No abstract

Knowledge of population structure is essential to improve the management and conservation of farm animal genetic resources. Microsatellites, which have long been popular for this type of analysis, are more and more neglected in favor of whole-genome single nucleotide polymorphism (SNP) chips that are now available for the main farmed animal species. In this study, we compared genetic patterns derived from microsatellites to that inferred by SNPs, considering three pairs of datasets of sheep and cattle. Population genetic differentiation analyses (Fixation index, FST), as well as STRUCTURE analyses showed a very strong consistency between the two types of markers. Microsatellites gave pictures that were largely concordant with SNPs, although less accurate. The best concordance was found in the most complex dataset, which included 17 French sheep breeds (with a Pearson correlation coefficient of 0.95 considering the 136 values of pairwise FST, obtained with both types of markers). The use of microsatellites reduces the cost and the related analyses do not require specific computer equipment (i.e., information technology (IT) infrastructure able to provide adequate computing and storage capacity). Therefore, this tool may still be a very appropriate solution to evaluate, in a first stage, the general state of livestock at national scales. At a time when local breeds are disappearing at an alarming rate, it is urgent to improve our knowledge of them, in particular by promoting tools accessible to the greatest number.

Le cheptel ovin algérien reste méconnu, malgré son intérêt économique et les qualités très précieuses des races locales qui montrent des adaptations exceptionnelles dans des conditions environnementales extrêmes. La variabilité phénotypique de la Rembi, race algérienne menacée, a été étudiée au moyen d’une analyse discriminante multivariée. L’échantillonnage a pris en considération la diversité des environnements de production présents dans le pays selon les recommandations de la FAO. Au total 722 femelles et 60 mâles ont été phénotypés sur une grande zone incluant le berceau de la race, en utilisant 21 variables quantitatives et 12 variables qualitatives. Les résultats montrent une forte homogénéité phénotypique qui suggère une homogénéité intraraciale au niveau génétique, à confirmer par des analyses moléculaires. En effet, aucune structuration phénotypique n’a été mise en évidence, que ce soit en considérant le statut de la ferme (privée/étatique), la zone climatique (aride/semi-aride/subhumide), la mobilité du troupeau (sédentaire/semi-sédentaire/transhumant) ou encore la variété. Seule la considération du facteur région a permis la mise en évidence de sous-groupes au sein de la race. Les échanges commerciaux, organisés autour de marchés principaux, favorisent les flux d’individus à l’intérieur des différentes régions et semblent responsables d’un modèle phénotypique unique. Ces résultats permettent pour la première fois de caractériser finement la Rembi. Les indices morphologiques la situent notamment parmi les races à viande. Cette étude est la première étape vers la mise en place de programmes de conservation de cette race très menacée par des croisements avec la Ouled-Djellal, la race algérienne dominante.

Livestock is heavily affected by trypanosomosis in Africa. Through strong selective pressure, several African indigenous breeds of cattle and small ruminants have acquired varying degrees of tolerance against this disease. In this study, we combined LFMM and PCAdapt for analyzing two datasets of goats from West-Central Africa and East Africa, respectively, both comprising breeds with different assumed levels of trypanotolerance. The objectives were (i) to identify molecular signatures of selection related to trypanotolerance; and (ii) to guide an optimal sampling for subsequent studies. From 33 identified signatures, 18 had been detected previously in the literature as being mainly associated with climatic adaptations. The most plausible signatures of trypanotolerance indicate the genes DIS3L2, COPS7B, PD5A, UBE2K, and UBR1. The last gene is of particular interest since previous literature has already identified E3-ubiquitin ligases as playing a decisive role in the immune response. For following-up on these findings, the West-Central African area appears particularly relevant because of (i) a clear parasitic load gradient related to a humidity gradient, and (ii) still restricted admixture levels between goat breeds. This study illustrates the importance of protecting local breeds, which have retained unique allelic combinations conferring their remarkable adaptations.

An 11-year survey conducted in the wilayas of Djelfa, Msila and Biskra reveals two contrasting flock management strategies adopted by Ouled Djellal sheep breeders, shaped by ecological as well as economic factors. Breeders in Djelfa raise an average of 12 ewes per ram, while those in Msila and Biskra raise an average of 28 ewes per ram. This has led to a higher production of lambs/ewe/year in Djelfa than in the other two wilayas. To understand the significance of these strategies, two hypotheses were tested. According to ecology, we expected that in Djelfa, pasture productivity was higher than in the Biskra and M’sila, as a result of higher annual rainfall and hence pluviothermic coefficient Q3. We compared the altitudinal distribution of two stocking rates to pluviothermic coefficients. The ecological view was supported by higher Q3 in Djelfa than in Biskra and M’sila for higher stocking rates. However, the overall degradation of the steppe was, also, more pronounced in Djelfa than in the other two wilayas. In addition, GLM models have shown the impact of climatic parameters on the survival of lambs and adults. From an economic point of view, the higher lamb/ewe production in Djelfa is underpinned by increased marketing facilities, with: i) a strong demand for sheep by the inhabitants of the North, ii) a favorable geographical location, as Djelfa is crossed by the main roads of Algeria linking the South and the capital located in the North, and iii) the presence of the main sheep markets of the country. This study highlights the impact of environmental variables on the management practices of livestock farmers, and points the way for further studies of this type, which are essential as practices will have to adapt to climate change.

In order to characterize the production of sheep milk in Algeria (North of Africa) and to detect molecular markers related to the constitution of the protein phase of this milk, we proposed to analyze the electrophoretic behaviors of caseins and serum proteins under various migration conditions (native, urea and SDS-PAGE), from milk collected during the first three months of the year, from two breeds Ouled-Djellal and Rembi, living in the central area steppe. The profiles obtained show a great similarity and homogeneity between the different samples of the milk of the two breeds of ewes studied as to the number and intensity of the revealed migration bands. Some of the latter are nevertheless distinguished from cow’s milk by different levels of migration and intensity, which require partial sequencing to be able to identify them with certainty.