects dairy sheep production. Thermal imaging presents a promising avenue for non-invasive detection, but existing methodologies often rely on simplistic temperature differentials, potentially leading to inaccurate assessments. This study proposes an advanced algorithmic approach integrating thermal imaging processing with statistical texture analysis and t-distributed stochastic neighbor embedding (t-SNE). Our method achieves a high classification accuracy of 84% using the support vector machines (SVM) algorithm. Furthermore, we introduce another commonly employed evaluation metric, correlating thermal images with commercial California mastitis test (CMT) results after establishing threshold conditions on statistical features, yielding a sensitivity (the true positive rate) of 80% and a specificity (the true negative rate) of 92.5%. The evaluation metrics underscore the efficacy of our approach in detecting subclinical mastitis in dairy sheep, offering a robust tool for improved management practices. [ABSTRACT FROM AUTHOR]

Local livestock breeds play a crucial role in global biodiversity, connecting natural and human-influenced environments and contributing significantly to ecosystem services. While commercial breeds dominate industrial systems, local livestock breeds in developing countries, like Barbarine sheep in Tunisia, are vital for food security and community maintenance. The Tunisian Barbarine sheep, known for its adaptability and distinctive fat-tailed morphology, faces challenges due to historical crossbreeding. In this study, the Illumina Ovine SNP50K BeadChip array was used to perform a genome-wide characterization of Tunisian Barbarine sheep to investigate its genetic diversity, the genome structure, and the relationship within the context of Mediterranean breeds. The results show moderate genetic diversity and low inbreeding. Runs of Homozygosity analysis find genomic regions linked to important traits, including fat tail characteristics. Genomic relationship analysis shows proximity to Algerian thin-tailed breeds, suggesting crossbreeding impacts. Admixture analysis reveals unique genetic patterns, emphasizing the Tunisian Barbarine's identity within the Mediterranean context and its closeness to African breeds. Current results represent a starting point for the creation of monitoring and conservation plans. In summary, despite genetic dilution due to crossbreeding, the identification of genomic regions offers crucial insights for conservation. The study confirms the importance of preserving unique genetic characteristics of local breeds, particularly in the face of ongoing crossbreeding practices and environmental challenges. These findings contribute valuable insights for the sustainable management of this unique genetic reservoir, supporting local economies and preserving sheep species biodiversity. [ABSTRACT FROM AUTHOR]

Introduction: Improving ewe longevity is an important breeding and management goal, as death loss and early culling of mature ewes are economic burdens in the sheep industry. Ewe longevity can be improved by selecting for positive reproductive outcomes. However, the breeding approaches for accomplishing this come with the challenge of recording a lifetime trait. Characterizing genetic factors underpinning ewe longevity and related traits could result in the development of genomic selection strategies to improve the stayability of sheep through early, informed selection of replacement ewes. Methods: Towards this aim, a genome-wide association study (GWAS) was performed to identify genetic markers associated with ewe longevity, reproductive, and production traits. Traits evaluated included longevity (i.e., length of time in the flock), parity and the lifetime number of lambs born, lambs born alive, lambs weaned, and weight of lambs weaned. Ewe records from previous studies were used. Specifically, Rambouillet (n = 480), Polypay (n = 404), Suffolk (n = 182), and Columbia (n = 64) breed ewes (N = 1,130) were analyzed against 503,617 SNPs in across-breed and within-breed GWAS conducted with the Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) model in R. Results: The across-breed GWAS identified 25 significant SNPs and the withinbreed GWAS for Rambouillet, Polypay, and Suffolk ewes identified an additional 19 significant SNPs. The most significant markers were rs411309094 (13: 22,467,143) associated with longevity in across-breed GWAS (p-value = 8.3E13) and rs429525276 (2:148,398,336) associated with both longevity (p-value = 6.4E-15) and parity (p-value = 4.8E-15) in Rambouillet GWAS. Significant SNPs were identified within or in proximity (±50 kb) of genes with known or proposed roles in reproduction, dentition, and the immune system. These genes include ALPL, ANOS1, ARHGEF26, ASIC2, ASTN2, ATP8A2, CAMK2D, CEP89, DISC1, ITGB6, KCNH8, MBNL3, MINDY4, MTSS1, PLEKHA7, PRIM2, RNF43, ROBO2, SLCO1A2, TMEM266, TNFRSF21, and ZNF804B. Discussion: This study proposes multiple SNPs as candidates for use in selection indices and suggests genes for further research towards improving understanding of the genetic factors contributing to longevity, reproductive, and production traits of ewes. [ABSTRACT FROM AUTHOR]