Caracterisation Phenotypique de la Population Ovine du Sud Ouest de la Tunisie

Insight into the current genomic diversity, conservation status and population structure of Tunisian Barbarine sheep breed

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.

Genetic Characterization and Alternative Preservation Ways of Locally Adapted Sheep Breeds: Cases of Private and Public Sheep Sectors in Tunisia and Italy

Simple Summary

The genetic characterization of native sheep breeds from the Tunisian-Italian Mediterranean corridor, the earliest westward introduction route of sheep breeding from the domestication center, was carried out using microsatellite markers in order to compare the genetic diversity level between both Mediterranean sides’ local sheep breeds, and to investigate their level of risk for conservation purposes. Sampling concerned both private and public/institutional farms of all the native Tunisian breeds in the case of the southern Mediterranean side, and one center Italian and the Venetian native breeds from the northern side. The results revealed that the genetic diversity level of the Tunisian native breeds was higher than that of the Italian ones, with a lower inbreeding level. The comparison between private and public farms in terms of genetic diversity, consanguinity, and conservation decisions highlighted the superiority of the public/institutional breeding management strategies over private ones in both Tunisian and Italian cases. The present study illustrated the efficiency of genomic characterization in making genetic diversity evaluations and preservation decisions of native and well-adapted sheep breeds in both developing and developed countries’ rearing conditions.

Abstract

Non-commercialized sheep breeds known as local or native breeds are well adapted to their environmental constraints and constitute precious genetic resources that need prioritization for genetic diversity characterization and preservation. The aim of the present study was to assess the genetic diversity level and the related preservation decisions of very old and traditional native Mediterranean sheep breeds from Tunisia and Italy using 17 microsatellite markers. In total, 975 sheep were sampled from five Tunisian, one Center Italian, and four Venetian native breeds. Both private and publicly available farms were considered for each breed for breeding strategies’ comparison purposes. The microsatellite set used was highly informative (PIC = 0.80 ± 0.08), with a total of 383 alleles. Moderate genetic differentiation was revealed between the native sheep of the two Mediterranean sides (global overall loci F_ST = 0.081). The genetic diversity level was higher in the case of the Tunisian native breeds compared to the Italian ones, as evidenced by higher mean allelic richness, higher expected and observed heterozygosities, and lower inbreeding levels. Priority for conservation suggestions was carried out for each private or public breed population based on the contribution of each population to the diversity of the whole data. The four Venetian breeds, already undergoing conservation, the Tunisian dairy breed, and the very ancient Maghrebian breed, would be favored for conservation. In conclusion, our results highlighted the importance of the analyzed Mediterranean native sheep breeds as valuable inherited genetic reservoirs and supported previous conservation decisions made for the threatened breeds.

Historical Westward Migration Phases of Ovis aries Inferred from the Population Structure and the Phylogeography of Occidental Mediterranean Native Sheep Breeds

In this study, the genetic relationship and the population structure of western Mediterranean basin native sheep breeds are investigated, analyzing Maghrebian, Central Italian, and Venetian sheep with a highly informative microsatellite markers panel. The phylogeographical analysis, between breeds’ differentiation level (Wright’s fixation index), gene flow, ancestral relatedness measured by molecular coancestry, genetic distances, divergence times estimates and structure analyses, were revealed based on the assessment of 975 genotyped animals. The results unveiled the past introduction and migration history of sheep in the occidental Mediterranean basin since the early Neolithic. Our findings provided a scenario of three westward sheep migration phases fitting properly to the westward Neolithic expansion argued by zooarcheological, historical and human genetic studies.

Morphologic characterization of the Blanche de Montagne, an endemic sheep of the Atlas Mountains

The present study aims to investigate the morphological characteristics of the Blanche de Montagne sheep breed, mainly known by its long white fleece. The morphological characterization was performed on a total of 70 unrelated individuals of both sexes, having between 2 and 8 teeth and belonging to 13 farms located in the Ouarzazate region. The body measurements studied were body weight, body length, chest circumference, height at withers, rump height, chest depth, chest width, hip width, head length, head width, ear length, ear width, horn length, cannon circumference, wool length, and tail length. These measurements averaged 28.2±8.10 kg, 65.8±6.25 cm, 73.5±6.71 cm, 59.5±4.39 cm, 59.5±4.72 cm, 27.4±2.90 cm, 19.8±2.70 cm, 21.0±2.14 cm, 19.2±1.57 cm, 11.0±1.01 cm, 9.71±1.02 cm, 5.47±0.53 cm, 43.2±13.8 cm, 7.44±0.77 cm, 10.9±3.56 cm, and 31.8±4.36 cm, respectively. Descriptive statistics presented an overall coefficient of variation less than 15%, showing a homogeneous morphostructure of the breed. Most characters were small in relation with the low productivity of pastures. Moreover, 77.5% of correlation coefficients among the different body measurements were positive and significant, reflecting the strong morphological harmony of the breed, suggesting a long period of adaptation to its environment. The variance analysis showed that sex influenced the measurements, with males having the highest values. Similarly, individuals with 6 or 8 teeth showed higher values than those with 2 or 4 teeth. Through the comparison with other Moroccan breeds, the variation of some morphological traits was found in relation to some climatic parameters (mainly winter temperatures) and feeding supplementation.

Application of linear body measurements for predicting live weight in Ouled Djellal breed

The objective of this study was to predict the body weight of 66 females and 15 males Ouled Djellal breed aged over 2 years using fourteen simple linear body measurements and CREVAT formula. The total body length (TBDL), body length (BDL), scapular-ischial length (SIL), withers height (WH), heart girth (HG), chest depth (CD), paunch girth (PG), shoulder width (SW), hip-width (HW), trochanter width (TW), ischia width (IW), pelvis length (PL), cannon length (CL) and cannon perimeter (CP) were measured in centimeters, and body weight (BW) was determined in kilogram using a weighing scale. Results of the correlation coefficient showed that heart girth and the withers height were highly correlated with body weight (r = 0.93 and r =0.91 respectively), with variations by sex. Results of the stepwise regression showed that heart girth (HG), withers height (WH), scapular-ischiallength (SIL) and thecannon perimeter (CP) are the best prediction parameters of body weight in animals studied. From the CREVAT formula, the body weight was estimated by the HG (in meters): BW = 57.9 HG3. According to the different statistical methods used and the formula of CREVAT, we can conclude that body weight in Ouled Djellal breed can be estimated using simple linear body measurement of heart girth.