Sheep Breeds Research Articles

Analysis of genetic variants for different horn phenotypes and their inheritance in Icelandic sheep

Abstract. Icelandic sheep are characterized by a great diversity in horn phenotypes. Within their breed, they show a variability in terms of this trait to an extent rarely observed elsewhere. Previously, several genetic variants were published as markers for horn status (in terms of absence or presence of horns, including scurs) and horn traits (e.g., oval horns, horn length and polyceraty). The aim of this study was to genotype, for the first time, five of these genetic variants in Icelandic sheep with different horn phenotypes, as well as to analyze their inheritance. Phenotypic and pedigree data, as well as DNA samples from two Icelandic sheep farms, were used. Genetic variants were genotyped by published PCR-based methods in all samples (n=94) or in subsets. As in other sheep breeds with variable horn status, the inheritance of the presence or absence of horns was shown to be complex in Icelandic sheep, especially when sheep carry anything other than regularly formed horns. The 1.78 kb sized RXFP2 insertion on ovine chromosome 10 previously described to be associated with polledness in several sheep breeds was also found to be present in Icelandic sheep and showed some association but not a perfect segregation with the individuals' horn statuses. Missing associations were especially seen in sheep with scurs and oval horns. Regarding horn shape, there was no agreement with the studied variants described in Chinese breeds having comparable horn traits. However, matching tendencies were seen for the horn size variant that was found in the same study. All sheep with four or more horns carried the already published 4 bp deletion in HOXD1, as previously described for three other sheep breeds. Interestingly, for the first time, the deletion was also detected in phenotypically polled animals originating from multi-horned families. According to the results from animals genotyped simultaneously for the RXFP2 and the HOXD1 variants, polledness in sheep with a genetic disposition for polyceraty seems not to be controlled by the RXFP2 insertion. However, this and all other findings in Icelandic sheep need to be confirmed by analyzing a higher number of well-phenotyped animals.

Increasing GSH-Px Activity and Activating Wnt Pathway Promote Fine Wool Growth in FGF5-Edited Sheep.

Fibroblast growth factor 5 (FGF5) plays key roles in promoting the transition from the anagen to catagen during the hair follicle cycle. The sheep serves as an excellent model for studying hair growth and is frequently utilized in various research processes related to human skin diseases. We used the CRISPR/Cas9 system to generate four FGF5-edited Dorper sheep and only low levels of FGF5 were detected in the edited sheep. The density of fine wool in GE sheep was markedly increased, and the proportion of fine wool with a diameter of 14.4-20.0 μm was significantly higher. The proliferation signal in the skin of gene-edited (GE) sheep was stronger than in wild-type (WT) sheep. FGF5 editing decreased cortisol concentration in the skin, further activated the activity of antioxidant enzymes such as Glutathione peroxidase (GSH-Px), and regulated the expression of Wnt signaling pathways containing Wnt agonists (Rspondins, Rspos) and antagonists (Notum) in hair regeneration. We suggest that FGF5 not only mediates the activation of antioxidant pathways by cortisol, which constitutes a highly coordinated microenvironment in hair follicle cells, but also influences key signals of the Wnt pathway to regulate secondary hair follicle (SHF) development. Overall, our findings here demonstrate that FGF5 plays a significant role in regulating SHF growth in sheep and potentially serves as a molecular marker of fine wool growth in sheep breeding.

Evaluating serum electrolyte and trace element variations between Babesia ovis-infected and uninfected Lohi sheep

Babesiosis caused by Babesia ovis is a major threat to the livestock industry worldwide. In Pakistan, the Lohi sheep breed is an important economic resource, but limited information is available on the impact of B. ovis infection on this breed. This study aimed to investigate the serum electrolyte and trace element variations between B. ovis-infected and uninfected Lohi sheep from Pakistan. A total of 97 Lohi sheep was stratified based on the geographical distribution of Multan district, employing a multistage cluster sampling method. Blood and serum samples were collected from randomly selected sheep, and DNA extraction and PCR amplification were performed to detect B. ovis infection. Serum electrolyte and trace element levels were analyzed in infected (n=67) and uninfected (n=30) groups, stratified by age and gender. The study revealed a 69.07% overall infection rate of B. ovis in Lohi sheep. Infected sheep showed significantly elevated serum copper levels (p<0.0001), with no substantial differences observed in serum iron, sodium, potassium, and chloride levels. However, age-wise variance analysis revealed statistically significant variations in sodium and potassium levels (p<0.0001 and p<0.05, respectively). Notably, serum chloride levels differed between infected and uninfected females in individuals younger than two years (p<0.05). Serum iron levels remained consistent across different age groups. Comparative analysis indicated a higher prevalence of electrolyte imbalances, such as hyponatremia, hyperkalemia, hyperchloremia, and hypoferremia, in infected sheep compared to normal reference ranges, while instances of hypernatremia, hypokalemia, hypochloremia, and hyperferremia were less frequent. In conclusion, our study suggests that B. ovis infections could lead to alterations in serum electrolyte and trace element levels in Lohi sheep, emphasizing the importance of further research into the specific mechanisms driving these alterations to enhance disease management strategies tailored to this breed.

Investigation of the Thermodynamic and Kinetic Behavior of Acid Dyes in Relation to Wool Fiber Morphology.

Wool fibers from several different sheep breeds in the UK have very limited applications. The main aim of this study was to establish an understanding of the dye sorption properties of different wool fibers through thermodynamics and kinetics of dyeing using Acid Red 1 dye. Wool fibers from Leicester, Ryeland, and Dartmoor sheep breeds were pretreated (to remove impurities) and dyed using Acid Red 1. Leicester showed 7% higher dye exhaustion than Dartmoor wool fibers (20% on mass of fiber). Dyeing equilibrium results for both Leicester and Dartmoor wool fibers were fitted to Langmuir and Freundlich isotherms, and the theoretical maximum sorption capacities were 164 and 144 mg g-1, respectively. Leicester, Ryeland, and Dartmoor also followed the pseudo-second-order reaction kinetics. Thermodynamic parameters like Gibb's free energy (ΔG°) and standard affinity (Δμ°) of the fibers were calculated to understand the interaction of the Acid Red 1 with wool fibers. The difference in dye uptake was explained through the possible involvement of the scale opening gap (surface morphology) of the wool fibers.

Prevalence of Gastrointestinal Parasites in Small Ruminant Farms in Southern Spain.

The primary population of small ruminants in Spain is concentrated in the southern region, a critical area for the country's livestock production. Indirect economic losses can occur when this livestock is affected by gastrointestinal parasites. This study aimed to determine the prevalence of these parasites in small ruminant herds (159 sheep and 39 goats) through coprological analyses and conducted a survey on farmers' management practices related to gastrointestinal parasite control. The survey results revealed some important aspects: monitoring through coprological analyses is not a common practice; veterinarians are not typically involved in deworming plans; anthelmintic treatment in adults is often applied twice a year in sheep and once a year in goats; and finally, drug rotation was higher in sheep farms. Coprological analyses showed Eimeria spp. as the most common parasitic infection, followed by Strongyles infection. Other parasites like Moniezia spp., Trichuris spp., and D. dendriticum were less important, although their prevalence was higher in sheep than goats. This constitutes the first report on the epidemiological status of gastrointestinal parasites in small ruminants in southern Spain. Based on the survey findings, the introduction of certain management measures on farms could potentially mitigate parasite infections.

Biotechnological methods for improving reproduction on sheep breeding program using laparoscopic artificial inseminations in Debrecen, Hungary

The aim of this study was to evaluate the results of the LAI method in different types of breeds and seasonal variations. Analysing n=536 LAI in 7 years, there were no significant differences observed in the breed in lambing rates. Although the lambing rate of Prolific Merino (F+) was better than any other breed (45.3%). We found significant differences between breeds of Tzigaia, its pregnancy rate was 19.2%. In the case of prolificacy there were significant differences between breeds: Prolific Merino’s (FF) was the highest (2.38) and, Indigenous Tzigaia’s was the lowest (1.4) from all of them. The obtained results showed that summer inseminations were the most effective in concern of pregnancy rate (49.5%). The results are based on use of the types of semen, showed that using frozen semen was most effective than fresh semen in both parameters, however there were no significant differences. Summarising all tested conditions in our study breeds, seasons and type of semen using LAI the total results of pregnancy rate was 40.3% and the prolificacy was 1.78, respectively. Follow up the out-of-season ovarian, progesterone level of n=36 Prolific Merino were examined and insulin, IGF-1, leptin, T3, and T4 hormones as well, to evaluate the energetic status of the flock. Progesterone analysis showed 43% of examined ewes had a cyclical ovarian function in April and a cyclical ones had good reaction for estrus-induction hormonal treatment. Our results showed that valuable information can be obtained about energy supply from the determination of some metabolic hormones as IGF-1, insulin, leptin.

The status of conservation and management of indigenous sheep breeds in South Africa - A review

Indigenous sheep breeds in South Africa play an important role in local food security and they are adapted to local conditions. Their genetic and cultural values have to be recognised for national importance. The conservation of these breeds is very critical as most of them are already classified as endangered. The South African government has the initiative to attempt the conservation of these animals; however, it comes with several challenges. In addition to funding, breed conservation demands farmers to understand and recognise the role of such breeds in society. This is especially crucial in the rural communal lands where breeds are kept. Farmers that raise indigenous breeds should be taught the necessity of maintaining the purity of these breeds. Indigenous sheep breeds in South Africa are not favored by the commercial farmers and thus they are more vulnerable. This review outlines the nature of sheep farming and the conservation status of four indigenous sheep breeds in South Africa. The effort and challenges that are met in current conservation arrangements are discussed. Moreover, we emphasise on the conservation techniques that are employed in South Africa.

Meningoencephalitic Listeriosis in Iranian Sheep and Goats

Background: Meningoencephalitic listeriosis is a significant disease affecting goats and sheep, with potential implications for public health. This study aimed to investigate and report the occurrence, clinical manifestation, laboratory findings, and further understanding of neurolisteriosis in the goat and sheep populations in Tehran, Qazvin, and Kurdistan provinces of Iran. Methods: From 2018 to 2021, a program was implemented to monitor multiple flocks for meningoencephalitic listeriosis. Clinical manifestations of animals that showed suspected neurological signs of listeriosis (19 animals) were recorded, and necropsies were performed. Sampling of the brain tissue of infected animals was done. The specimens underwent a 'cold-enrichment' procedure, and subsequent culture and biochemical tests were conducted to confirm the presence of Listeria monocytogenes. Results: According to the clinical and bacteriological findings, 19 animals were diagnosed with neurolisteriosis. The affected animals exhibited various signs of the disease, including head deviation, head tilt, head pressing, mouthfuls, walking in circles, drooping of the ear, and unilateral hypalgesia. L. monocytogenes was isolated from brain samples of 11 animals. Conclusion: The study revealed potential indications of meningoencephalitic listeriosis in certain breeds of goats and sheep. Recognizing these typical signs can contribute to early detection, diagnosis, and proper management of listeriosis cases, improving welfare and health outcomes for affected animals. The results underscore the importance of strengthened disease surveillance, prevention, and control strategies.

Effects of dietary curcumin nano-micelles on performance, biological responses, and thermal stress resilience in heat-stressed fattening lambs across varying temperature-humidity index conditions: Implications for climate change

Heat stress poses a significant challenge to sheep farming in arid and semi-arid regions, impacting growth performance, health, and physiological responses. While sheep have innate mechanisms to manage heat stress, prolonged exposure impairs their performance and health. This study evaluated the influence of varying doses of Curcumin Nano-Micelle (CNM) on heat-stressed fattening lambs in northeastern Iran over three months, examining the relationship between CNM doses and growth performance, feeding behavior, physiological responses, immune function, and antioxidant status. Thirty-two crossbred male lambs were included in a completely randomized design with four treatments and eight replications. The experimental treatments were as follows: 1) CTRL: No dietary inclusion of CNM, (control group); 2) T20: Dietary inclusion of 20 mg of CNM per head per day; 3) T40: Dietary inclusion of 40 mg of CNM per head per day; and 4) T80: Dietary inclusion of 80 mg of CNM per head per day. The results revealed that dietary supplementation with 20 and 40 mg of CNM significantly improved live body weight, weight gain, average daily gain (ADG), and feed conversion ratio (FCR) compared to the control treatment. Regression analysis demonstrated quadratic models between growth performance parameters and the Temperature-Humidity Index (THI), indicating a correlation between CNM doses and the animals' responses to heat stress. Regarding eating behavior, CNM doses of 40 and 80 mg/day significantly reduced eating time while increasing ruminating time. Blood analysis indicated significant reductions in glucose levels across all treatments, with T40 significantly reducing both cholesterol and triglyceride (TG) levels. Additionally, CNM supplementation decreased serum malondialdehyde (MDA) levels and increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, indicating enhanced antioxidant status. Physiological responses were influenced by CNM, notably reducing rectal temperature (RT), skin temperature (ST), respiration rate (RR), while pulse rate (PR) increased across various time intervals, particularly in the T80 group. This study demonstrates that CNM supplementation can enhance performance, physiological responses, and antioxidant status in heat-stressed fattening lambs, highlighting its potential to mitigate heat stress effects in sheep farming.

Seroprevalence of Q fever (Coxiella burnetii) in sheep in the Kwahu West municipality, Eastern Region, Ghana

Query fever, also known as Q fever, is a zoonotic disease caused by Coxiella burnetii. It is a cause of abortion in livestock and presents as a febrile illness in humans. A correlation between the incidence of the disease in humans and abortion in goats and sheep farms has been reported in countries such as the Netherlands and Australia. In Ghana, the occurrence of Q fever in both livestock and humans has not been fully explored. This study sought to determine the seroprevalence of Q fever in livestock in Nkawkaw, in the Eastern Region of Ghana. Sera obtained from 92 sheep from 12 farms were tested using the indirect multi-species ELISA for the detection of anti-Coxiella burnetii antibodies. Animal demographics, farms’ proximity to human settlement and history of abortion in relation to the Q fever status were assessed.The overall prevalence of Q fever was 13.0 % [95 % CI 6.9–21.6] (12/92). Both sexes were equally affected, with a sex-specific prevalence of 13.0 % each. The farm-specific prevalence was 50 %. Abortions were reported on eight (8) of the 12 farms, and all farms were located less than 200 m from human habitation. Only proximity of farm to human settlement showed statistical significance. Q fever is prevalent in Nkawkaw and requires the attention of both animal and health authorities, using the One- Health approach to nip any future epidemics in its bud.

Boyhood Among the Woolies: Growing Up on a Basque Sheep Ranch by Richard W. Etulain (review)

Boyhood Among the Woolies: Growing Up on a Basque Sheep Ranch by Richard W. Etulain (review)

Microbial Evolution in Artisanal Pecorino-like Cheeses Produced from Two Farms Managing Two Different Breeds of Sheep (Comisana and Lacaune).

"Pecorino" is a typical semi-hard cheese obtained with raw or heat-treated sheep milk using procedures to valorize the raw material's chemical and microbiological properties. In the present study, using a high-throughput method of 16S rRNA gene sequencing, we assessed the evolution of the microbiome composition from milk to Pecorino-like cheese in artisanal processes using milk from Comisana and Lacaune sheep breeds. The comparative analysis of the bacterial community composition revealed significant differences in the presence and abundance of specific taxa in the milk microbiomes of the Comisana and Lacaune breeds. Next-Generation Sequencing (NGS) analysis also revealed differences in the curd microbiomes related to dairy farming practices, which have a relevant effect on the final structure of the Pecorino cheese microbiome.

Skeletal muscle transcriptomics of sheep acclimated to cold desert and tropical regions identifies genes and pathways accentuating their diversity.

The current study attempts to investigate the differences in gene expression in longissimus thoracis muscles between sheep breeds acclimated to diverse environments. Changthangi sheep inhabits the cold arid plateau of Ladakh, at an altitude above 3000m with prevalence of rarefied atmosphere. Muzzafarnagri sheep, on the other hand is found in the sub-tropical hot and humid plains at an altitude of about 250m. Comparative transcriptomics was used to provide a molecular perspective of the differential adaptation of the two breeds. RNA sequencing data was generated from four biological replicates of the longissimus thoracis muscles from both breeds. The common genes expressed in both breeds were involved in muscle contraction and muscle fibre organization. The most significant pathways enriched in Changthangi muscles were glycogen metabolism, reduction of cytosolic Ca++ levels and NFE2L2 regulating anti-oxidant, while those in Muzzafarnagri were extracellular matrix organization and collagen formation. The hub genes identified in Changthangi were involved in hematopoiesis and HIF signaling pathway, suggesting the molecular acclimatization of Changthangi to the high altitude cold desert of Ladakh. The nodal genes discovered in Muzzafarnagri sheep were associated with the extracellular matrix which accentuates its significance in the development, growth and repair of muscles. The observed transcriptomic differences underscore the morphological and adaptive disparity between the two breeds. The candidate genes and pathways identified in this study will form the basis for future research on adaptation to high altitude and body size in small ruminants.

The Detection of a Functional 168 bp Deletion of the HOXB13 Gene Determining Short Tail and Its Association with Senior Growth Traits in Sheep Breeds Worldwide.

In recent years, genome-wide association studies (GWAS) have uncovered that the HOXB13 gene is a key regulatory factor for the tail length trait of sheep. Further research has found that there is a functional 168 bp SINE element insertion upstream of the HOXB13 gene, which leads to the occurrence of long tails in sheep. However, the frequency of mutations in the 168 bp SINE element of the HOXB13 gene among different sheep breeds around the world and its relationship with growth traits are still unclear. This study used whole-genome sequencing (WGS) data, including 588 samples from 33 different sheep breeds around the world, to evaluate the frequency of HOXB13 gene mutations in different sheep breeds globally. At the same time, this study also selected 3392 sheep samples from six breeds. The genetic variation in the 168 bp InDel locus in the HOXB13 gene was determined through genotyping, and its association with the growth traits of Luxi black-headed sheep was analyzed. The research results indicate that the polymorphism of the 168 bp InDel locus is significantly correlated with the hip width of adult ewes in the Luxi black-headed sheep breed (p < 0.05) and that the hip width of adult ewes with the DD genotype is significantly larger than that of adult ewes with the ID genotype (p < 0.05). This study indicates that there is consistency between the research results on the sheep tail length trait and growth traits, which may contribute to the promotion of sheep breed improvement.

Identifying selection strategies based on the practices and preferences of small ruminant farmers to improve the sustainability of their breeding systems

Small ruminant farming is of socio-economic and environmental importance to many rural communities around the world. The SMARTER H2020 project aims to redefine genetic selection criteria to increase the sustainability of the sector. The objective of this study was to analyse the selection and breeding management practices of small ruminant producers and breeders, linked with socio-technical elements that shape them. The study is based on farm surveys using semi-structured interviews conducted in five countries (France, Spain, Italy, Greece, and Uruguay) across 272 producers and breeders of 13 sheep and goat breeds, and 15 breed × system combinations. The information was collected in four sections. The first and second sections dealt with general elements of structure and management of the system and the flock/herd. The third section focused on selection and breeding management practices: criteria for culling and replacement of females, selection criteria for males, use of estimated breeding values and global indexes, and preferences for indexing new traits to increase the sustainability of their system. The fourth section aimed to collect socio-technical information. We used a data abstraction method to standardise the representation of these data. A mixed data factor analysis followed by a hierarchical ascending classification allowed the characterisation of three profiles of selection and breeding management: (1) a profile of producers (n = 93) of small flocks/herds, with little knowledge or use of genetic selection and improvement tools (selection index, artificial insemination, performance recording); these farmers do not feel that new traits are needed to improve the sustainability of their system. (2) a profile of producers (n = 34) of multibreed flocks/herds that rely significantly on grazing; they are familiar with genetic tools, they currently use AI; they would like the indexes to include more health and robustness characteristics, to make their animals more resistant and to increase the sustainability of their system. And (3) a profile of producers or breeders (n = 145) of large flocks/herds, with specific culling criteria; these farmers are satisfied with the current indexes to maintain the sustainability of their system. These results are elements that can be used by private breeding companies and associations to support the evolution of selection objectives to increase the resilience of animals and to improve the sustainability of the small ruminant breeding systems.

Use of data mining algorithms to predict body weight of Dorper sheep Breed in two selected villages of Lepelle-Nkumpi local municipality in Limpopo province, South Africa

Sheep farmers in village areas find it difficult to estimate body weight without the weighing tools. The best fitted model for estimation of sheep body weight is not conclusive. Classification and regression tree (CART), Chi-square automatic interaction detection (CHAID), Exhaustive chi-square automatic interaction detection (Ex-CHAID) and Multivariate adaptive regression spline (MARS) were used to predict body weight (BW) of 306 Dorper sheep (female = 244 and male = 62) aged 1 to 2 years from linear body measurement traits such as rump height (RH), rump length (RL), heart girth (HG), withers height (WH), and body length (BL). Goodness of fit criteria's such as Pearson's correlation coefficients (r), coefficient of determination (R2), Akaike's information criterion AIC and adjusted R2 (Adj.R2) were computed for data mining algorithms performance assessment. The results indicated that MARS was the best data mining algorithm with r of 0.979, R2 of 0.958, Adj.R2 of 0.957, RMSE of 2.503 and AIC of 422.25. The MARS model provided the most appropriate predictive capability in the prediction of body weight for Dorper sheep with HG, WH, RH, BL, and sex (male) as the important traits. As a result, MARS data mining algorithm might be used to identify factors that might be vital to improve body weight of Dorper sheep for breeding programs.

Ancient Sheep Genomes Reveal Four Millennia of North European Short-Tailed Sheep in the Baltic Sea Region.

Sheep are among the earliest domesticated livestock species, with a wide variety of breeds present today. However, it remains unclear how far back this diversity goes, with formal documentation only dating back a few centuries. North European short-tailed (NEST) breeds are often assumed to be among the oldest domestic sheep populations, even thought to represent relicts of the earliest sheep expansions during the Neolithic period reaching Scandinavia <6,000 years ago. This study sequenced the genomes (up to 11.6X) of five sheep remains from the Baltic islands of Gotland and Åland, dating from the Late Neolithic (∼4,100 cal BP) to historical times (∼1,600 CE). Our findings indicate that these ancient sheep largely possessed the genetic characteristics of modern NEST breeds, suggesting a substantial degree of long-term continuity of this sheep type in the Baltic Sea region. Despite the wide temporal spread, population genetic analyses show high levels of affinity between the ancient genomes and they also exhibit relatively high genetic diversity when compared to modern NEST breeds, implying a loss of diversity in most breeds during the last centuries associated with breed formation and recent bottlenecks. Our results shed light on the development of breeds in Northern Europe specifically as well as the development of genetic diversity in sheep breeds, and their expansion from the domestication center in general.

Populations of Tuvan Shot-Fat-Tailed Sheep in the Structure of the Gene Pool of Sheep Breeds of the Russian Federation

Using 11 microsatellite markers (ОarCP49, INRA063, HSC, OarAE129, MAF214, OarFCB11, INRA005, SPS113, INRA23, MAF65, McM527), data were obtained on the levels of variability and degree of differentiation of 24 populations (1140 samples) of the Tuvan coarse-haired short-fat-tailed sheep of different regions of the Republic of Tyva and 24 breeds of sheep (721 samples) of various origins, covering the main sheep-breeding regions of the Russian Federation. During the analysis, a high level of genetic isolation and variability of Tuvan sheep was found, and in the general structure of Russian sheep breeds, a pronounced genetic divergence was revealed into two large groups, one of which unites fine-fleeced and semi-fine-fleeced sheep, and the other indigenous coarse-wooled breeds of North Caucasian and Asian origin

Integration of selective sweeps across the sheep genome: understanding the relationship between production and adaptation traits

BackgroundLivestock populations are under constant selective pressure for higher productivity levels for different selective purposes. This pressure results in the selection of animals with unique adaptive and production traits. The study of genomic regions associated with these unique characteristics has the potential to improve biological knowledge regarding the adaptive process and how it is connected to production levels and resilience, which is the ability of an animal to adapt to stress or an imbalance in homeostasis. Sheep is a species that has been subjected to several natural and artificial selective pressures during its history, resulting in a highly specialized species for production and adaptation to challenging environments. Here, the data from multiple studies that aim at mapping selective sweeps across the sheep genome associated with production and adaptation traits were integrated to identify confirmed selective sweeps (CSS).ResultsIn total, 37 studies were used to identify 518 CSS across the sheep genome, which were classified as production (147 prodCSS) and adaptation (219 adapCSS) CSS based on the frequency of each type of associated study. The genes within the CSS were associated with relevant biological processes for adaptation and production. For example, for adapCSS, the associated genes were related to the control of seasonality, circadian rhythm, and thermoregulation. On the other hand, genes associated with prodCSS were related to the control of feeding behaviour, reproduction, and cellular differentiation. In addition, genes harbouring both prodCSS and adapCSS showed an interesting association with lipid metabolism, suggesting a potential role of this process in the regulation of pleiotropic effects between these classes of traits.ConclusionsThe findings of this study contribute to a deeper understanding of the genetic link between productivity and adaptability in sheep breeds. This information may provide insights into the genetic mechanisms that underlie undesirable genetic correlations between these two groups of traits and pave the way for a better understanding of resilience as a positive ability to respond to environmental stressors, where the negative effects on production level are minimized.

Evaluation and use of recently introduced sheep breeds to Uruguay

Sheep numbers in Uruguay have declined over the last 30 years. In the north and northeast there are extensive wool and dual-purpose systems, respectively, where both wool and meat impact on income. In the south, small-scale family sheep meat production systems have flourished. In this thesis I report work pertaning to production systems in the south (1) and northeast (2) regions. Corriedale (C) is the predominant breed in the country. Milchschaf (M) has been disseminated in the south but C still prevails in the northeast. There is a paucity of rigorous evaluations of these breeds or alternatives that could be more profitable, such as Highlander (H) for the south and Dohne Merino (DM) for the northeast. I experimentally assessed: in 1), wool production, reproduction and growth in C, H and M, and in 2), wool quality and body traits in ewe hoggets from rotational crossbreeding between C and DM. In 1), wool production was better in C, but H and M outperformed C in live weight and reproductive performance. In 2), genotypes with greater proportions of DM produced lower fleece weight, and those with greater proportions of C produced coarser fibre diameter, with no differences in wool quality or morphological traits related to meat aptitude. Gross margins (GM) integrate physical performance with product values and costs, allowing monetary comparison between genotypes. I calculated GMs for a number of production and market scenarios. In 1), most often GM was greatest for H, followed by M. The differences in favor of H and M over C decreased when I considered higher feed requirements for H and M. The GM of H and M increased by assuming they were wool-less (the cost of harvesting exceeds the value of the wool produced). In 2), I considered low and high prices for wool of different fibre diameter. GM was greatest for ¾DM and ⅝DM at low prices, and for ¾DM and ½DM at high prices. C had the lowest GM in all scenarios. I recommend H for southern systems and research on hair sheep breeds. In extensive dual-purpose systems, rotational crossbreeding between C and DM allows for improved wool income without losing meat potential. I formulate recommendations about future genotype evaluations, integrating them with current within breed genetic evaluations.