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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.

International audience; One strategy for improving fertility in cattle is administration of GnRH or human chorionic gonadotropin (hCG) during the luteal phase, which increases progesterone (P4) secretion and delays luteolysis. To provide an overview of how GnRH or hCG treatment between 4 and 15 d after artificial insemination (AI) improves pregnancy per AI (P/AI) in cows, a meta-analysis was performed on 107 different trials from 52 publications. Data from 18,082 treated cows and 18,385 untreated controls were meta-analyzed. The meta-analysis explained the relative risk for P/AI with GnRH or hCG treatment under various circumstances. The results did not show any difference in P/AI between cows treated with hCG and cows treated with GnRH. Compared with no treatment, treatment with GnRH or hCG improved the chances of P/AI in cows with very poor (60.1%). Moreover, treatment with GnRH and hCG improved the chances of P/AI in primiparous cows. The improvement was much better in primiparous cows with very low fertility. Treatment with buserelin at a dose above 10 p,g and with hCG at a dose above 2,500 IU was associated with increased chances of P/AI compared with lower doses. Treatment with GnRH 10 d after AI was also associated with increased chances of P/AI compared with earlier treatment. The present meta-analysis showed that the use of GnRH and hCG after AI should be focused on cows expected to have low or moderate fertility. Day and dose of treatment have to be considered as well.

Northwest-African sheep represent an ideal case-study for assessing the potential impact of genetic homogenization as a threat to the future of traditional breeds that are adapted to local conditions. We studied ten Algerian and Moroccan breeds of sheep, including three transboundary breeds, distributed over a large part of the Maghreb region, which represents a geographically and historically coherent unit. Our analysis of the dataset that involved carrying out Genome-wide SNP genotyping, revealed a high level of homogenization (ADMIXTURE, NetView, fineSTRUCTURE and IBD segments analyses), in such a way that some breeds from different origins appeared genetically undistinguished: by grouping the eight most admixed populations, we obtained a mean global FST value of 0.0024. The sPCA analysis revealed that the major part of Morocco and the Northern part of Algeria were affected by the phenomenon, including most of the breeds considered. Unsupervised cross-breeding with the popular Ouled-Djellal breed was identified as a proximate cause of this homogenization. The issue of transboundary breeds was investigated, and the Hamra breed in particular was examined via ROH fragments analysis. Genetic diversity was considered in the light of historical archives and anthropological works. All of these elements taken together suggest that homogenization as a factor affecting the Maghrebin sheep stock, has been particularly significant over the last few decades, although this process probably started much earlier. In particular, we have identified the policies set by the French administration during the colonial period of the region’s history as a causal factor that probably contributed significantly to this process. The genetic homogenization that we have observed calls into question the integrity of the farm animal genomic resources represented by these local breeds, whose conservation is of critical importance to the future of the livestock sector.

International audience; 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, F-ST), 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 F-ST, 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.

International audience; In developing countries, cross-breeding between local breeds and indigene or exotic breeds represents one of the main threats to the livestock diversity, leading to genetic dilution and loss of unique allelic combination underlying essential local adaptive traits. In this study, two Algerian sheep breeds, known to be highly admixed, were considered as a case study, to demonstrate how combination of different methodologies coupled with the use of specific softwares can be efficient to assess the spatial structuration of a hybrid zone, even in a case of extreme admixture. A fine sampling covering distribution areas of both breeds was implemented in order to study the admixture area and adjacent zones from a phenotypic (i.e., 19 quantitative traits were considered) and a genetic point of view (i.e., 21 microsatellites markers were used). Both approaches gave concordant patterns, highlighting areas with sheep most differentiated (or less admixed) for each breed. In detail, the region of Biskra appeared as the most preserved for the Ouled-Djellal breed and the northwest of Laghouat was identified as the most preserved area for the Rembi breed. The approach proposed in the study offers a low-cost solution to identify the most representative flocks of a breed, allowing the implementation of efficient conservation plans.

In order to optimize luteal function by human chorionic gonadotrophin (hCG) or gonadotrophin releasing hormone (GnRH) on day 11 after artificial insemination (AI). 33 cows synchronized by the Ovsynch and divided into 3 groups according to the type of treatment: 1) hCG (1500 IU, n=11); 2) GnRH (100 µg, n=11); and 3) control (2 mL of saline, n=11). Blood samples were collected from all animals every 3 days from day 5 to day 23 to determine progesterone concentration. Ultrasonography was used to monitor the luteal surface structures at the time of blood sample collection. An accessory corpus luteum (CL) formed in 63.63% of cows treated with GnRH and with hCG, resulting in an increase in the total luteal tissue area compared with the controls. Thus, the volume of the principal CL was increased by hCG but tended to be similar to GnRH compared with the controls. Additionally, compared with the control group, hCG-treated and GnRH-treated cows had increased progesterone concentrations (p

International audience; Genomic regions subjected to selection frequently show signatures such as within-population reduced nucleotide diversity and outlier values of differentiation among differentially selected populations. In this study, we analyzed 50K SNP genotype data of 373 animals belonging to 23 sheep breeds of different geographic origins using the Rsb (extended haplotype homozygosity) and FST statistical approaches, to identify loci associated with the fat-tail phenotype. We also checked if these putative selection signatures overlapped with regions of high-homozygosity (ROH). The analyses identified novel signals and confirmed the presence of selection signature in genomic regions that harbor candidate genes known to affect fat deposition. Several genomic regions that frequently appeared in ROH were also identified within each breed, but only two ROH islands overlapped with the putative selection signatures. The results reported herein provide the most complete genome-wide study of selection signatures for fat-tail in African and Eurasian sheep breeds; they also contribute insights into the genetic basis for the fat tail phenotype in sheep, and confirm the great complexity of the mechanisms that underlie quantitative traits, such as the fat-tail.